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Effects of exercise on stress : a meta-analysis Van Stavel, Rosemary 1991

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EFFECTS OF EXERCISE ON STRESS: A META-ANALYSIS by Rosemary van Stavel B . A . U n i v e r s i t y o f T o r o n t o , 1977 A T H E S I S SUBMITTED IN P A R T I A L F U L F I L M E N T OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF P H Y S I C A L EDUCATION i n THE F A C U L T Y OF GRADUATE STUDIES S c h o o l o f P h y s i c a l E d u c a t i o n a n d R e c r e a t i o n We a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d U N I V E R S I T Y OF B R I T I S H COLUMBIA J a n u a r y 1991 ROSEMARY VAN S T A V E L , 1991 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia Vancouver, Canada DE-6 (2/88) 11 A b s t r a c t P h y s i c a l e x e r c i s e i s f r e q u e n t l y p r e s c r i b e d by c l i n i c i a n s and researchers as an e f f e c t i v e s t r e s s r e d u c t i o n technique. There has been some research t o support t h i s a s s e r t i o n , however the research has been v a r i e d i n i t s methodological r i g o r . The design problems, v a r i a t i o n s i n e x e r c i s e programs, and the use of a wide range of p s y c h o l o g i c a l measures have made r e s u l t s d i f f i c u l t t o i n t e r p r e t . A d d i t i o n a l l y , the p s y c h o l o g i c a l b e n e f i t s and und e r l y i n g change processes have not been c l e a r l y d e l i n e a t e d . The purpose of t h i s study, was to conduct a meta-analysis of the research i n t h i s area i n an attempt t o answer s p e c i f i c questions regarding the r o l e of e x e r c i s e i n s t r e s s r e d u c t i o n . This meta-analytic approach was chosen because i t permits the q u a n t i t a t i v e i n t e g r a t i o n of f i n d i n g s of s e v e r a l s t u d i e s and c o n s i d e r a t i o n of the v a r i a b l e s t h a t may i n f l u e n c e the variance i n study outcomes. The e f f e c t i v e n e s s of e x e r c i s e as a treatment f o r s t r e s s , the typje of e x e r c i s e t h a t was most b e n e f i c i a l , and the ty p e ^ o f _ i n d i v i d u a l who gained the'most from the e x e r c i s e i n t e r v e n t i o n was examined. The 61 e f f e c t s i z e s , which were c a l c u l a t e d from 24 st u d i e s i n c l u d e d i n the meta-analysis, were coded along with other v a r i a b l e s considered important. Study components such as ^d^esjxf.q^t-y.pe.^ str.ess_leye.l-,-v_type. of .exercise program, program length, f r e q u e n c y ^ f ^ e x e r ^ d s e _ s e s s i o n s , a t t r i t i o n r a t e , p s y c h o l o g i c a l measure, composition of sample, gender, and study type were coded as independent v a r i a b l e s . E f f e c t s i z e was the dependent v a r i a b l e . A n a l y s i s of v a r i a n c e r e v e a l e d t h a t i-—• .. e x e r c i s e was an e f f e c t i v e s t r e s s reducer, s t r e s s e d people ... gained a g r e a t e r s t r e s s r e d u c t i o n e f f e c t than m i n i m a l l y s t r e s s e d peop_le, and t h e r e were no d i f f e r e n c e s between t r a i t a n d^state anxiety_.r.edu.c.t.ipn from p r e - to p o s t - e x e r c i s e program. In a d d i t i o n , a one-way ANOVA i n d i c a t e d t h a t t h e r e was a s i g n i f i c a n t d i f f e r e n c e between program l e n g t h s . Examination of the means r e v e a l e d t h a t an 8- to 12-week program was most ^ — — — • . e f f e c t i v e i n r e d u c i n g s t r e s s . Although t h e r e was a g r e a t e r e f f e c t s i z e for. unpublished s t u d i e s than p u b l i s h e d s t u d i e s , the p a t t e r n of change f o r each study type was s i m i l a r . The s i g n i f i c a n c e of these r e s u l t s and recommendations f o r f u t u r e s t u d i e s are d i s c u s s e d . i v T a b l e o f C o n t e n t s A b s t r a c t i i L i s t o f T a b l e s v i i L i s t o f F i g u r e s v i i i A c k n o w l e d g e m e n t s i x I n t r o d u c t i o n 1 P s y c h o l o g i c a l E f f e c t s o f E x e r c i s e . . . 2 E f f e c t s o f E x e r c i s e on S t r e s s 6 L i t e r a t u r e R e v i e w 11 S t r e s s a n d E x e r c i s e 11 D e f i n i t i o n o f S t r e s s 14 D e f i n i t i o n o f E x e r c i s e 16 E f f e c t s o f S i n g l e B o u t s o f E x e r c i s e 18 E f f e c t s o f an E x e r c i s e P r o g r a m 21 E f f e c t s o f e x e r c i s e p r o g r a m on t h e m i n i m a l l y s t r e s s e d 22 E f f e c t s o f e x e r c i s e p r o g r a m on t h e s t r e s s e d . . 26 F i t / u n f i t p e o p l e ' s r e a c t i o n t o s t r e s s o r s . . . 32 Summary 35 M e t a - a n a l y s i s • 35 B r i e f H i s t o r y o f M e t a - a n a l y s i s 37 A d v a n t a g e s o f M e t a - a n a l y s i s . . . . 39 L i m i t a t i o n s o f M e t a - a n a l y s i s 40 Summary . 44 M e t h o d 46 L i t e r a t u r e S e a r c h 4 6 V Design and Procedures 47 Study type 4 8 Design 48 Gender / 4 8 Composition of sample . 4 8 Stress l e v e l 48 P s y c h o l o g i c a l measure 49 Program length 4 9 Type of e x e r c i s e treatment 4 9 Frequency of e x e r c i s e session . 49 Leaders 49 A t t r i t i o n r a t e 50 Follow-up 50 C a l c u l a t i o n of E f f e c t Sizes . 51 Within group change 51 Contrast change 52 Data A n a l y s i s 54 Re s u l t s 56 S e l e c t i o n of Independent V a r i a b l e s f o r ANOVAS . . . 56 Treatment E f f e c t s . . . . . 56' Design 5 6 Stress l e v e l 59 Study type 64 Other V a r i a b l e s 66 D i s c u s s i o n • 68 Recommendations 74 v i R e f e r e n c e s 76 A p p e n d i x A 85 L i s t o f t h e 24 s t u d i e s i n c l u d e d i n t h e m e t a - a n a l y s i s 85 v i i L i s t o f T a b l e s 1. P r o c e d u r a l s t e p s i n m e t a - a n a l y s i s 41 2 . The mean a n d s t a n d a r d d e v i a t i o n o f e f f e c t s i z e s o f . i n d e p e n d e n t v a r i a b l e s 57 v i i i L i s t o f F i g u r e s 1. E f f e c t s i z e means f o r s t r e s s l e v e l b y p r o g r a m l e n g t h . 61 2. E f f e c t s i z e means o f s t a t e a n x i e t y f o r s t r e s s l e v e l b y p r o g r a m l e n g t h 63 3. E f f e c t s i z e means o f t r a i t a n x i e t y f o r s t r e s s l e v e l by p r o g r a m l e n g t h . 63 4. E f f e c t s i z e means f o r p r o g r a m l e n g t h b y s t u d y t y p e . . . 65 5. E f f e c t s i z e means f o r s t r e s s l e v e l by s t u d y t y p e 65 i x A c k n o w l e d g e m e n t s I am e t e r n a l l y g r a t e f u l t o P a u l C a l d e r h e a d , d e a r f r i e n d s a n d r e s e a r c h s u p e r v i s o r whose s u p p o r t a n d e n c o u r a g e m e n t i n my d a r k e s t h o u r s made i t p o s s i b l e f o r me t o c o n t i n u e my t h e s i s . T h i s s t u d y w o u l d n o t h a v e b e e n p o s s i b l e w i t h o u t t h e g u i d a n c e a n d i n c r e d i b l e p a t i e n c e o f D r . B o n i t a L o n g . I w o u l d l i k e t o e x p r e s s a p p r e c i a t i o n t o D r . L o n g , r e s e a r c h s u p e r v i s o r , f o r , s h a r i n g h e r e x t e n s i v e k n o w l e d g e o f t h e s t r e s s c o n c e p t a n d e x e r c i s e , f o r h e r s u p p o r t a n d h e l p f u l s u g g e s t i o n s t h r o u g h o u t my t h e s i s . I w o u l d a l s o l i k e t o t h a n k D r . R. S c h u t z f o r h i s g e n e r o u s d o n a t i o n o f t i m e t o d i s c u s s t h e m e t h o d o l o g y , a n d s t a t i s t i c a l m a t t e r s . H i s p a t i e n t g u i d a n c e was i n v a l u a b l e i n c l a r i f y i n g t h e m e t a - a n a l y t i c a p p r o a c h a n d s t a t i s t i c a l a n a l y s i s . I w o u l d a l s o l i k e t o t h a n k D r . K. C o u t t s f o r h i s s u p p o r t a n d comments on my t h e s i s . My a c k n o w l e g e m e n t w o u l d n o t be c o m p l e t e w i t h o u t a warm t h a n k - y o u t o S a s h a whose s m i l e a n d a n t i c s h e l p e d t o b r i n g l a u g h t e r i n t o my most s t r e s s f u l t i m e s . I n t r o d u c t i o n In the l a s t decade, e x e r c i s e as a p r e s c r i p t i o n f o r improved p h y s i c a l and p s y c h o l o g i c a l h e a l t h , i n p a r t i c u l a r s t r e s s , has r e c e i v e d i n c r e a s i n g a t t e n t i o n i n the h e a l t h f i e l d (Berger, Friedmann, & Eaton, 1988; Goldwater & C o l l i s , 1985; Hughes, Casa l , & Leon, 1986; Morgan, 1985). The p s y c h o l o g i c a l b e n e f i t s of e x e r c i s e are widely espoused i n popular h e a l t h , f i t n e s s , and p s y c h o l o g i c a l l i t e r a t u r e ( F o l k i n s & Sime, 1981; • Morgan & Goldston, 1987; Sachs, 1982). Although the mechanisms i n v o l v e d i n the p h y j ^ j D l o j g i c ^ a ^ have been w e l l documented (Barnard & Anthony, 1980; Bjurstrom & ^ — . ^ • . A l e x i o u s , 1978; Nelson, Jennings, E s l e r , & Korner, 1986), the p s y c h o l o g i c a l b e n e f i t s and u n d e r l y i n g change processes have not been as c l e a r l y d e l i n e a t e d (for reviews see F o l k i n s & Sime, 1981; Hughes, 1984; Ledwidge, 1980; Mihevic, 1982) . Research on the p s y c h o l o g i c a l b e n e f i t s of e x e r c i s e has shown c o n f l i c t i n g outcomes (Berger & Owen, 1987; Blumenthal, W i l l i a m s , Needels, & Wallace, 1982; Hughes, 1984; Nagy & F r a z i e r , 1988; Setaro, 1985). Thus the e f f i c a c y of e x e r c i s e as a treatment modality f o r s t r e s s i s u n c e r t a i n . Because t r a d i t i o n a l reviews i n t h i s area have f a i l e d to s y s t e m a t i c a l l y and q u a n t i t a t i v e l y analyze the research i n order to e s t a b l i s h g e n e r a l i z a t i o n s concerning e x e r c i s e and s t r e s s , the purpose of t h i s study i s t o i n t e g r a t e research on e x e r c i s e as a treatment f o r s t r e s s through meta-analysis. The analyses w i l l attempt to answer the £oXlow-i-ng- -Questions-:—I.s_exer.cise an e f f e c t i v e •J treatment f o r s t r e s s reduction? Is e x e r c i s e more e f f e c t i v e i n t r e a t i n g people who report j g r e a t e r s t r e s s l e v e l s than people with 1 eSB__str^ss_?_ What_t.y.p.e_ of exercise, i s the most ef fe_ctive s t r e s s reducer? P s y c h o l o g i c a l E f f e c t s of Ex e r c i s e An e a r l y review by Ledwidge .(1980) focused mainly on proposed hypotheses f o r the e f f e c t s of aerobic e x e r c i s e on mood s t a t e s . He d i d not review and i n t e g r a t e the r e s u l t s of st u d i e s i n order to deduce whether e x e r c i s e had a p o s i t i v e e f f e c t on mood. His paper was l a r g e l y concerned w i t h the hypothesis of the study. From h i s review, he concluded t h a t e x e r c i s e did_have a posit.iy.e e^fec^orwaood. However, because the purpose of t h i s study i s to review outcomes, Ledwidge's review w i l l not be described i n d e t a i l . A major review by F o l k i n s and Sime (1981) focused on cr - 1 theory and research that r e l a t e d e x e r c i s e to improvements i n p s y c h o l o g i c a l e v a r i a b l e s such as mood, s e l f - c o n c e p t , and work performance among normal as w e l l as s e l e c t e d c l i n i c a l p o p u l a t i o n s . They i d e n t i f i e d the design problems, v a r i a t i o n s i n e x e r c i s e , and the use of a wide range of p s y c h o l o g i c a l v a r i a b l e s that made r e s u l t s d i f f i c u l t t o i n t e r p r e t . In a d d i t i o n they found that much of the research r e l a t i n g e x e r c i s e programs to a f f e c t focused on the s t r e s s emotions, e s p e c i a l l y a n x i e t y . Most of the st u d i e s reviewed showed th a t f i t n e s s was a s s o c i a t e d with improvements i n mood s t a t e s . This e f f e c t was more pronounced_w.ith_participants who were d i s t r e s s e d o r p h y s i c a l . l y _ . _ u n.f.i.t _a . t_ t he_o.ut.s.e_t_.__ How e v e r , o n l y one o f t h o s e s t u d i e s was a t r u e e x p e r i m e n t a l d e s i g n . T h e y a l s o f o u n d t h a t e x e r c i s e t r a i n i n g i n t e r v e n t i o n s were f r e q u e n t l y o f f e r e d t o i n d i v i d u a l s who were i n t e r e s t e d i n p a r t i c i p a t i n g i n an e x e r c i s e p r o g r a m . T h i s s e l e c t i o n b i a s i s a t h r e a t t o t h e v a l i d i t y o f t h e s e s t u d i e s a n d c o n f o u n d s c o m p a r i s o n s w i t h c o n t r o l g r o u p s . W i t h r e g a r d t o p e r s o n a l i t y , F o l k i n s a n d S ime (1981) f o u n d t h a t s e l f - c o n c e p t was most c o n s i s t e n t l y a s s o c i a t e d w i t h improvemejit^s__jm.__pJ^^ T h e r e was a l s o e v i d e n c e o f t h e p o s i t i v e e f f e c t s o f e x e r c i s e on c o g n i t i v e f u n c t i o n . E x e r c i s e a p p e a r e d t o b o l s t e r c o g n i t i v e p e r f o r m a n c e ( e . g . , p e r f o r m a n c e o f m e n t a l t a s k s ) d u r i n g a n d a f t e r p h y s i c a l a c t i v i t y . F o l k i n s a n d Sime a l s o e x a m i n e d t h e o r e t i c a l p e r s p e c t i v e s w h i c h c o u l d o f f e r e x p l a n a t i o n s f o r t h e e f f e c t o f e x e r c i s e s on p s y c h o l o g i c a l f u n c t i o n i n g . T h e y e x p l o r e d s o m a t o p s y c h i c t h e o r i e s , p s y c h o l o g i c a l v i e w p o i n t s a n d a c o g n i t i v e l y o r i e n t a t e d m o d e l . The l a t t e r was t h e most s a t i s f a c t o r y i n t h e i r o p i n i o n . t h e f i t n e s s t r a i n i n g e f f e c t may be v i e w e d a s a s e l f - r e g u l a t i o n ( c o p i n g ) p r o c e s s t h a t e n h a n c e s a d a p t i v e i n t e r a c t i o n s w i t h a p e r s o n ' s e n v i r o n m e n t " (p . 3 7 4 ) . In L a z a r u s a n d F o l k m a n ' s (1984) s t r e s s a n d c o p i n g t h e o r y , c o p i n g b e h a v i o u r i s a n t e c e d e n t t o e m o t i o n a l r e a c t i o n s a n d r e g u l a t e s i t s f o r m a n d i n t e n s i t y . T h u s e x e r c i s e may be c o n s i d e r e d a s e l f - r e g u l a t o r y s t r a t e g y i n a d a p t i n g t o s t r e s s f u l s i t u a t i o n s . Since F o l k i n s and Sime's review there has been an improvement i n some of the study designs (e.g., c o n t r o l groups, measuring f i t n e s s l e v e l s pre- to p o s t - t e s t ) and attempts to examine the e f f e c t s of e x e r c i s e on p a r t i c u l a r p s y c h o l o g i c a l v a r i a b l e s (e.g., Roskies et a l . , 1986). Further examples of improvements i n study designs are mentioned i n the l i t e r a t u r e review. In a more s p e c i f i c review, Mihevic (1982) examined the e f f e c t s of acute and chronic e x e r c i s e on anxiety and the e f f e c t s of chronic "exercise on depression. He concluded t h a t vigorous, s i n g l e bouts of e x e r c i s e were a s s o c i a t e d with reductions i n s t a t e anxiety o r " t e n s i o n . Both normal and anxious i n d i v i d u a l s d i s p l a y e d a red u c t i o n i n an x i e t y 20-30 minutes post e x e r c i s e . However, there were only a few experimental s t u d i e s of the chronic e f f e c t s of e x e r c i s e on. s t a t e a n x i e t y . There was some evidence t h a t chronic running decreased muscular t e n s i o n and s e l f - r e p o r t e d s t a t e a n x i e t y f o r male p a r t i c i p a n t s . The studie s a l s o showed th a t a vigorous e x e r c i s e program was a s s o c i a t e d with decreases i n depression f o r people who were c l i n i c a l l y depressed. The l a t t e r p a r t of h i s review examined b i o c h e m i c a l / p h y s i o l o g i c a l explanations or hypotheses f o r the e f f e c t s of e x e r c i s e on a f f e c t i v e s t a t e s . He i d e n t i f i e d processes such as l a c t a t e metabolism and endorphins as f a c t o r s that may mediate the e f f e c t s of e x e r c i s e on -anxiety. Mihevic d i d not e x p l a i n how he d e r i v e d h i s conclusions or what c r i t e r i a f o r i n c l u s i o n was used f o r the a r t i c l e s reviewed. He d i d however mention th a t l i t t l e i n f o r m a t i o n was provided about the f i t n e s s l e v e l s of p a r t i c i p a n t s and the changes i n f i t n e s s l e v e l s a f t e r an e x e r c i s e program. Hughes' (1984) i n t e g r a t i v e review of c o n t r o l l e d experiments examined the r e l a t i o n s h i p of h a b i t u a l aerobic e x e r c i s e and mood, p e r s o n a l i t y , and c o g n i t i o n . This review, l i k e F o l k i n s and Sime's (1981) review, d i d not use a q u a n t i t a t i v e a n a l y s i s to e s t a b l i s h g e n e r a l i z a t i o n s about the issues under examination, nor d i d i t document a systematic a n a l y s i s of the research being reviewed. The conclusions were that e x e r c i s e improved s e l f - c o n c e p t , however there was l i t t l e evidence f o r claims that e x e r c i s e improved an x i e t y , depression, body image, p e r s o n a l i t y , or c o g n i t i o n . Hughes noted that there were over 1,000 a r t i c l e s w r i t t e n on the p s y c h o l o g i c a l e f f e c t s of e x e r c i s e as w e l l as s e v e r a l reviews of the e f f e c t s of e x e r c i s e on anxiety, depression, p e r s o n a l i t y , c o g n i t i o n , and work performance. Hughes suggested th a t " f u t u r e research should examine the i n d i v i d u a l s and the d i s o r d e r s t h a t are most l i k e l y to experience p s y c h o l o g i c a l b e n e f i t s from e x e r c i s e , the types of e x e r c i s e that are most b e n e f i c i a l , and the proposed mechanisms f o r the p s y c h o l o g i c a l b e n e f i t s " (p. 66). In summary, researchers have been studying the e f f e c t s of e x e r c i s e on a wide range of p s y c h o l o g i c a l v a r i a b l e s , i n c l u d i n g s t r e s s , without a r r i v i n g at d e f i n i t i v e conclusions regarding the b e n e f i c i a l influence of exercise on mood or stress (Abood, 198-4r~"B"lumenthal et a l . , 1982/ Dorinsky, 1984/ Hughes et a l . , 1986). , • Although Ledwidge (1980) and Folkins and Sime (1981) agree that exercise i s associated with improvements i n mood states, Folkins and Sime (1981) also considered exercise to be a self-regulatory strategy i n adapting to s t r e s s f u l s i t u a t i o n s . Thfs~view supports MihevicT's (T9"8~2~)""cbricTusion that acute and chronic exercise decreased state anxiety and muscular tension. Hughes (1984) disagreed with the above reviewers and noted that there was l i t t l e evidence for the claims that exercise improved mood or anxiety. E f f e c t s of Exercise on Stress The burgeoning of stress research r e s u l t s from a growing concern for the health of the population on the part of governments and organizations (Cox, Gotts, Boot, & Kerr, 1988). This has been shown by the increase in stress management and health promotion programs within the workplace and other communities. Physical f i t n e s s programs are common components of stress management and health promotion i n the workplace ( P e l l e t i e r , 1986). Although the effectiveness of exercise programs as a treatment for stress and psychological health i s not well supported with s c i e n t i f i c research, the rationale for i t s effectiveness exists due to personal experiences (Cooper, 1978/ Sheehan, 1978) and l i m i t e d research support (Long, 1984/ Long & Haney, 1988). 7 A f r e q u e n t l y reported observation of researchers, c l i n i c i a n s , and l a y people i s that many i n d i v i d u a l s experience an enhanced f e e l i n g of w e l l - b e i n g f o l l o w i n g p h y s i c a l a c t i v i t y (Dorinsky, 1984; M e l l i o n , 1985; Sachs & Buffone, 1984; Sheehan, 1978). These observations have provided the b a s i s f o r the p r e s c r i p t i o n of e x e r c i s e f o r s t r e s s r e d u c t i o n (Byrd, 1963; de V r i e s , 1968; de V r i e s & Adams, 1972; Dorinsky, 1984). However research on e f f e c t s of e x e r c i s e on s t r e s s i s v a r i e d i n design, d e f i n i t i o n s of e x e r c i s e and s t r e s s , and the degree to which the p a r t i c i p a n t s are s t r e s s e d p r i o r t o i n t e r v e n t i o n . The f i n d i n g s from s e v e r a l s t u d i e s suggest t h a t e x e r c i s e of an endurance nature reduces anxiety i n s t r e s s e d a d u l t s (Dorinsky, 1984; Long, 1984; Long & Haney, 1988; Steptoe, Edwards, Moses, & Mathews, 1989; Wilson, 1985). These s t u d i e s p r e s c r i b e d e x e r c i s e 3 times per week f o r an average of 8-weeks. The e x e r c i s e programs were found to be as e f f e c t i v e as other stress-management i n t e r v e n t i o n s ( i . e . , p r o g r e s s i v e r e l a x a t i o n and s t r e s s - i n o c u l a t i o n t r a i n i n g ) . There are other data to suggest that e x e r c i s e has p o s i t i v e e f f e c t s on t r a i t a n x i e t y and/or mood (tension) i n p a r t i c i p a n t s (students and adult volunteers) who are not p a r t i c u l a r l y s t r e s s e d (Abood, 1984; Berger et a l . , 1988; Eby, 1985; Moses, Steptoe, Mathews, & Edwards, 1989). Studies that examined recovery from s t r e s s f u l s i t u a t i o n s , comparing f i t and u n f i t groups, have found that the f i t groups p h y s i o l o g i c a l l y ( i . e . , pulse and blood pressure) recover more 8 r a p i d l y (Holmes & Roth, 1985; M c G i l l e y & Holmes, 1988). However, there was l i t t l e d i f f e r e n c e between the f i t / u n f i t p a r t i c i p a n t s posttreatment p s y c h o l o g i c a l measure ( i . e . , a qu e s t i o n n a i r e t e s t i n g s u b j e c t i v e a r o u s a l ; Holmes, 1982) . The p a r t i c i p a n t s were subjected to s t r e s s f u l c o g n i t i v e t e s t s and i t was found t h a t the f i t groups i n d i c a t e d smaller c a r d i o v a s c u l a r (blood pressure and heart rate) and some s u b j e c t i v e responses (anxiety measure) to p s y c h o l o g i c a l s t r e s s . Moreover, Morgan (1979) and de V r i e s (1968) and t h e i r a s s o c i a t e s have c o n s i s t e n t l y demonstrated th a t acute e x e r c i s e •reduces s t a t e anxiety and muscle t e n s i o n . Thus some research showed a decrease i n s t r e s s with e x e r c i s e as a treatment modality, whereas other research showed no s i g n i f i c a n t e f f e c t s regarding the e f f i c a c y of e x e r c i s e as a treatment f o r s t r e s s (Nagy & F r a z i e r , 1988; Setaro, 1985; Stern & Cleary, 1982). In a d d i t i o n , research on e x e r c i s e as a s t r e s s treatment had design l i m i t a t i o n s and used a wide range of p s y c h o l o g i c a l v a r i a b l e s , thus r e s u l t s are oft e n d i f f i c u l t to i n t e r p r e t . Furthermore, these s t u d i e s f r e q u e n t l y t a r g e t e d a pop u l a t i o n that was not p a r t i c u l a r l y s t r e s s e d or anxious (Bahrke & Morgan, 1978; Berger & Owen, 1987). In s p i t e of the c o n t r a d i c t o r y f i n d i n g s there i s a strong b e l i e f that e x e r c i s e has a p o s i t i v e e f f e c t on s t r e s s (Sachs & Buffone, 1984). Therefore i t i s important that t h i s b e l i e f be corroborated by a q u a n t i t a t i v e , i n t e g r a t i v e review of research on t h i s phenomena. 9 In o r d e r t o a n s w e r t h e q u e s t i o n i s e x e r c i s e an e f f e c t i v e t r e a t m e n t f o r s t r e s s , r e v i e w s o f t h e r e s e a r c h c o n d u c t e d t o d a t e h a v e b e e n i n c o n c l u s i v e . H o w e v e r , t h e s e r e v i e w s h a v e h a d s e v e r a l l i m i t a t i o n s : (a) T h e y h a v e m a i n l y e x a m i n e d p u b l i s h e d r e s e a r c h . (b) T h e y h a v e n o t b e e n q u a n t i t a t i v e l y r i g o r o u s a n d d i d n o t d o c u m e n t t h e i r m e t h o d o l g y ao t h a t t h e i r r e v i e w c o u l d be r e p l i c a b l e . (c) T h e y h a v e n o t e x a m i n e d o u t c o m e r e s e a r c h — c o m p a r i n g t r e a t m e n t p a c k a g e s f o r s t r e s s / a n x i e t y . (d) T h e y e x a m i n e d t h e p r o p o s e d m e c h a n i s m s t h a t m e d i a t e b e t w e e n t h e e x e r c i s e a n d t h e p s y c h o l o g i c a l b e n e f i t s w i t h o u t any " p r o o f " o f t h e a s s u m p t i o n s b e i n g m a d e . In o r d e r t o combat some o f t h e p r e v i o u s l i m i t a t i o n s , t h i s s t u d y i n c o r p o r a t e s a m e t a - a n a l y t i c a p p r o a c h , w h i c h i n t e g r a t e s r e s e a r c h t h a t e x a m i n e d t h e e f f e c t i v e n e s s o f e x e r c i s e a s a t r e a t m e n t f o r s t r e s s . M e t a - a n a l y s i s i s d e f i n e d a s " t h e s t a t i s t i c a l a n a l y s i s o f summary f i n d i n g s o f many e m p i r i c a l s t u d i e s " ( G l a s s , McGaw, & S m i t h , 1 9 8 1 , p . 2 1 ) . M e t a - a n a l y s i s c a n p r o v i d e a q u a n t i t a t i v e a n a l y s i s i n o r d e r t o a n s w e r s p e c i f i c q u e s t i o n s r e g a r d i n g t h e e f f i c a c y o f e x e r c i s e a s a t r e a t m e n t f o r s t r e s s e d i n d i v i d u a l s . The v a r i a b l e s ( e . g . , t y p e o f e x e r c i s e , t r e a t m e n t l e n g t h , t y p e o f l e a d e r s h i p f o r t r e a t m e n t , s t r e s s l e v e l , d e s i g n t y p e , p u b l i c a t i o n ) t h a t i n f l u e n c e t h e o u t c o m e o f s t u d i e s a r e e x a m i n e d i n o r d e r t o a n s w e r s p e c i f i c q u e s t i o n s r e g a r d i n g t h e e f f e c t s o f e x e r c i s e s t r e s s . T h e f o l l o w i n g q u e s t i o n s were p o s e d : I s e x e r c i s e an e f f e c t i v e t r e a t m e n t f o r s t r e s s r e d u c t i o n ? I s e x e r c i s e more e f f e c t i v e i n t r e a t i n g p e o p l e who r e p o r t g r e a t e r s t r e s s l e v e l t h a n p e o p l e w i t h l e s s s t r e s s ? What t y p e o f e x e r c i s e i s t h e m o s t e f f e c t i v e s t r e s s r e d u c e r ? L i t e r a t u r e Review Stress and E x e r c i s e Today most people b e l i e v e that e x e r c i s e has p o s i t i v e e f f e c t s on a l l aspects of h e a l t h . In the l a s t decade, e x e r c i s e as a p r e s c r i p t i o n f o r improved p h y s i c a l and p s y c h o l o g i c a l h e a l t h , i n p a r t i c u l a r s t r e s s , has r e c e i v e d i n c r e a s i n g a t t e n t i o n i n the h e a l t h f i e l d (Berger et a l . , 1988; Goldwater & C o l l i s , 1985; Hughes et a l . , 1986; Morgan, 1985). The N a t i o n a l I n s t i t u t e of Mental Health formulated the f o l l o w i n g consensus statements: P h y s i c a l f i t n e s s i s p o s i t i v e l y a s s o c i a t e d w i t h mental h e a l t h and w e l l - b e i n g . E x e r c i s e i s a s s o c i a t e d with the r e d u c t i o n of s t r e s s emotions such as s t a t e a n x i e t y . Long-term e x e r c i s e i s u s u a l l y a s s o c i a t e d with reductions i n t r a i t s such as n e u r o t i c i s m and a n x i e t y . Appropriate e x e r c i s e r e s u l t s i n reductions i n v a r i o u s s t r e s s i n d i c e s such as neuromuscular t e n s i o n , r e s t i n g heart r a t e , and some s t r e s s hormones. Current c l i n i c a l o p i n i o n holds that e x e r c i s e has b e n e f i c i a l emotional e f f e c t s across a l l ages and i n both sexes (Morgan, 1985, p. 95) . These statements assume that research has c o n c l u s i v e l y v e r i f i e d t h a t e x e r c i s e i s an e f f e c t i v e s t r e s s management technique. Yet t h i s i s not so because the research outcomes are v a r i e d . There i s l i t t l e consistency i n research designs, length of treatment, type and i n t e n s i t y of e x e r c i s e , and p o p u l a t i o n and anxiety type among the s t u d i e s . 12 pop u l a t i o n and anxiety type among the s t u d i e s . The demands of our ever changing world prevent few to escape the s t r e s s e s and s t r a i n s of d a i l y l i v i n g (Abood, 1984; Berger & Owen, 1987). P r o f e s s i o n a l s are p r e s c r i b i n g e x e r c i s e f o r p h y s i o l o g i c a l and p s y c h o l o g i c a l problems (Hales & T r a v i s , 1987). Although the mechanisms i n v o l v e d i n the p h y s i o l o g i c a l b e n e f i t s of e x e r c i s e have been w e l l documented (Barnard & Anthony, 1980; Bjurstrom & A l e x i o u s , 1978; Nelson, Jennings, E s l e r , & Korner, 1986) , the p s y c h o l o g i c a l b e n e f i t s and und e r l y i n g change processes have not been as c l e a r l y d e l i n e a t e d (for reviews see F o l k i n s & Sime, 1981; Hughes, 1984; Ledwidge, 1980; Mihevic, 1982). This s t r e s s f u l era has seen a growing concern f o r the h e a l t h of the pop u l a t i o n on the part of governments and employment o r g a n i z a t i o n s (Cox et al.', 1988) . As a r e s u l t , there i s an increase i n s t r e s s management and h e a l t h promotion programs w i t h i n the workplace and other communities. P h y s i c a l f i t n e s s programs are common components of s t r e s s management and h e a l t h promotion i n the workplace ( P e l l e t i e r , 1986). However the e f f e c t i v e n e s s of e x e r c i s e programs as a treatment f o r s t r e s s and p s y c h o l o g i c a l h e a l t h i s not w e l l supported. The r a t i o n a l e f o r i t s e f f e c t i v e n e s s i s provided mainly by anecdotal s t u d i e s (Sachs & Buffone, 1984) and some research support (Long, 1984; Wilson, 1985) . Yet the p s y c h o l o g i c a l b e n e f i t s of e x e r c i s e continue to be widely espoused i n popular h e a l t h , f i t n e s s , and p s y c h o l o g i c a l l i t e r a t u r e ( F o l k i n s & Sime, 1981; Morgan & Goldston, 1987; Sachs, 1982) . S t r a s s e r (1989) s t a t e s t h a t "Exercise p r e s c r i p t i o n s are now commonplace. P s y c h i a t r i s t s p r e s c r i b e e x e r c i s e to reduce nervous t e n s i o n ; . . . . E x e r c i s e , however, does make people f e e l b e t t e r , and thus has a p o s i t i v e e f f e c t on h e a l t h . This helps counter the i n c r e a s i n g i n f l u e n c e of s t r e s s As a countermeasure, business has s t a r t e d s t r e s s - r e d u c i n g programs using e x e r c i s e programs" (p. 110). These statements appear i n an occupational h e a l t h and s a f e t y j o u r n a l as i r r e f u t a b l e f a c t . Given the need to f i n d a v a r i e t y of e f f e c t i v e coping s t r a t e g i e s f o r the st r e s s e s and s t r a i n s of d a i l y l i v i n g , c l i n i c i a n s are p r e s c r i b i n g e x e r c i s e as a v i a b l e coping s t r a t e g y . However research has not produced d e f i n i t i v e answers regarding the e f f e c t of e x e r c i s e on s t r e s s and anxie t y mood s t a t e s . Studies to date have had va r y i n g r e s u l t s i n examining the r e l a t i o n s h i p of e x e r c i s e and s t r e s s . There are many methodological l i m i t a t i o n s i n the st u d i e s w i t h i n t h i s area. The s t u d i e s vary i n terms of research designs and approaches as w e l l as using a v a r i e t y of paper-and-pencil instruments f o r anxie t y . Therefore, there i s a need t o f i n d answers t o some b a s i c questions common to most of these s t u d i e s . A method of i n t e g r a t i n g t h i s i n f o r m a t i o n and answering some common research questions i s meta-analysis. Before e l a b o r a t i n g on the meta-analytic approach, a d e f i n i t i o n of s t r e s s and e x e r c i s e and the types of st u d i e s a v a i l a b l e i n t h i s area must be d e l i n e a t e d . T h e r e a r e f i v e k e y c a t e g o r i e s i n t o w h i c h t h e s t u d i e s c a n be a s s i g n e d : t h e e f f e c t s o f s i n g l e b o u t s o f e x e r c i s e on s t a t e a n x i e t y , t h e e f f e c t s o f an e x e r c i s e p r o g r a m on p e o p l e ' s mood , t h e e f f e c t s o f an e x e r c i s e p r o g r a m on p e o p l e who were n o t p a r t i c u l a r l y s t r e s s e d , t h e e f f e c t s o f an e x e r c i s e p r o g r a m on p e o p l e who were s t r e s s e d , a n d t h e p h y s i o l o g i c a l a n d p s y c h o l o g i c a l r e p s o n s e s o f f i t a n d u n f i t p e o p l e t o s t r e s s o r s . D e f i n i t i o n o f S t r e s s The w o r d s s t r e s s a n d a n x i e t y a r e o f t e n u s e d i n t e r c h a n g e a b l y i n r e s e a r c h on s t r e s s o r a n x i e t y ( S p i e l b e r g e r , 1 9 7 2 ) . S t r e s s w i t h i n t h e c o n t e x t o f t h i s r e v i e w i s c o n s i d e r e d t o be a t r a n s a c t i o n a l , p r o c e s s - o r i e n t e d p h e n o m e n a ( L a z a r u s & F o l k m a n , 1 9 8 4 ) . L a z a r u s ' t r a n s a c t i o n a l v i e w o f s t r e s s i s a h o l i s t i c p e r s p e c t i v e a n d t a k e s i n t o a c c o u n t t h e p a r t i c u l a r l i f e e x p e r i e n c e s o f t h e i n d i v i d u a l , t h e i r p e r s o n a l v a l u e s y s t e m a n d t h e e n v i r o n m e n t a l f a c t o r s i n t e r a c t i n g t o g e t h e r t o c r e a t e a s p e c i f i c a p p r a i s a l o f a s p e c i f i c e v e n t . In t h i s m o d e l , a n x i e t y i s one o f many e m o t i o n s w h i c h may r e s u l t due t o t h e p e r c e p t i o n o f t h r e a t w i t h i n t h e s i t u a t i o n . T h i s m o d e l i s u s e f u l b e c a u s e i t p u r p o r t s t h a t t h e e x p e r i e n c e o f s t r e s s i s a s u b j e c t i v e p e r c e p t i o n o f a s i t u a t i o n . T h u s s t r e s s may be a s s e s s e d w i t h s e l f - r e p o r t m e a s u r e s o f e m o t i o n s s u c h a s a n x i e t y a n d t e n s i o n . Two m a i n f e a t u r e s o f L a z a r u s a n d F o l k m a n ' s (1984) t h e o r y i n c l u d e s t h e i n d i v i d u a l ' s a s s e s s m e n t p r o c e s s o f p r i m a r y a p p r a i s a l (what i s t h e s i g n i f i c a n c e o f t h i s s i t u a t i o n t o t h e d o n e a b o u t t h i s s i t u a t i o n now o r l a t e r ? ) . S h o u l d t h e s i t u a t i o n be a s s e s s e d a s b e i n g a t h r e a t , a l o s s / h a r m , o r a c h a l l e n g e t o t h e p e r s o n ; e m o t i o n s s u c h a s f e a r , a n x i e t y , d e p r e s s i o n o r a n g e r may b e e v o k e d , w h e r e a s t h e e m o t i o n s e v o k e d b y c h a l l e n g e a r e a p t t o b e more h o p e f u l o f a s u c c e s s f u l o u t c o m e . The i n d i v i d u a l ' s r e s p o n s e t o t h e p r i m a r y a p p r a i s a l may f a v o u r an e m o t i o n - f o c u s e d a n d / o r p r o b l e m - f o c u s e d c o p i n g s t y l e . E m o t i o n - f o c u s e d c o p i n g i s o r i e n t e d t o w a r d r e g u l a t i o n o f e m o t i o n s a n d p r o b l e m - f o c u s e d c o p i n g i s o r i e n t e d t o w a r d d o i n g s o m e t h i n g t o r e l i e v e t h e p r o b l e m ( L a z a r u s & F o l k m a n , 1 9 8 4 ) . E x e r c i s e i n t h i s s t u d y i s a s s u m e d t o be u s e d b y t h e i n d i v i d u a l i n s e v e r a l w a y s . I t may be a m e t h o d o f c o p i n g w i t h t h e s t r e s s / a n x i e t y e m o t i o n s e v o k e d by a s i t u a t i o n ; an e m o t i o n r e g u l a t o r ( i . e . , d e c r e a s e m u s c l e t e n s i o n , b r e a t h e d e e p l y ) . H o w e v e r i t c a n a l s o be u s e d a s a m e t h o d o f s o l v i n g a p r o b l e m ( i . e . , t h i n k i n g o f s o l u t i o n s w h i l e r u n n i n g , a t i m e - t o ^ c o o l down ' b e f o r e s p e a k i n g w i t h a n o t h e r a b o u t a c o n f l i c t u a l s i t u a t i o n ) ; . A n x i e t y i s an e m o t i o n a l s t a t e w h i c h c a n v a r y i n i n t e n s i t y a n d i s a r o u s e d b y t h e p e r s o n ' s p e r c e p t i o n o f a t h r e a t o r d a n g e r t o t h e s e l f ( S a r a s o n , 1 9 8 5 ) . T h i s t h r e a t o r d a n g e r d o e s n o t n e c e s s a r i l y r e f l e c t t h e o b j e c t i v e r e a l i t y b u t t h e p e r s o n ' s n o t i o n o f what i s d a n g e r o u s t o t h e s e l f . S p i e l b e r g e r (1972) d e f i n e d a n x i e t y a s " a n u n p l e a s a n t e m o t i o n a l s t a t e o r c o n d i t i o n w h i c h i s c h a r a c t e r i z e d b y s u b j e c t i v e f e e l i n g s o f t e n s i o n , a p p r e h e n s i o n , a n d w o r r y , a n d by s t a t e o r c o n d i t i o n w h i c h i s c h a r a c t e r i z e d b y s u b j e c t i v e f e e l i n g s o f t e n s i o n , a p p r e h e n s i o n , a n d w o r r y , a n d b y a c t i v a t i o n o r a r o u s a l o f t h e a u t o n o m i c n e r v o u s s y s t e m " (p . 4 8 2 ) . He a l s o r e f e r r e d t o s t a t e a n x i e t y a s t h e e m o t i o n a l r e a c t i o n s t h a t a r e e v o k e d i n p e o p l e when t h e y p e r c e i v e a s i t u a t i o n t o be t h r e a t e n i n g . T h e r e f o r e an a n x i e t y s t a t e e x i s t s a t a p a r t i c u l a r moment i n t i m e , a n d a t a c e r t a i n i n t e n s i t y d e p e n d i n g on t h e amount o f t h r e a t p e r c e i v e d . T r a i t a n x i e t y w o u l d r e f l e c t t h e r e l a t i v e l y e n d u r i n g i n d i v i d u a l t e n d e n c y t o a p p r a i s e s i t u a t i o n s a s t h r e a t e n i n g . T h e s e two p s y c h o l o g i c a l c o n s t r u c t s a r e m e a s u r e d i n S p i e l b e r g e r ' s S t a t e - T r a i t A n x i e t y I n v e n t o r y ( S p i e l b e r g e r , G o r s u c h , & L u s h e n e , 1 9 7 0 ) . T h e r e a r e o t h e r p a p e r - a n d - p e n e i l i n s t r u m e n t s w h i c h a l s o m e a s u r e e i t h e r s t a t e o r t r a i t a n x i e t y . T h e r e f o r e , i n t h i s s t u d y s t r e s s w i l l be o p e r a t i o n a l i z e d b y s e l f - r e p o r t e d m e a s u r e s o f a n x i e t y a n d t e n s i o n . G i v e n t h a t p e o p l e a r e t h e b e s t j u d g e s o f t h e i r e m o t i o n a l s t a t e a t a n y p a r t i c u l a r moment . T h u s s t u d i e s f o c u s e d on a l l l e v e l s o f a n x i o u s n e s s , w i t h t h e e x c e p t i o n o f a n x i e t y d i s o r d e r s (as d e f i n e d b y DSM 1 1 1 ; A m e r i c a n P s y c h i a t r i c A s s o c i a t i o n , 1980) t h a t w o u l d be t r e a t e d i n a p s y c h i a t r i c / c l i n i c a l s e t t i n g , a r e c o n s i d e r e d a p p r o p r i a t e f o r t h e s t u d y . D e f i n i t i o n o f E x e r c i s e E x e r c i s e i s v i e w e d a s any p h y s i c a l a c t i v i t y w h i c h t a x e s t h e p h y s i o l o g i c a l s y s t e m s o f t h e i n d i v i d u a l , a n d t h e c o n d i t i o n i n g e f f e c t d e s i r e d w i l l d i c t a t e t h e s p e c i f i c t y p e o f 17 a c t i v i t y ( F o x , B o w e r s , & F o s s , 1988) . T h e r e a r e u s u a l l y t h r e e a r e a s w h i c h i n d i v i d u a l s want t o i m p r o v e : m u s c u l a r s t r e n g t h a n d e n d u r a n c e , f l e x i b i l i t y , a n d c a r d i o v a s c u l a r e n d u r a n c e . The l a t t e r i s t h e m o s t commonly p r e s c r i b e d a s t r e a t m e n t f o r s t r e s s ( D o r i n s k y , 1984; S i n y o r e t a l . , 1983; T a y l o r e t a l . , 1985). C a r d i o v a s c u l a r e n d u r a n c e i s a c h i e v e d by t h e r h y t h m i c c o n t r a c t i o n s o f l a r g e m u s c l e g r o u p s o v e r a p e r i o d o f t i m e — a e r o b i c e x e r c i s e . A e r o b i c e x e r c i s e d e v e l o p s t h e a b i l i t y o f t h e r e s p i r a t o r y a n d c a r d i o v a s c u l a r s y s t e m s t o e f f i c i e n t l y d e l i v e r o x y g e n t o a l l t h e w o r k i n g m u s c l e s o v e r a p r o l o n g e d p e r i o d o f t i m e . F o r m s o f a e r o b i c e x e r c i s e a r e j o g g i n g / r u n n i n g , s w i m m i n g , b r i s k w a l k i n g , c r o s s c o u n t r y s k i i n g , r o w i n g , a n d c y c l i n g (Fox e t a l . , 1988). F I T T i s an a c r o n y m ' w h i c h i n d i c a t e s t h e b e s t way i n w h i c h t o a c h i e v e o p t i m u m a e r o b i c c o n d i t i o n i n g e f f e c t s ( S t e w a r t , 1982). F f r e q u e n c y o f e x e r c i s e - 3 t o 5 t i m e s p e r w e e k . I i n t e n s i t y o f e x e r c i s e - 60% t o 70% ( m o d e r a t e t o i n t e n s e r a n g e ) o f t h e p e r s o n ' s m a x i m a l h e a r t r a t e . T t i m e o f e x e r c i s e - i n i t i a l l y 15 m i n u t e s , w o r k i n g t o w a r d 30 m i n u t e s . T t y p e o f e x e r c i s e - e n d u r a n c e a c t i v i t i e s , w i t h . some s t r e n g t h a n d f l e x i b i l i t y . F I T T a l s o p r e s c r i b e s t h e o p t i m a l manner i n w h i c h t o g r a d u a l l y p r o c e e d i n any o t h e r t y p e o f e x e r c i s e p r o g r a m . A l t h o u g h many o f t h e s t u d i e s r e v i e w e d p r e s c r i b e d c a r d i o v a s c u l a r e n d u r a n c e e x e r c i s e a s t r e a t m e n t f o r s t r e s s , i n • 18 t h i s meta-analysis e x e r c i s e encompassed a more general d e f i n i t i o n . E x e r c i s e s t u d i e s were i n c l u d e d i f they contained any p h y s i c a l a c t i v i t y t h a t i n v o l v e d l a r g e muscle groups over a p e r i o d of at l e a s t 15 minutes f o r a minimum of 4 weeks. This would allow f o r the examination of whether a p a r t i c u l a r type of e x e r c i s e was (e.g., walking vs weight t r a i n i n g ) was best s u i t e d as a treatment f o r s t r e s s . E f f e c t s of S i n g l e Bouts of Ex e r c i s e E a r l i e r s t u d i e s examined the e f f e c t s of a s i n g l e dose of e x e r c i s e on s t a t e anxiety. Morgan (1973) described a s e r i e s of i n v e s t i g a t i o n s i n which he and colleagues explored the p o s s i b i l i t y t h a t vigorous p h y s i c a l a c t i v i t y c o uld be a u s e f u l "coping s t r a t e g y " f o r reducing anxiety. The p a r t i c i p a n t s were ca t e g o r i z e d as 'normal' or h i g h l y anxious depending on t h e i r score on the STAI p r i o r to p a r t i c i p a t i n g i n the e x e r c i s e . The f i n d i n g s revealed a s i g n i f i c a n t decrease i n s t a t e a n x i e t y between the p r e - e x e r c i s e and p o s t - e x e r c i s e t e s t on S t a t e - T r a i t Anxiety Inventory (STAI). Bahrke and Morgan (1978) compared the i n f l u e n c e of acute p h y s i c a l a c t i v i t y , m e d i t a t i o n , and a qu i e t r e s t session on anxiety. A s i g n i f i c a n t r e d u c t i o n i n anxiet y occurred f o r each treatment. Morgan hypothesized that because each treatment appeared t o be e f f e c t i v e , e x e r c i s e d i d not i n f l u e n c e s t a t e anxiety but an a c t i v i t y as a 'time-out' e f f e c t d i d . Morgan and Horstman (1976) conducted an experiment i n which two samples of 30 men walked to exhaustion on a motor d r i v e n t r e a d m i l l . The men used 80% of t h e i r maximum aerobic 19 power. State anxiety as measured by STAI before, during, and a f t e r the e x e r c i s e . Anxiety increased s i g n i f i c a n t l y i n e a r l y e x e r c i s e , reached a peak about h a l f way through, and then decreased r a p i d l y . The s t a t e anxiety l e v e l s had dropped below o r i g i n a l l e v e l s , 10 minutes a f t e r e x e r c i s e was completed. These r e s u l t s a p p l i e d to the the "normal" as w e l l as the c l i n i c a l l y anxious p a r t i c i p a n t s . Wood (1977) s t u d i e d the s t a t e a n x i e t y l e v e l s of 62 c o l l e g e males and 44 c o l l e g e females f o l l o w i n g a 12 minute run. There was a s i g n i f i c a n t decrease i n s t a t e a n x i e t y f o r the males and no s i g n i f i c a n t change f o r the females. He gives no expla n a t i o n f o r the gender d i f f e r e n c e s but he does d i s c u s s h i s f i n d i n g s i n terms of high and low anxious groups. He d i v i d e d the females and males i n t o high and low anxious groups and examined t h e i r a n x i e t y scores pre- to post-run. The high anxious group d i d reduce t h e i r s t a t e anxiety, whereas the low anxious group increased t h e i r anxiety yet s t i l l remained w i t h i n the normal range. He concluded that a s i n g l e bout of e x e r c i s e d i d reduce anxiety i n anxious students but tha t the arous a l l e v e l of the low anxious students was increa s e d during e x e r c i s e . Abood (1984) examined the e f f e c t s of acute p h y s i c a l e x e r c i s e on s t a t e anxiety and mental performance of c o l l e g e women. State anxiety was assessed by the S t a t e - T r a i t Inventory and the d i g i t s backwards subtest of the Wechsler Adult I n t e l l i g e n c e Scale (Wechsler, 1958) was used to measure mental 20 performance. Participants were selected who scored i n the upper and lower 30 percent on the STAI. Participants from each of these conditions were randomly assigned to either the experimental or control groups. The experimental group completed the state anxiety form of STAI before and afte r bench-steppping 30 times a minute for 5 minutes. The control groups were asked to rest for 5 minutes i n a comfortable chair between the pre- and post-anxiety t e s t . Both the experimental and the control groups had lower post-anxiety scores than on the pre-anxiety t e s t . State anxiety however was not s i g n i f i c a n t l y reduced i n the highly anxious women, but there was a trend i n that d i r e c t i o n . Abood suggested that one interp r e t a t i o n might be that the in t e n s i t y of exercise was not s u f f i c i e n t . The low anxious women experienced a s i g n i f i c a n t increase i n t h e i r state anxiety, yet t h e i r anxiety l e v e l s remained within normal range. Abood (1984) att r i b u t e d t h i s to a heightened arousal state a f t e r a short bout of exercise. de Vries (1968) examined the si t u a t i o n from a s l i g h t l y d i f f e r e n t perspective. His investigations looked at the ef f e c t of exercise on muscular tension. The tension as measured electomyographically, was s i g n i f i c a n t l y reduced following vigorous exercise, de Vries and Adams (1972) investigated the eff e c t s of single doses of exercise and meprobamate (a t r a n q u i l i z e r drug) as to the ef f e c t on muscular tension. The part i c i p a n t s who exercised had greater decreases i n muscle tension than the group who received the t r a n q u i l i z e r s . In summary , n o t a l l o f t h e s e i n v e s t i g a t i o n s h a d a c o n t r o l g r o u p n o r d i d t h e y e x a m i n e e x e r c i s e a s a t r e a t m e n t o v e r a p e r i o d o f t i m e . The d i f f e r e n t i a l e f f e c t s o f i n t e n s i t y a n d t y p e o f e x e r c i s e on a n x i e t y c a n n o t be e x a m i n e d i n a s i n g l e b o u t o f e x e r c i s e . The r e s u l t s were i n c o n c l u s i v e . T h e r e was no s i g n i f i c a n t d i f f e r e n c e s i n d e c r e m e n t s i n s t a t e a n x i e t y f o r t h e c o n t r o l a n d e x p e r i m e n t a l g r o u p s ; m a l e s s h o w e d a d e c r e a s e i n a n x i e t y w h e r e a s f e m a l e s d i d n o t ; a n d t h e l e s s a n x i o u s f e m a l e s i n c r e a s e d t h e i r s t a t e a n x i e t y . T h e s e s t u d i e s a r e a l s o l i m i t e d i n t h a t t h e y do n o t e x a m i n e t r a i t a n x i e t y , w h e r e a s s t a t e a n x i e t y i s an e m o t i o n a l r e a c t i o n o f an i n t e n s i t y w h i c h i s g e n e r a t e d b y t h e s i t u a t i o n o f t h e moment . In e x a m i n i n g t h e e f f e c t o f a s i n g l e b o u t o f e x e r c i s e on s t a t e a n x i e t y , t h e r e s e a r c h e r i s r e c e i v i n g a v e r y b i a s e d l o o k a t an e m o t i o n a l r e a c t i o n a s i t t a p s o n l y t h e e x p e r i m e n t a l s i t u a t i o n . The r e s e a r c h e r s i n t h e f o l l o w i n g s e c t i o n h a v e a t t e m p t e d t o l o o k a t t h e r a m i f i c a t i o n s o f an e x e r c i s e p r o g r a m u p o n m o o d . The e x e r c i s e p r o g r a m s e x a m i n e d were a t l e a s t 4 - w e e k s i n l e n g t h a n d f o l l o w e d t h e p r e s c r i b e d f i t n e s s g u i d e l i n e s f o r t h e p a r t i c u l a r p r o g r a m o f f e r e d . T h u s g i v i n g an e x t e n d e d t i m e f r a m e i n t h e i n v e s t i g a t i o n o f e x e r c i s e on a n x i e t y . E f f e c t s o f an E x e r c i s e P r o g r a m F o l k i n s , L y n c h , a n d G a r d n e r (1972) were f o r e r u n n e r s i n e x a m i n i n g t h e e f f e c t s o f an e x e r c i s e t r e a t m e n t p r o g r a m u p o n m o o d . T h e y s u b m i t t e d 44 j u n i o r c o e d c o l l e g e s t u d e n t s t o a s e m e s t e r j o g g i n g p r o g r a m a n d f o u n d i m p r o v e m e n t i n t h e i r 22 depression and p h y s i c a l f i t n e s s . These researchers concluded t h a t the students who were i n poorest p h y s i c a l and emotional h e a l t h appeared t o b e n e f i t the most from the program. F o l k i n s (1976) examined the e f f e c t s of an e x e r c i s e treatment program on the mood of high coronary r i s k males. The ex e r c i s e group p a r t i c i p a t e d i n 3 e x e r c i s e c l a s s e s per week f o r 12 weeks. A f t e r the program, he looked at the p h y s i c a l and p s y c h o l o g i c a l changes from pre- to p o s t - e x e r c i s e f o r both the ex e r c i s e group and the c o n t r o l group. Anxiety and depression s c a l e s from the " i n general" v e r s i o n of the M u l t i p l e A f f e c t A d j e c t i v e C h e c k l i s t (Zuckerman & Lubin, 1965) were used. S i g n i f i c a n t decreases i n anxiety and depression were found only i n the e x e r c i s e group. Researchers s h i f t e d from examining the e f f e c t s of an e x e r c i s e program versus a s i n g l e bout of e x e r c i s e to examining the e f f e c t s of an e x e r c i s e program f o r people who were not p a r t i c u l a r l y s t r e s s e d . The focus of t h i s research was an extension i n t o the realm of the p a r t i c i p a n t ' s p s y c h o l o g i c a l s t a t e . E f f e c t s of e x e r c i s e program on the minimally s t r e s s e d . Eby (1984) i n v e s t i g a t e d the e f f e c t s of an aerobic e x e r c i s e program on t r a i t a nxiety as measured by STAI and depression as measured by Zung S e l f - r a t i n g Depression Scale (Zung, 1965). Graduate and undergraduate students were s o l i c i t e d and randomly assigned t o 4 groups (delayed treatment, weight t r a i n i n g , jogging, and a combination of weight t r a i n i n g and 23 j o g g i n g ) . The t r e a t m e n t was 6 weeks o f i n d i v i d u a l p r o g r a m m i n g i n e a c h g r o u p w i t h l i t t l e t o no g r o u p i n t e r a c t i o n . The a e r o b i c g r o u p s h o w e d s i g n i f i c a n t i m p r o v e m e n t f r o m p r e - t o p o s t - t e s t i n t h e e s t i m a t i o n o f t h e i r maximum o x y g e n u p t a k e b u t t h e r e was no s i g n i f i c a n t c h a n g e i n t h e a n x i e t y a n d d e p r e s s i o n s c o r e s . T h e r e was a t r e n d t o w a r d s i g n i f i c a n t c h a n g e w i t h i n e a c h e x e r c i s e g r o u p , t h e l o w e s t p o s t t e s t c e l l means o c c u r r i n g i n t h e f o l l o w i n g o r d e r ; a e r o b i c g r o u p , c o m b i n a t i o n g r o u p , w e i g h t t r a i n i n g g r o u p , a n d d e l a y e d t r e a t m e n t g r o u p . A s t u d y b y B l u m e n t h a l e t a l . (1982) a s s e s s e d t h e e f f e c t s o f a r e o b i c e x e r c i s e on t h e p s y c h o l o g i c a l f u n c t i o n i n g o f a n o n c l i n i c a l s a m p l e o f h e a l t h y m i d d l e - a g e d a d u l t s . T h e r e were 16 p a r t i c i p a n t s i n b o t h t h e e x p e r i m e n t a l a n d c o n t r o l g r o u p s . The e x p e r i m e n t a l g r o u p p a r t i c i p a t e d i n a 10 -week w a l k - j o g p r o g r a m , w h e r e a s t h e m a t c h e d c o n t r o l g r o u p m a i n t a i n e d t h e i r s e d e n t a r y l i f e s t y l e s . The p a r t i c i p a n t s c o m p l e t e d a b a t t e r y o f p s y c h o l o g i c a l t e s t s ( P r o f i l e o f M o o d s ; M c N a i r , L o r r , & D r o p p l e m a n , 1 9 7 1 ; S T A I ; a n d a r e t r o s p e c t i v e q u e s t i o n n a i r e r e g a r d i n g s e l f - p e r c e p t i o n s o f c h a n g e ) p r e - a n d p o s t - e x e r c i s e p r o g r a m . E x a m i n a t i o n o f t e s t s c o r e s r e v e a l e d t h a t t h e e x e r c i s e g r o u p i m p r o v e d s i g n i f i c a n t l y i n t h e i r s t a t e - t r a i t a n x i e t y s c o r e s a n d t h e t e n s i o n , d e p r e s s i o n a n d f a t i q u e s u b s c a l e s o f t h e P r o f i l e o f Moods s c o r e s , c o m p a r e d w i t h t h e c o n t r o l g r o u p . The c o n t r o l g r o u p r e m a i n e d t h e same o r s h o w e d d e t e r i o r a t i o n on c e r t a i n s c o r e s . T h e y c o n c l u d e d t h a t t h e r e was a p o t e n t i a l u t i l i t y o f r e g u l a r a e r o b i c e x e r c i s e i n p r o m o t i n g p s y c h o l o g i c a l h e a l t h i n n o r m a l a d u l t s . M c G l y n n , F r a n k l i n , L a u r o , a n d M c G l y n n (1983) s t u d i e d t h e e f f e c t o f a e r o b i c c o n d i t i o n i n g a n d i n d u c e d s t r e s s on s t a t e -t r a i t a n x i e t y , b l o o d p r e s s u r e , a n d m u s c l e t e n s i o n . T h e y i n v e s t i g a t e d t h e e f f e c t s o f a 14 -week i n d i v i d u a l i z e d a e r o b i c c o n d i t i o n i n g p r o g r a m . The p a r t i c i p a n t s were d r a w n f r o m an u n d e r g r a d u a t e p o p u l a t i o n . The e x p e r i m e n t a l g r o u p p a r t i c i p a t e d i n an a e r o b i c c l a s s a n d were s e d e n t a r y p r i o r t o j o i n i n g t h e c l a s s , w h e r e a s t h e c o n t r o l g r o u p was f o r m e d f r o m h e a l t h s c i e n c e s c l a s s e s . B a s e l i n e m e a s u r e s were t a k e n b e f o r e t h e t r e a t m e n t p r o g r a m b e g a n on a l l o f t h e v a r i a b l e s b e i n g i n v e s t i g a t e d . A t t h e e n d o f t h e 14 -week p r o g r a m , p a r t i c i p a n t s f r o m b o t h g r o u p s were r e t e s t e d a n d a l s o s u b j e c t e d t o a s t r e s s f u l i n t e r v e n t i o n . The c o n d i t i o n e d g r o u p s h o w e d a s i g n i f i c a n t i n c r e a s e i n c a r d i o - v a s c u l a r e n d u r a n c e (as m e a s u r e d b y S h a r k e y ' s (1979) s t e p t e s t ) . T h e r e were no s i g n i f i c a n t d i f f e r e n c e s b e t w e e n g r o u p s f o r s t a t e a n d t r a i t a n x i e t y b u t t h e r e were s i g n i f i c a n t d i f f e r e n c e s i n t h e e l e c t r o m y o g r a p h i c m e a s u r e m e n t s . Nagy a n d F r a z i e r (1988) h y p o t h e s i z e d t h a t s e d e n t a r y p a r t i c i p a n t s w o u l d h a v e p o s i t i v e g a i n s on moods a s an o u t c o m e o f a s h o r t - t e r m (15 week) e x e r c i s e p r o g r a m , c o m p a r e d w i t h p a r t i c i p a n t s who e x e r c i s e d r e g u l a r l y p r i o r t o t h e 1 5 - w e e k e x e r c i s e p r o g r a m . T h e y a l s o e x a m i n e d t h e r e l a t i o n s h i p s among e x e r c i s e , l o c u s o f c o n t r o l , a n d s e l f e s t e e m . Mood s t a t e s were a s s e s s e d u s i n g t h e P r o f i l e o f Mood S t a t e s (POMS) b e f o r e a n d a f t e r treatment. The pre- and post-measures on the mood states were not s i g n i f i c a n t l y d i f f e r e n t for either group, i n d i c a t i n g that the hypothesis that a sedentary group of people s t a r t i n g an exercise program would have p o s i t i v e gains on moods was not supported. The locus of control and the self-esteem scores showed minimal v a r i a t i o n between the two groups. Simons and Birkimer (1988) however found a mood enhancement e f f e c t i n t h e i r experimental group, compared with the control group. They also used the POMS measure for mood. Mood improvement was s i g n i f i c a n t l y d i f f e r e n t in the following subscales of the POMS; anger, anxiety, and confusion. Depression was decreased s i g n i f i c a n t l y only from pretest to follow-up. The participants i n the 8-week aerobic class also showed an improvement in t h e i r f i t n e s s l e v e l s . Three months aft e r the program, the participants continued to show an improvement i n t h e i r mood states but the extent of exercise over that period was not measured. Despite changes i n the mood state measures there were no changes in the group's locus of control measures. Hughes et a l . (1986) argued that many previous studies were poorly designed or used inappropriate measures that affected the outcomes. They tested the eff e c t of a 12-week exercise program on the mood of sedentary men who were "free of psychopathology 1 1 i n a randomized cross-over design. The part i c i p a n t s were randomly assigned to either an exercise program or a control group (maintenance of sedentary 26 l i f e s t y l e ) and then switched t o the converse c o n d i t i o n . The e x e r c i s e was n o n s o c i a l and of moderate i n t e n s i t y . The e x e r c i s e r s improved i n the t r e a d m i l l d u r a t i o n t e s t but not the maximum oxygen uptake t e s t . The t o t a l mood or any of the POMS subscales improved more during the e x e r c i s e p e r i o d than during the c o n t r o l p e r i o d . They concluded that e x e r c i s e alone i s i n s u f f i c i e n t t o produce p s y c h o l o g i c a l b e n e f i t s , " i . e . , e i t h e r psychopathology, s o c i a l i z a t i o n , or a t r a i n i n g e f f e c t must be present f o r e x e r c i s e to produce p s y c h o l o g i c a l b e n e f i t s " (p. 359) . The r e s u l t s continue to be mixed with regard to the e f f i c a c y of e x e r c i s e as a treatment f o r a n x i e t y . The q u a l i t y of the research improved i n that researchers t e s t e d f i t n e s s improvements w i t h i n t h e i r s t u d i e s , and examined d i f f e r e n c e s between types of e x e r c i s e . However, the p a r t i c i p a n t s were of t e n drawn from a pop u l a t i o n that might have d e f i n i t e values concerning e x e r c i s e because they came from h e a l t h science courses or had been about to j o i n a f i t n e s s c l a s s . The p a r t i c i p a n t s i n these s t u d i e s were not p a r t i c u l a r l y s t r e s s e d . Perhaps p a r t i c i p a n t s with greater s t r e s s l e v e l s would r e s u l t i n d i f f e r e n t outcomes. E f f e c t s of e x e r c i s e program on the s t r e s s e d . A c o n t r o l l e d , randomized design that accounts f o r a s o c i a l i z i n g e f f e c t was conducted by Moses et a l . (1989). The study compared the e f f e c t s of two, 10-week aerobic t r a i n i n g programs of d i f f e r i n g i n t e n s i t i e s on mood and mental w e l l - b e i n g w i t h t h o s e o f a c r e d i b l e a t t e n t i o n - p l a c e b o c o n d i t i o n . S e d e n t a r y a d u l t s f r o m t h e l o c a l p o p u l a t i o n were a s s i g n e d t o one o f f o u r c o n d i t i o n s : h i g h e x e r c i s e (60-90% maximum H R ) , m o d e r a t e e x e r c i s e (60% o f maximum H R ) , a t t e n t i o n - p l a c e b o ( s t r e n g t h a n d f l e x i b i l i t y e x e r c i s e s ) , a n d w a i t l i s t . The p a r t i c i p a n t s were t e s t e d p r e - a n d p o s t - e x e r c i s e p r o g r a m on f i t n e s s a n d p s y c h o l o g i c a l m e a s u r e s . POMS was u s e d t o e v a l u a t e t h e e f f e c t s o f t h e e x p e r i m e n t a l c o n d i t i o n s on p s y c h o l o g i c a l w e l l - b e i n g . A s e r i e s o f s c a l e s were d e v e l o p e d f o r t h i s s t u d y f o r t h e e v a l u a t i o n o f p e r c e i v e d c o p i n g a b i l i t y . C o o p e r ' s 1 2 - m i n u t e w a l k - r u n t e s t s h o w e d an o r d e r l y p r o g r e s s i o n o f i m p r o v e m e n t f o t h e . a e r o b i c t r a i n i n g g r o u p s , w i t h t h e g r e a t e s t c h a n g e i n h i g h e x e r c i s e a n d m i n i m a l c h a n g e i n t h e a t t e n t i o n - p l a c e b o c o n d i t i o n . T h e r e was a s i g n i f i c a n t i m p r o v e m e n t i n t h e s u b s c a l e s o f t e n s i o n / a n x i e t y a n d c o n f u s i o n o f t h e POMS w i t h t h e m o d e r a t e e x e r c i s e c o n d i t i o n b u t n o t t h e h i g h e x e r c i s e o r a t t e n t i o n - p l a c e b o c o n d i t i o n s . The p e r c e i v e d c o p i n g a b i l i t y s h o w e d an i m p r o v e m e n t f r o m p r e - t o f o l l o w - u p t e s t i n g i n t h e m o d e r a t e e x e r c i s e c o n d i t i o n . S t e p t o e e t a l . (1989) r e p l i c a t e d t h e i r p r e v i o u s s t u d y w i t h an a n x i o u s g r o u p o f a d u l t s f r o m t h e g e n e r a l p o p u l a t i o n . The p s y c h o l o g i c a l e f f e c t s o f a m o d e r a t e a e r o b i c e x e r c i s e p r o g r a m were c o m p a r e d t o an a t t e n t i o n - p l a c e b o c o n d i t i o n . The S T A I was a d d e d t o t h e p s y c h o l o g i c a l m e a s u r e s . T h e r e were s i g n i f i c a n t i m p r o v e m e n t s i n a e r o b i c f i t n e s s i n t h e ' m o d e r a t e e x e r c i s e g r o u p a s c o m p a r e d t o t h e a t t e n t i o n - p l a c e b o c o n d i t i o n 28 S i g n i f i c a n t group d i f f e r e n c e s e x i s t e d p o s t - t r a i n i n g on POMS te n s i o n / a n x i e t y , confusion, depression and on perceiv e d coping a b i l i t i e s . No s i g n i f i c a n t d i f f e r e n c e s were shown between groups p o s t - t r a i n i n g on t e s t s of t r a i t a n x i e t y . There were main e f f e c t s of se s s i o n , with session as the w i t h i n - s u b j e c t f a c t o r (ANOVA), i n t r a i t a n xiety. This r e f l e c t e d the general decrease i n t r a i t a nxiety that was reported by both groups. The p s y c h o l o g i c a l e f f e c t s were maintained on the 3-month follow-up. Long (1984) compared the e f f e c t i v e n e s s of an aerobic c o n d i t i o n i n g program (jogging), s t r e s s i n o c u l a t i o n t r a i n i n g , and a wait l i s t c o n t r o l i n the treatment of chronic i n t e r m i t t e n t s t r e s s . The s t r e s s e d p a r t i c i p a n t s were randomly assigned to one of three groups. The treatment program was conducted i n two waves—a time-lagged crossover design. The wait l i s t group was randomly assigned to e i t h e r an e x e r c i s e or s t r e s s i n o c u l a t i o n group a f t e r the i n i t i a l program was completed. The f i t n e s s and s t r e s s e v a l u a t i o n s were done p r e t e s t , p o s t t e s t and 12-week follow-up. P a r t i c i p a n t s i n the jogging program were placed on a pr o g r e s s i v e walk/jog regime and were encouraged to g r a d u a l l y increase t h e i r d i s t a n c e and decrease t h e i r time. These p a r t i c i p a n t s d i d experience s i g n i f i c a n t decrements i n s t a t e and t r a i t a n x i e t y (as measured by STAI) which were maintained or improved i n a 3-month follow-up. Wilson (1985) a l s o examined e x e r c i s e as a p o s s i b l e 29 treatment f o r reducing the s t r e s s response i n nurses. She argues th a t nurses are u s u a l l y s t r e s s e d due to t h e i r o c c u p a t i o n a l d i f f i c u l t i e s . T h i r t y - f o u r nurses were randomly assigned t o a 16-week aerobic e x e r c i s e program or a c o n t r o l group. Aerobic e x e r c i s e c o n s i s t e d of an i n d i v i d u a l i z e d p r o g r e s s i v e walk/jog program 3 times per week. A l l p a r t i c i p a n t s had t h e i r b a s e l i n e l e v e l s of f i t n e s s , p h y s i o l o g i c - b i o c h e m i c a l and p s y c h o l o g i c a l taken p r i o r t o the s t a r t of the program and once again post program. The r e s u l t s i n d i c a t e d t h a t the e x e r c i s e group increased t h e i r oxygen / u p t a k e , decreased t h e i r A.M. r e s t i n g heart r a t e and s y s t o l i c blood pressure. State anxiety was s i g n i f i c a n t l y reduced i n the e x e r c i s e group but not t r a i t anxiety (as measured by STAI) when compared to the c o n t r o l group. The p h y s i o l o g i c measure of s t r e s s was found to be equal between the e x e r c i s e and c o n t r o l groups. The Zung (Zung, 1965) measure f o r depression a l s o showed a r e d u c t i o n i n the e x e r c i s e r s ' depression l e v e l s . In her concluding arguments, Wilson s t a t e s "since the r e s u l t s of t h i s study have shown that e x e r c i s e was s t r e s s reducing, h o s p i t a l a d m i n i s t r a t i o n and nursing management should consider •exercise an important component i n the p l a n n i n g of a s t r e s s management program" (p. 205). Setaro (1985) compared the e f f e c t i v e n e s s of d i f f e r e n t combinations of aerobic e x e r c i s e and group counseling i n a 10-week treatment program of anxiety and depression. P a r t i c i p a n t s a n x i e t y and depression as measured by s c a l e s #2 and #7 on the 30 M i n n e s o t a M u l t i p h a s i c P e r s o n a l i t y I n v e n t o r y (MMPI; H a t h a w a y & M c k i n l e y , 1943) were t e s t e d p r e - a n d p o s t - p r o g r a m . P a r t i c i p a n t s e n t e r i n g t h e t r e a t m e n t p r o g r a m were e x p e r i e n c i n g m i l d t o m o d e r a t e d e p r e s s i o n a n d a n x i e t y (T s c o r e r a n g e o f 60 t h r o u g h 75 on s c a l e s #2 a n d #7 o f t h e M M P I ) . A n x i e t y i n t h i s i n s t r u m e n t i s s u p p o s e d t o m e a s u r e t r a i t a n x i e t y . One h u n d r e d a n d f i f t y p a r t i c i p a n t s were r a n d o m l y a s s i g n e d t o e i t h e r c o g n i t i v e g r o u p c o u n s e l l i n g a n d a e r o b i c d a n c e , a r e o b i c d a n c e , c o g n i t i v e g r o u p c o u n s e l l i n g , c o g n i t i v e g r o u p c o u n s e l l i n g a n d n o n - a e r o b i c a c t i v i t y ( a r t s & c r a f t s ) , n o n - a e r o b i c a c t i v i t y a n d no t r e a t m e n t g r o u p s . The d a t a were s u b j e c t e d t o a m u l t i v a r i a t e a n a l y s i s o f v a r i a n c e f o l l o w e d by a p r i o r i o r t h o g o n a l c o n t r a s t s . The r e s u l t s i n d i c a t e d t h a t (a) t h e e f f e c t o f a l l t r e a t m e n t s were g r e a t e r t h a n no t r e a t m e n t ; (b) c o g n i t i v e g r o u p c o u n s e l l i n g h a d a g r e a t e r e f f e c t t h a n e i t h e r a e r o b i c o r n o n -a e r o b i c c o n d i t i o n s i n t h e t r e a t m e n t o f d e p r e s s i o n a n d a n x i e t y ; (c) a e r o b i c e x e r c i s e was more e f f e c t i v e t h a n t h e n o n - a e r o b i c c o n d i t i o n i n t h e t r e a t m e n t o f d e p r e s s i o n b u t n o t a n x i e t y ; (d) t h e c o m b i n a t i o n o f c o g n i t i v e g r o u p c o u n s e l l i n g a n d e i t h e r a e r o b i c o r n o n - a e r o b i c a c i t i v i t y was more e f f e c t i v e i n t h e t r e a t m e n t o f d e p r e s s i o n b u t n o t a n x i e t y t h a n g r o u p c o u n s e l l i n g a l o n e ; (e) t h e c o m b i n a t i o n o f c o g n i t i v e g r o u p c o u n s e l l i n g a n d a e r o b i c e x e r c i s e was more e f f e c t i v e t h a n g r o u p c o u n s e l l i n g a n d n o n - a e r o b i c a c t i v i t y i n t h e t r e a t m e n t o f d e p r e s s i o n b u t n o t a n x i e t y . S e t a r o s u g g e s t s t h a t a e r o b i c e x e r c i s e i n t h e t r e a t m e n t o f a n x i e t y d i f f e r s a c c o r d i n g t o t h e t y p e o f a n x i e t y 31 t r e a t e d . He s u g g e s t s t h a t s t a t e a n x i e t y m i g h t be more a f f e c t e d b y a e r o b i c e x e r c i s e t h a n t r a i t a n x i e t y . He c o n c l u d e s t h a t a s d e p r e s s i o n a n d s t a t e a n x i e t y a p p e a r t o r e s p o n d t o e x e r c i s e t r e a t m e n t i t s h o u l d be i n c o r p o r a t e d i n t o o c c u p a t i o n a l a n d i n d u s t r i a l s e t t i n g s . L o n g a n d H a n e y (1988) c o m p a r e d two s t r e s s r e d u c t i o n i n t e r v e n t i o n s ( a e r o b i c e x e r c i s e a n d p r o g r e s s i v e r e l a x a t i o n e x e r c i s e s ) i n t h e t r e a t m e n t o f s t r e s s . F i f t y s t r e s s e d , s e d e n t a r y , w o r k i n g women were r a n d o m l y a s s i g n e d t o e i t h e r g r o u p f o r an 8 -week t r e a t m e n t p r o g r a m . The p a r t i c i p a n t s i d e n t i f i e d a t l e a s t two p e r s i s t e n t w o r k - r e l a t e d s t r e s s o r s a n d s c o r e d 5 o r a b o v e on W a l k ' s (1956) T e n s i o n T h e r m o m e t e r . The i n s t r u m e n t s u s e d t o m e a s u r e s t r e s s p r e t e s t , p o s t t e s t a n d f o l l o w - u p w e r e t h e STAI T r a i t A n x i e t y I n v e n t o r y ; The G e n e r a l S e l f - E f f i c a c y S c a l e ( S h e r e r e t a l . , 1 9 8 2 ) ; a n d t h e ways o f C o p i n g C h e c k l i s t ( L a z a r u s & F o l k m a n , 1 9 8 4 ) . The e x e r c i s e g r o u p p a r t i c i p a t e d i n a p r o g r e s s i v e w a l k - j o g p r o g r a m w h i l e t h e r e l a x a t i o n g r o u p p r a c t i s e d B e r s t e i n a n d B o r k o v e c ' s (1973) p r o g r e s s i v e m u s c l e r e l a x a t i o n . B o t h g r o u p s r e d u c e d t h e i r t r a i t a n x i e t y f r o m p r e - t o p o s t t r e a t m e n t w i t h f u r t h e r r e d u c t i o n s a t 8 -week f o l l o w - u p . T h e i r s e l f - e f f i c a c y i n c r e a s e d f r o m p r e - t o p o s t t r e a t m e n t a n d was m a i n t a i n e d a t f o l l o w - u p . T h e c o p i n g s t r a t e g i e s o f t h e p a r t i c i p a n t s d i d n o t s i g n i f i c a n t l y c h a n g e a t e i t h e r p o s t t r e a t m e n t o r f o l l o w - u p . The r e s e a r c h e r s d e t e r m i n e d t h a t t h e s t u d y t e n d e d t o s u p p o r t t h e g e n e r a l c o n l u s i o n t h a t p a r t i c i p a t i o n i n a e r o b i c e x e r c i s e o r p r o g r e s s i v e r e l a x a t i o n 32 programs could have p o t e n t i a l i n h e l p i n g decrease a n x i e t y and increase s e l f - e f f i c a c y i n sedentary, s t r e s s e d working women. Once again there are mixed r e s u l t s regarding the e f f e c t i v e n e s s of e x e r c i s e i n t r e a t i n g s t r e s s e d people. The d e s c r i p t i v e s t a t i s t i c s i n d i c a t e that the p a r t i c i p a n t s w i t h i n an e x e r c i s e program d i d show some improvement but the c o n t r a s t between a c o n t r o l group or a comparison group showed no s i g n i f i c a n t d i f f e r e n c e s i n improvement. However, the q u a l i t y of the research has improved. Moses et a l . (1989) and Steptoe et a l . (1989) designed s t u d i e s that c o n t r o l l e d f o r s o c i a l i z a t i o n e f f e c t s , and examined d i f f e r e n c e s i n e x e r c i s e . i n t e n s i t i e s and f i t n e s s improvements. The f i n a l group of s t u d i e s to be reviewed i n v e s t i g a t e d the d i f f e r e n c e s between f i t and u n f i t peoples' responses to s t r e s s o r s . This p a r t i c u l a r l i n e of research examines the p h y s i o l o g i c a l and p s y c h o l o g i c a l e f f e c t s of an e x e r c i s e program before and a f t e r s t r e s s i n g the p a r t i c i p a n t s . F i t / u n f i t people's r e a c t i o n to s t r e s s o r s . L i k e McGlynn et a l . (1983), some researcher decided to approach the problem of the e f f e c t i v e n e s s of e x e r c i s e as a s t r e s s management technique from the p e r s p e c t i v e of viewing how f i t and u n f i t people . respond to s t r e s s o r s . In McGlynn's study the c o n d i t i o n e d group d i d not show a s i g n i f i c a n t increase i n blood pressure as was the case i n the c o n t r o l group. A f t e r being subjected to a s t r e s s f u l c o g n i t i v e task, both groups d i d show s i g n i f i c a n t i ncreases i n muscle t e n s i o n and s t a t e anxiety, although the 33 c o n t r o l group's mean increases were markedly higher than the co n d i t i o n e d group's means. K e l l e r and :Seraganian (1984) conducted two s t u d i e s t o determine the i n f l u e n c e of aerobic f i t n e s s l e v e l on autonomic r e a c t i v i t y t o p s y c h o s o c i a l s t r e s s . The f i r s t study used 45 men who were t r a i n e d , untrained, or were i n t r a i n i n g t o t e s t t h e i r autonomic r e a c t i v i t y (as measured by l a b i l i t y i n electrodermal a c t i v i t y ) to two speeded mental tasks designed t o induce p s y c h o s o c i a l s t r e s s . The men were t e s t e d at 3-week i n t e r v a l s over 9-weeks. At the i n i t i a l t e s t the t r a i n e d men showed f a s t e r autonomic recovery from t h i s s t r e s s than d i d the unt r a i n e d or t r a i n i n g men. In the f o l l o w i n g t e s t s the 3 groups were s i m i l a r i n t h e i r autonomic responses. The second study employed 60 p a r t i c i p a n t s who were randomly assigned to 10-week aerobic e x e r c i s e , meditation, or music a p p r e c i a t i o n programs. Once again the p a r t i c i p a n t s were subjected t o two p s y c h o s o c i a l s t r e s s o r s t h a t were administered at week 2, 6, and 10 of the treatment program. P a r t i c i p a n t s improved s i g n i f i c a n t l y i n t h e i r f i t n e s s l e v e l s and a l s o showed f a s t e r recovery i n the electrodermal response to the s t r e s s o r s . The researchers i n f e r r e d t h a t the quicker autonomic recovery perhaps allows the a e r o b i c a l l y f i t person t o cope more e f f e c t i v e l y w i t h emotional s t r e s s . Holmes and Roth (1985) examined the e f f e c t s of a s t r e s s f u l task on high and low f i t s u b j e c t s . S i t t i n g q u i e t l y d u r i n g a b a s e l i n e p e r i o d t h e i r pulse r a t e and l e v e l s of s u b j e c t i v e a r o u s a l were assessed. Analyses showed th a t task performance r e s u l t e d i n general increases i n pulse r a t e s and s u b j e c t i v e c o g n i t i v e a r o u s a l , and s u b j e c t i v e somatic a r o u s a l . The h i g h - f i t group however evinced smaller pulse r a t e increases i n response to s t r e s s o r s than d i d the low f i t group. Both groups were s i m i l a r i n the s u b j e c t i v e responses to the s t r e s s o r s . Holmes and Roth concluded that t h e i r r e s u l t s were c o n s i s t e n t w i t h a growing body of research which i n d i c a t e s that aerobic f i t n e s s i s a s s o c i a t e d with reduced p h y s i o l o g i c a l r e a c t i v i t y to p s y c h o s o c i a l s t r e s s . M c G i l l e y and Holmes (1988) conducted a s i m i l a r study of high- and l o w - f i t p a r t i c i p a n t ' s r e a c t i v i t y to s t r e s s . They found that the high f i t group evinced r e l i a b l y smaller c a r d i o v a s c u l a r responses (blood pressure and heart rate) t o a s t r e s s f u l c o g n i t i v e t e s t and a l s o reported smaller increases i n c o g n i t i v e and somatic arousal than the l o w - f i t group. I n v e s t i g a t i n g the e f f e c t i v e n e s s of e x e r c i s e as a s t r e s s reducer from t h i s p a r t i c u l a r p e r s p e c t i v e adds to the confusion of the r e s u l t s t o date. Although people's c a r d i o v a s c u l a r responses might d i f f e r between f i t and u n f i t people, t h e i r p s y c h o l o g i c a l responses do not always d i f f e r . This could be due, i n p a r t , because one's perception of s t r e s s plays a l a r g e r o l e i n one's p s y c h o l o g i c a l s t r e s s responses (Lazarus & Folkman, 1984). I f s t r e s s o r s depend on a person's pe r c e p t i o n of what i s or i s not threatening/harmful, then c o n t r i v e d s t r e s s o r s w i t h i n an experimental s i t u a t i o n might not 35 n e c e s s a r i l y be s t r e s s f u l to. a l l the p a r t i c i p a n t s . Summary In summary, although most st u d i e s reviewed evinced some change on s t r e s s measures, not a l l measures showed a s i g n i f i c a n t change. The researchers reported that there had been some e f f e c t , "a tr e n d i n the given d i r e c t i o n " no matter how small the change. Perhaps t h a t , i n p a r t , determines the p o p u l a r i z e d view that e x e r c i s e i s an e f f e c t i v e s t r e s s reducer. A great deal of i n c o n c l u s i v e research e x i s t s i n t h i s area. Given the need to evaluate the e f f e c t of e x e r c i s e on s t r e s s s i n c e e x e r c i s e i s being widely p r e s c r i b e d as e f f e c t i v e , i t would be a waste to continue adding to t h i s body of i n c o n c l u s i v e knowledge. Instead the present i n f o r m a t i o n must be i n t e g r a t e d i n order to provide some answers and provide d i r e c t i o n f o r f u t u r e research. Although each study asks i t s own p a r t i c u l a r questions, there i s an u n d e r l y i n g p a t t e r n t o the questions being asked. This e v o l v i n g p a t t e r n appears t o be concerned w i t h the f o l l o w i n g questions: i s e x e r c i s e an e f f e c t i v e s t r e s s reducer? what type of person b e n e f i t s most from e x e r c i s e ? and which type of e x e r c i s e i s of most b e n e f i t i n s t r e s s reduction? The meta-analytic approach allows the researcher t o i n t e g r a t e the present body of s t u d i e s i n order to answer these questions and a l s o to consider the v a r i a b l e s which w i l l , i n f l u e n c e the variance i n study outcomes. Meta-analysis In 1977, Glass introduced a q u a n t i t a t i v e method 36 (meta-analysis) f o r i n t e g r a t i n g the f i n d i n g s of many research s t u d i e s on a common theme. He coined the term meta-analysis t o convey the idea that there were ways to q u a n t i t a t i v e l y summarize many i n d i v i d u a l s t u d i e s . Meta-analysis i s defined as "the s t a t i s t i c a l a n a l y s i s of summary f i n d i n g s of many e m p i r i c a l s t u d i e s " (Glass et a l . , 1981, p. 21). T r a d i t i o n a l l y , researchers r e l i e d upon n a r r a t i v e reviews f o r a s sessing the accumulated knowledge of a s p e c i f i c t o p i c i n a given f i e l d . The purposes of reviews vary according t o the researchers primary i n t e r e s t and may focus on asse s s i n g new substa n t i v e and/or methodological developments i n a given f i e l d ; v e r i f y i n g e x i s t i n g t h e o r i e s ; s y n t h e s i z i n g knowledge from v a r i o u s f i e l d s of research; or i n f e r r i n g g e n e r a l i z a t i o n s about issues from a set of st u d i e s examining those i s s u e s . The l a t t e r purpose f o r a review i s c a l l e d an i n t e g r a t i v e review. Although each of these reviews have methods, techniques, and procedures that, guide the researchers assessment of the knowledge being reviewed, these reviews are not r e f i n e d or rigo r o u s enough t o adequately capture the o v e r a l l meaning of a la r g e body of s t u d i e s (Jackson, 1980). Glass et a l . (1981) contend that "the reviewer i s even l e s s able to absorb the sense of a hundred research s t u d i e s than the observer i s able to scan a hundred t e s t scores and, without r e l i a n c e on s t a t i s t i c a l methods, absorb the sense of t h e i r s i z e and spread, and c o r r e l a t i o n s " (p. 14). The e v o l u t i o n of i n t e g r a t i v e reviews has been molded by 37 the r a p i d growth of research i n the f i e l d s of education, behavioural and s o c i a l sciences, e x e r c i s e and h e a l t h . Research has r e s u l t e d i n many divergent outcomes on any one t o p i c w i t h i n a given f i e l d . Due t o the d i v e r s i t y of research outcomes on a s p e c i f i c hypothesis, Glass (1976) thought the attempts t o make sense of the p r o l i f e r a t i o n of the same body of knowledge must be of a rigorous and q u a n t i t a t i v e nature. He thought t h a t t h i s approach would be able to show the r e g u l a r p a t t e r n s d i s c e r n a b l e w i t h i n a body of s t u d i e s i n a s i m i l a r area of research. B r i e f H i s t o r y of Meta-analysis The e a r l y roots of meta-analysis began i n the f i e l d of a g r i c u l t u r a l experimentation. The f i e l d of a g r i c u l t u r a l experimentation had s e v e r a l problems i n a c h i e v i n g adequate experimental s t u d i e s and outcomes on p e r t i n e n t t o p i c s . Large l o t s of land were needed f o r experimentation, and, as t h i s was not p o s s i b l e , smaller l o t s were used f o r s e v e r a l s i m i l a r s t u d i e s . There were a l s o d i f f i c u l t i e s i n mai n t a i n i n g the same environmental v a r i a b l e s and agronomic p r a c t i c e s when attempting t o gather i n f o r m a t i o n on i d e n t i c a l a g r i c u l t u r a l questions. The researchers thus had to f i n d a way i n which to i n t e r p r e t the l a r g e body of s i n g l e study designs, viewing s i m i l a r questions w i t h d i f f e r i n g r e s u l t s (Bangert-Drowns, 1986). At f i r s t the s t a t i s t i c a l problem (at l e a s t i n s i m i l a r cases) might appear to be s i m i l a r t o that of the a n a l y s i s of a s i n g l e r e p l i c a t e d t r i a l , however the s i t u a t i o n was u s u a l l y 38 more complex, and the u n c r i t i c a l a p p l i c a t i o n of methods appropriate to s i n g l e experiments may have l e d to erroneous co n c l u s i o n s . Therefore researchers sought to modify the ordi n a r y a n a l y s i s of variance i n order t o f i n d the general u n d e r l y i n g p r i n c i p l e s and patterns of s e v e r a l d i f f e r e n t r e s u l t s (Yates et a l . , 1938). In 1931 T i p p i t answered the problem by suggesting methods to t e s t the s t a t i s t i c a l s i g n i f i c a n c e of r e s u l t s combined from separate experiments. Researchers, such as F i s h e r (1932), K. Pearson (1933), and E. S. Pearson (1938), a l s o sought ways to combine p r o b a b i l i t y values from t e s t s of s i g n i f i c a n c e . Yates and Cochran (1938) developed methods to estimate the mean e f f e c t and v a r i a b i l i t y of a s p e c i f i c treatment s t u d i e d at va r i o u s a g r i c u l t u r a l centers. W i l kinson (1951) suggested a method of using the "meta-analytic" a t t i t u d e of a g r i c u l t u r a l research f o r the s o c i a l s c iences. He proposed that the binomial d i s t r i b u t i o n c o uld be used t o determine the expected number of s i g n i f i c a n t r e s u l t s given a tr u e n u l l hypothesis since study r e s u l t s are e i t h e r s i g n i f i c a n t or n o n s i g n i f i c a n t . The i n v e s t i g a t i o n of methods f o r i n t e r g r a t i n g r e s u l t s from d i f f e r e n t s t u d i e s continued and i n the seventies at l e a s t four i n v e s t i g a t o r s had worked independently on complementary e f f o r t s to r e s o l v e the issue of combining r e s u l t s from, d i f f e r e n t s t u d i e s . Schmidt, Hunter, and colleagues (1973, 1976, 1978) examined c r i t e r i o n v a l i d i t y f o r s e v e r a l small sample independent s t u d i e s using the same or s i m i l a r measures. Rosenthal (1978) researched methods of aggregating r e s u l t s of independent s t u d i e s by combining t h e i r p r o b a b i l i t y values. Glass (1976) proposed a s t a t i s t i c a l a n a l y s i s u s i n g e f f e c t s i z e (a common value f o r each e m p i r i c a l study) to examine the summary f i n d i n g s of each study. This became commonly known as meta-analysis. Advantages of Meta-analysis Meta-analysis has two major advantages over other i n t e r g r a t i v e reviews. F i r s t , i t provides a set of procedures f o r decision-making during a l i t e r a t u r e review, and second, i t a p p l i e s s t a t i s t i c s to q u a n t i t a t i v e r e p r e s e n t a t i o n s of study outcomes.. The set of procedures f o r doing meta-analysis are analogous to those conducted i n any primary research and i n c l u d e s ; the s e l e c t i o n of questions or hypotheses, d e f i n i t i o n and measurement of the v a r i a b l e s being considered, sampling, data a n a l y s i s , and r e p o r t i n g / d i s c u s s i n g the r e s u l t s . The sampling i n meta-analysis may be l e s s prejudgemental than other reviews, i n that a p r i o r i opinion on the q u a l i t y of research methodologies i s not necessary. For inst a n c e , i t does not d i s q u a l i f y d i s s e r t a t i o n s because they have not been pu b l i s h e d . Meta-analysis considers the question of methodological weaknesses i n the sample s t u d i e s and t h e i r r e l a t i o n s h i p to study r e s u l t s as an p o s t e r i o r i question (Glass et a l . , 1981). The data a n a l y s i s and r e p o r t i n g p a r t of the 40 r e v i e w , seeks t o p r o v i d e u s e f u l g e n e r a l c o n c l u s i o n s from t h e e x a m i n a t i o n o f d i f f e r e n t s t u d i e s c o n c e r n e d about a s i m i l a r p roblem. The s m a l l d i f f e r e n c e s which o c c u r w i t h i n t h e s t u d i e s under r e v i e w a r e i g n o r e d i n t h e p r o c e s s o f making g e n e r a l i z a t i o n s about t h e o v e r a l l p a t t e r n s found w i t h i n t h o s e s t u d i e s . Thus t h e g e n e r a l c o n c l u s i o n s can g i v e p r a c t i c a l i n f o r m a t i o n about t h e u t i l i t y o f c e r t a i n t r e a t m e n t s . The i n t e r a c t i o n s o c c u r i n g w i t h i n each i n d i v i d u a l s t u d y might a l s o be acknowledged i n t h e c o n c l u d i n g remarks o f t h e r e v i e w , s h o u l d t h e r e v i e w e r t h i n k i t p e r t i n e n t t o t h e t o p i c under e x a m i n a t i o n . M e t a - a n a l y s i s i s q u a n t i t a t i v e i n t h a t i t uses s t a t i s t i c a l methods f o r e x t r a c t i n g and o r g a n i z i n g i n f o r m a t i o n o b t a i n e d from a l a r g e s a m p l i n g of s t u d i e s . T a b l e 1 p r o v i d e s a summary o f t h e p r o c e d u r a l s t e p s s u g g e s t e d by G l a s s (1976) and G l a s s e t a l . (1981) . When t h e s e s t e p s a re m e t i c u l o u s l y f o l l o w e d , o t h e r r e s e a r c h e r s c o u l d d u p l i c a t e t h e s t e p s i n o r d e r t o check o r v e r i f y t h e r e s u l t s o f t h e m e t a - a n a l y s i s . The r e p l i c a b l e n a t u r e o f t h i s s y s t e m a t i c approach makes t h e m e t a - a n a l y t i c r e v i e w t h e c l o s e s t p o s s i b l e t o a w e l l d e s i g n e d o r i g i n a l e x p e r i m e n t a l r e s e a r c h . L i m i t a t i o n s o f M e t a - a n a l y s i s A l l a n a l y t i c approaches t o i n t e g r a t i v e r e v i e w s have d i f f i c u l t i e s i n t h e a p p l i c a t i o n o f t h e approach and m e t a - a n a l y s i s i s no e x c e p t i o n . The d i f f i c u l t i e s o f t h e m e t a - a n a l y t i c approach are as follows: 41 Table 1 P r o c e d u r a l steps i n meta-Analysis 1. I d e n t i f i c a t i o n of the problem 2. L i t e r a t u r e search - thoroughness of s e arch and b a s i s f o r i n c l u s i o n or e x c l u s i o n of s t u d i e s 3. Coding the c h a r a c t e r i s t i c s of each study 4. Q u a n t i f y i n g study f i n d i n g s - e f f e c t s i z e c a l c u l a t i o n 5. S t a t i s t i c a l a n a l y s i s of e f f e c t s i z e data 6. I n t e r p r e t a t i o n of r e s u l t s 7. R e p o r t i n g steps 1 through 6 i n a review paper. 42 (a) I t c a n n o t a s s e s s e v i d e n c e w h i c h d o e s n o t d i r e c t l y p e r t a i n t o a g i v e n t o p i c . When t h e t o p i c u n d e r i n v e s t i g a t i o n h a s b e e n i n d i r e c t l y s t u d i e d , t h e e v i d e n c e c a n n o t be woven t o g e t h e r w i t h o t h e r s t u d y r e s u l t s . F o r i n s t a n c e , i f t h e t o p i c i s "Does t r e a t m e n t Y l e s s e n t h e e f f e c t s o f s t r e s s i n s t r e s s e d a d u l t s ? " T h e r e may n o t be s t u d i e s d i r e c t l y e x a m i n i n g t h i s q u e s t i o n , b u t t h e r e may be s t u d i e s on t h e e f f e c t s o f Y on s t r e s s i n m i c e . The l a t t e r i n f o r m a t i o n c a n n o t be woven t o g e t h e r w i t h t h e e f f e c t s o f Y on s t r e s s i n humans. The m e t a - a n a l y t i c a p p r o a c h c a n be u s e d t o e v a l u a t e t h e r e s u l t s w i t h i n e a c h s e t o f s t u d i e s c o n c e r n i n g t h e t r e a t m e n t Y i n s t r e s s e d humans o n l y . (b) E a c h p r i m a r y s t u d y i n c l u d e d i n t h e m e t a - a n a l y s i s m i g h t u s e d i f f e r e n t i n s t r u m e n t s t o m e a s u r e t h e d e p e n d e n t v a r i a b l e s . The c o n s t r u c t s o f t h e d e p e n d e n t v a r i a b l e s may be d i f f e r e n t e v e n t h o u g h t h e y a r e u s e d u n d e r a s i n g l e t o p i c . F o r i n s t a n c e , t h e o u t c o m e s o f v a r i o u s s t u d i e s on t h e e f f e c t s o f e x e r c i s e on s t r e s s c o u l d i n c l u d e a n x i e t y , t e n s i o n , d e p r e s s i o n , c o p i n g a b i l i t i e s , a n d b i o c h e m i c a l l e v e l s . E a c h o f t h e s e d e p e n d e n t v a r i a b l e s w i l l be m e a s u r e d by a d i f f e r e n t m e t r i c i n s t r u m e n t . T h e r e a r e a l s o d i f f e r e n t i n s t r u m e n t s t o m e a s u r e t h e same d e p e n d e n t v a r i a b l e . T h e s e c o n c e r n s a r e p a r t o f t h e c o n t r o v e r s i a l " a p p l e s a n d 43 o r a n g e s " a r g u m e n t a g a i n s t t h e G l a s s i a n m e t a - a n a l y t i c a p p r o a c h . G l a s s ' r e b u t t a l t o t h e s e c o n c e r n s s t a t e s t h a t t h e r e i s no n e e d t o c o m p a r e s t u d i e s t h a t a r e t h e same b e c a u s e t h e f i n d i n g s w o u l d be s i m i l a r , w i t h i n s t a t i s t i c a l e r r o r . The p u r p o s e o f t h e m e t a - a n a l y t i c a p p r o a c h i s t o f i n d t h e p a t t e r n s w i t h i n d i f f e r e n t s t u d i e s on t h e same t o p i c . He f u r t h e r a r g u e s t h a t p o o l i n g t h e f i n d i n g s o f s t u d i e s 1 t h r o u g h ' 10 i s s i m i l a r t o p o o l i n g o f r e s u l t s f r o m p e r s o n s 1 t h r o u g h 50 i n a s i n g l e r e s e a r c h e x p e r i m e n t a s t h e s u b j e c t s a r e a s d i f f e r e n t a n d a s much a l i k e f r o m e a c h o t h e r a s s t u d i e s a r e d i f f e r e n t f r o m e a c h o t h e r ( G l a s s e t a l . , 1 9 8 1 ) . (c) I t c a n n o t be u s e d t o i n f e r w h i c h v a r i a b l e s w i t h i n e a c h s t u d y , on a g i v e n t o p i c , c a u s e d t h e d i f f e r i n g r e s u l t s . E v e n when a l l t h e s t u d i e s w i t h i n t h e r e v i e w h a v e u s e d g o o d e x p e r i m e n t a l d e s i g n s , t h e v a r i a b l e s i d e n t i f i e d f r o m t h e s t u d i e s c a n n o t be s y s t e m a t i c a l l y m a n i p u l a t e d a s i n a p r i m a r y e x p e r i m e n t . (d) T h e r e a r e no c l e a r l y d o c u m e n t e d s t a n d a r d s f o r s a m p l e s i z e s when u s i n g s t a t i s t i c s f o r t h e m e t a - a n a l y s i s . S i m i l a r l y t o p r i m a r y r e s e a r c h , t h e m e t a - a n a l y s i s n e e d s a l a r g e s a m p l e s i z e i f m u l t i v a r i a t e s t a t i s t i c s a r e t o be u s e d . H o w e v e r t h e n u m b e r o f c a s e s may be g r e a t e r t h a n t h e number o f s t u d i e s b e i n g r e v i e w e d b e c a u s e G l a s s s u g g e s t e d u s i n g an " e f f e c t " a s t h e u n i t o f a n a l y s i s a n d e a c h s t u d y may h a v e more t h a n 44 one e f f e c t . "An e f f e c t i s d e f i n e d as any a n a l y s i s W i t h i n a st u d y o f a g i v e n t r e a t m e n t and outcome a t a g i v e n t i m e o f measurement" ( J a c k s o n , 1980, p. 453). Each s t u d y c o u l d have s e v e r a l a n a l y s i s o f a g i v e n t r e a t m e n t and i t s outcomes, (e) There may be d i f f i c u l t i e s a c h i e v i n g v a l i d and r e l i a b l e c o d i n g o f t h e c h a r a c t e r i s t i c s o f t h e p r i m a r y s t u d i e s t o b e . a n a l y z e d . T h i s p r oblem i s not g r e a t i f t h e s e t o f s t u d i e s t o be coded i s r e l a t i v e l y s m a l l and can be done by a s i n g l e i n v e s t i g a t o r . There i s a l s o a s e l e c t i o n b i a s ' not o n l y b.y t h e coder but by t h e p r i m a r y r e s e a r c h e r as t h e r e tends t o be s y s t e m a t i c d i f f e r e n c e s among r e s u l t s o f r e s e a r c h a p p e a r i n g i n a p a r t i c u l a r t y p e o f j o u r n a l v s . t h e s e s v s . books. G l a s s views t h e s e d i f f i c u l t i e s as p a r t o f t h e d i f f e r e n c e s which o c c u r i n r e s e a r c h d e s i g n s o f a l l q u a l i t i e s . Each s t u d y can have i t s own p a r t i c u l a r weakness ( i . e . , weak i n measurement but o t h e r w i s e s t r o n g ; weak o n l y i n i n t e r n a l v a l i d i t y o r d a t a a n a l y s i s . Summary The m e t a - a n a l y t i c approach g u i d e s t h e r e s e a r c h e r ' s d e c i s i o n making p r o c e s s e s i n q u a n t i t a t i v e l y i n t e g r a t i n g t h e s t u d i e s ' r e s u l t s . In a r e a s of st u d y where t h e r e has been c o n s i d e r a b l e r e s e a r c h , but c o n f l i c t i n g f i n d i n g s , m e t a - a n a l y s i s i s a s u i t a b l e r e s e a r c h p r o c e d u r e t o use t o attempt t o i d e n t i f y 45 the v a r i a b l e s which may cause the ambiquity. E x e r c i s e and s t r e s s i s such an area, t h e r e f o r e meta-analysis i s an appropriate approach. Method L i t e r a t u r e S e a r c h The l i t e r a t u r e s e a r c h i n c l u d e d a c o m p u t e r i z e d s e a r c h o f P s y c h o l o g i c a l A b s t r a c t s , M e d l i n e , M e d l a r s , E r i c Index, D i s s e r t a t i o n s A b s t r a c t I n t e r n a t i o n a l and a manual s e a r c h o f t h e Oregon M i c r o f i c h e L i s t . The r e f e r e n c e s i n r e l e v a n t r e s e a r c h were used i n t r a c i n g a d d i t i o n a l m a t e r i a l . Only s t u d i e s on a d u l t s o f b o t h sexes, aged 18 and over, i n t h e a r e a of ^ e f f e c t s o f e x e r c i s e on s t r e s s / a n x i e t y ' were s e a r c h e d f o r . The s t u d i e s t h a t were i n c l u d e d i n t h e r e v i e w were e i t h e r e x p e r i m e n t a l / o r q u a s i - e x p e r i m e n t a l , and used a v a l i d a t e d s e l f -r e p o r t measure o f t h e s t a t e / t r a i t c o n s t r u c t o f a n x i e t y . The v a l i d a t e d s e l f - r e p o r t measures were i n s t r u m e n t s which had been f r e q u e n t l y used t o measure a n x i e t y , p o s s e s s e d f a c e and c o n s t r u c t v a l i d i t y and t e s t - r e t e s t r e l i a b i l i t y . The i n s t r u m e n t s used t o measure a n x i e t y i n t h e s t u d i e s i n c l u d e d i n th e m e t a - a n a l y s i s were t h e : POMS, STAI, M u l t i p l e A d j e c t i v e C h e c k l i s t (MAACL), MMPI ( s c a l e #7), T a y l o r M a n i f e s t A n x i e t y S c a l e ( T a y l o r , 1953) and Test A n x i e t y (Sarason, 1972). The POMS and STAI were used i n 19 o f t h e 24 s t u d i e s i n t h e meta-a n a l y s i s . A n o t h e r c r i t e r i a f o r i n c l u s i o n r e l a t e d t o t h e t y p e of e x e r c i s e p r o g r a m — a n e x e r c i s e program had t o i n v o l v e a ' r e c o g n i z e d f i t n e s s p r e s c r i p t i o n ( S t e w a r t , 1982) over a p e r i o d o f a t l e a s t 4-weeks. S t u d i e s t h a t (a) examined t h e e f f e c t s o f one bout o f e x e r c i s e , (b) i n c l u d e d o n l y p h y s i o l o g i c a l measures of s t r e s s , (c) a s s e s s e d i n d i v i d u a l s o f d i f f e r i n g f i t n e s s 47 l e v e l s a n d t h e n r e s p o n s e s t o s t r e s s , o r (d) i n v e s t i g a t e d p s y c h i a t r i c p o p u l a t i o n s , were e x c l u d e d . O f t h e 61 s t u d i e s i d e n t i f i e d t h a t e x a m i n e d t h e e f f e c t s o f e x e r c i s e on s t r e s s , o n l y 24 met t h e c r i t e r i a f o r i n c l u s i o n . T h r e e d i s s e r t a t i o n s c o u l d n o t be o b t a i n e d . O t h e r s t u d i e s were e x c l u d e d b e c a u s e t h e y d i d n o t meet t h e f o l l o w i n g c r i t e r i a : (a) 7 were o f a s i n g l e s e s s i o n d e s i g n , (b) 2 e x a m i n e d a p s y c h i a t r i c p o p u l a t i o n , (c) 2 were i n v e s t i g a t i n g t h e e f f e c t s o f e x e r c i s e on a d o l e s c e n t s , (d) 3 e x a m i n e d t h e e f f e c t s o f e x e r c i s e u s i n g a p r o c e d u r e w h i c h was s i m i l a r t o a s i n g l e s e s s i o n d e s i g n , (e) 6 i n v e s t i g a t e d t h e e f f e c t s o f e x e r c i s e on t y p e A p e r s o n a l i t i e s , ( f ) 7 e x a m i n e d f i t a n d u n f i t p a r t i c i p a n t s ' p h y s i o l o g i c a l a n d p s y c h o l o g i c a l r e s p o n s e s t o s t r e s s o r s , a n d (g) 7 i n v e s t i g a t e d t h e p h y s i o l o g i c a l a n d p s y c h o l o g i c a l r e s p o n s e s o f p a r t i c i p a n t s p r e a n d p o s t a s t r e s s e v e n t . See A p p e n d i x A f o r a l i s t o f t h e s t u d i e s t h a t were i n c l u d e d . D e s i g n a n d P r o c e d u r e s The n e x t s t e p i n v o l v e d i d e n t i f y i n g a n d c o d i n g t h e p o t e n t i a l l y i m p o r t a n t p a r a m e t e r s o f t h e m e t a - a n a l y s i s . The v a r i a b l e s t h a t c o u l d i n f l u e n c e t h e v a r i a n c e i n s t u d y o u t c o m e s were i d e n t i f i e d a n d c o d e d s o t h a t t h e s e v a r i a b l e s c o u l d be c o n s i d e r e d i n a n a l y s i n g t h e e f f e c t d a t a . The 24 s t u d i e s y i e l d e d 61 e f f e c t s i z e s . In f u r t h e r d i s c u s s i o n o f t h e v a r i a b l e s i n c l u d e d i n t h e m e t a - a n a l y s i s , t h e e f f e c t s i z e s w i l l b e t h e N f o r e a c h v a r i a b l e l e v e l . 48 Study type. Whether the research study was pu b l i s h e d or unpublished was noted as some meta-analytic researchers consider t h i s t o be a f a c t o r i n the q u a l i t y of the research. There were 40 pub l i s h e d study e f f e c t s i z e s and 21 unpublished study e f f e c t s i z e s . Design. The type of design used i n the study was coded as within-group change (e.g., pre- t o post-design; N = 33) and cont r a s t change (e.g., between groups design; N = 28). Gender. The p a r t i c i p a n t s sex was noted as i t could i n f l u e n c e the anxiety response to the e x e r c i s e treatment. Studies were coded as a l l female (N = 15), a l l - male (N = 4) and both (N = 42) .. Composition of sample. The type of p o p u l a t i o n the p a r t i c i p a n t s represent (e.g., student or non-student population) could a l s o be a f a c t o r i n t h e i r s t r e s s r e d u c t i o n a f t e r p a r t i c i p a t i n g i n an e x e r c i s e treatment program. Therefore, s t u d i e s were coded as students (N = 22), students and f a c u l t y (N = 2) and non-students (N = 37). Stress l e v e l . The s t r e s s l e v e l was i n t e g r a l to t h i s study as i t was i n v e s t i g a t i n g whether e x e r c i s e was more e f f e c t i v e f o r greater s t r e s s e d or l e s s s t r e s s e d people. There i s some i n d i c a t i o n that s t r e s s l e v e l may i n f l u e n c e the anxie t y response t o the e x e r c i s e i n t e r v e n t i o n , t h e r e f o r e s t u d i e s were coded as minimally s t r e s s e d (N = 37) and s t r e s s e d (N = 24). The s t u d i e s of s t r e s s e d people, a d v e r t i s e d f o r people who f e l t s t r e s s e d and had s p e c i f i c c r i t e r i a f o r s t r e s s l e v e l s . While 49 minimally s t r e s s e d people were determined because they d i d not report a n x i e t y p r i o r to e n t e r i n g the research study. P s y c h o l o g i c a l measure. The instruments used t o measure s t a t e or t r a i t a nxiety (dependent v a r i a b l e s ) were coded as t r a i t (N = 32) and s t a t e (N = 29) anxi e t y . The t e n s i o n category of the POMS, the s t a t e subscale of STAI, MAACL, and Test Anxiety were coded as s t a t e anxiety. The t r a i t subscale of STAI, and the #7 subscale of the MMPI were coded as t r a i t a n x iety. Program length . The length of the e x e r c i s e i n t e r v e n t i o n was coded as 6- to 8-weeks (N = 18), 8- to 12-weeks (N = 29), and 12 plus weeks (N = 14). The length of an i n t e r v e n t i o n has been known t o play a part i n p s y c h o l o g i c a l treatment programs. Type of e x e r c i s e treatment. Whether the type of e x e r c i s e had an e f f e c t on people's s t r e s s l e v e l s was one of the research questions examined. The types of e x e r c i s e were t h e r e f o r e coded as aerobic (N = 54), non-aerobic (N = 2), aerobic and weights (N = 3), and aerobic and c o u n s e l l i n g (N = 2) . Frequency of e x e r c i s e s e s s i o n . The number of times the p a r t i c i p a n t s e x e r c i s e d each week was coded as 3 times per week (N = 50) and 3 or more times per week (N = 11). Leaders. The type of le a d e r s h i p f o r each e x e r c i s e i n t e r v e n t i o n and the q u a l i f i c a t i o n s of the leaders were noted. This i n f o r m a t i o n was coded as t r a i n e d (N = 33), no t r a i n i n g (N = 1), l e a d e r l e s s (N = 8), and not s p e c i f i e d (N = 19). The 50 ma j o r i t y of t r a i n e d leaders were t r a i n e d i n e x e r c i s e management (N = 21) and 3 st u d i e s (N = 12) mentioned p s y c h o l o g i c a l t r a i n i n g as w e l l as e x e r c i s e management t r a i n i n g of the le a d e r s . A t t r i t i o n r a t e . The drop-out ra t e was coded as greater than 20% (N = 13), l e s s than 20% (N = 23), and not mentioned (N = 25). The drop-out r a t e from an e x e r c i s e i n t e r v e n t i o n could i n f l u e n c e the e f f e c t of e x e r c i s e on s t r e s s l e v e l . Follow-up. Whether „or not the s t u d i e s i n c l u d e d some form of follow-up assessment was coded as Yes (N = 18) or No (N = 43). Follow-up i s one way of not i n g whether the b e n e f i t s of an ex e r c i s e program has continued a f t e r completion of program. D e s c r i p t i v e s t a t i s t i c s i n c l u d i n g means and standard d e v i a t i o n s f o r the dependent v a r i a b l e s (pre/post scores) or the t e s t s t a t i s t i c s t and F values and t h e i r degrees of freedom were noted. Once a l l the necessary inform a t i o n was gathered, the best method to e x t r a c t comparable s t a t i s t i c a l i n f o r m a t i o n from a l l the s t u d i e s under review was decided upon. Not a l l the st u d i e s contained the means and standard d e v i a t i o n s f o r the experimental and c o n t r o l groups from which one could d i r e c t l y compute the e f f e c t s i z e . The st u d i e s t h a t d i d not have the l a t t e r i n f o r m a t i o n but d i d have a t or F value were subjected to a l t e r n a t i v e procedures i n order t o convert i n t o e f f e c t s i z e s . One or more e f f e c t s i z e ( s ) were c a l c u l a t e d from the 51 d e s c r i p t i v e s t a t i s t i c s or the t e s t s t a t i s t i c s . The e f f e c t s i z e s were i n t u r n s t a t i s t i c a l l y analyzed ( a n a l y s i s of va r i a n c e ) , using the coded v a r i a b l e s as independent v a r i a b l e s and the e f f e c t s i z e s as the dependent v a r i a b l e . The d e t a i l s of the c a l c u l a t i o n of e f f e c t s i z e s and the a n a l y s i s of e f f e c t s i z e s are discussed under the headings of c a l c u l a t i o n of e f f e c t s i z e s and a n a l y s i s of data. Some of the s t u d i e s used a pre- to post-treatment design, and examined the e f f e c t of an ex e r c i s e program on a s i n g l e group. The e f f e c t s i z e could t h e r e f o r e only be c a l c u l a t e d f o r a w i t h i n group change/difference. Other s t u d i e s examined the d i f f e r e n c e from pre- to post-treatment f o r both a treatment and a c o n t r o l group. This permitted the c a l c u l a t i o n of the d i f f e r e n c e between two groups i n the pre- to post-change. The l a t t e r d i f f e r e n c e was c a l l e d the con t r a s t change f o r the purposes of c a l c u l a t i n g an e f f e c t s i z e . Some stu d i e s provided the d e s c r i p t i v e s t a t i s t i c s so that the w i t h i n group change could be c a l c u l a t e d even though the.study only i n v e s t i g a t e d the con t r a s t change. Studies that i n v e s t i g a t e d the d i f f e r e n c e ( i n pre- to post-change) between an experimental group and a c o n t r o l group, or between two or more a l t e r n a t i v e treatments (one being exercise) f o r s t r e s s , were defined as c o n t r a s t change s t u d i e s . C a l c u l a t i o n of E f f e c t Sizes Within group change. The stu d i e s that were a pre/post design of a s i n g l e treatment group and reported mean and 52 s t a n d a r d d e v i a t i o n s c o r e s were s u b j e c t e d t o a m o d i f i e d G l a s s i a n (1977) m e t h o d o f c a l c u l a t i n g t h e e f f e c t s i z e . T r a d i t i o n a l l y t h e e f f e c t s i z e i s o b t a i n e d when t h e d i f f e r e n c e b e t w e e n t h e means o f t h e e x p e r i m e n t a l g r o u p a n d t h e c o n t r o l g r o u p i s d i v i d e d b y t h e c o n t r o l g r o u p ' s s t a n d a r d d e v i a t i o n . H e d g e s (1981) p r o p o s e d t h a t a p o o l e d e s t i m a t e o f t h e v a r i a n c e p r o v i d e s a more p r e c i s e e s t i m a t e o f t h e p o p u l a t i o n v a r i a n c e r a t h e r t h a n t h e c o n t r o l g r o u p s t a n d a r d d e v i a t i o n , b e c a u s e i n most c a s e s t h e g r o u p v a r i a n c e i s h o m o g e n o u s . T h e r e f o r e , i n t h e p r e / p o s t d e s i g n t h e d i f f e r e n c e b e t w e e n t h e p o s t - m e a n s c o r e a n d t h e p r e - m e a n s c o r e was d i v i d e d b y t h e p o o l e d s t a n d a r d d e v i a t i o n o f t h e p r e - a n d p o s t - s t a n d a r d d e v i a t i o n s . T h i s g i v e s t h e e f f e c t s i z e o f t h e c h a n g e o c c u r r i n g w i t h i n t h e e x p e r i m e n t a l g r o u p o n l y . The e q u a t i o n i s : Af. -Af, ES - 1 2 where the: M1 - pretest mean M2 - post test mean Sp - average standard deviation One s t u d y w i t h a p r e / p o s t d e s i g n d i d n o t r e p o r t d e s c r i p t i v e s t a t i s t i c s b u t d i d g i v e t h e t v a l u e c a l c u l a t e d . The f o l l o w i n g e q u a t i o n was u s e d t o c a l c u l a t e t h e e f f e c t s i z e ( R o s e n t h a l & R o s n o w , 1984 , p . 2 3 6 ) . ES - t 53 Contrast change. The st u d i e s t h a t had examined the d i f f e r e n c e s between two.groups, an e x e r c i s e group and e i t h e r a c o n t r o l group or an a l t e r n a t i v e treatment f o r s t r e s s , had a cont r a s t change design. The con t r a s t change i s the d i f f e r e n c e between the experimental group's pre- to post-means and the c o n t r o l group's pre- to post-means d i v i d e d by the pooled standard d e v i a t i o n . The c o n t r a s t change e f f e c t s i z e was c a l c u l a t e d as f o l l o w s : where Mx - experimental pretest mean M2 - experimental p o s t t e s t mean M3 - control pretest mean Mi - control post test mean The standard d e v i a t i o n i s the square root of the weighted pooled variance (Thomas & French, 1986). The equation i s : SP (Nx - 1 ) 5 / + (N2 -DSJ \ N1 + N2 - 2 Some s t u d i e s d i d not report the d e s c r i p t i v e s t a t i s t i c s but d i d give the t e s t s t a t i s t i c s . Therefore, the t or F value had t o be used i n order t o estimate the e f f e c t s i z e of the experimental group or the con t r a s t change (Wolf, 1986, p. 35) . The e f f e c t s i z e equation f o r the con t r a s t when the t s t a t i s t i c i s r eported i s : 54 ES - -2JL The e f f e c t s i z e e q u a t i o n f o r s t u d i e s r e p o r t i n g t h e d i f f e r e n c e s b e t w e e n g r o u p s u s i n g F i s : ES -A l t h o u g h t h e s e e q u a t i o n s were u s e d f o r most o f t h e s t u d i e s i n c l u d e d i n t h e m e t a - a n l y s i s , t h e r e were two e x c e p t i o n s . M o s e s e t a l . (1989) t r a n s f o r m e d t h e t e n s i o n / a n x i e t y s c o r e s on t h e POMS t o mean, l o g s c o r e s . U s i n g an a n t i - l o g t a b l e , t h e mean l o g s c o r e s o f t h e m o d e r a t e f i t g r o u p a n d t h e c o l l a p s e d s c o r e s o f t h e a t t e n t i o n - p l a c e b o a n d w a i t l i s t g r o u p s were t r a n s f o r m e d t o t h e mean POMS s c o r e s . T h i s s t u d y a n d D o r i n s k y ' s (1984) s t u d y d i d n o t h a v e t h e s t a n d a r d d e v i a t i o n s o f t h e means f o r t h e POMS s c o r e s . A n e s t i m a t i o n o f t h e s t a n d a r d d e v i a t i o n s f o r t h e s e s t u d i e s were d e r i v e d b y a v e r a g i n g t h e s t a n d a r d d e v i a t i o n s o f o t h e r s t u d i e s u s i n g t h e POMS m e a s u r e . D a t a A n a l y s i s . D e s c r i p t i v e s t a t i s t i c s o f a l l v a r i a b l e s t h o u g h t t o i n f l u e n c e t h e e f f e c t s i z e were c o m p u t e d u s i n g t h e BMD P2D p r o g r a m ( D i x o n , 1 9 8 5 ) . F r e q u e n c y t a b l e s u s i n g t h e BMD P 4 F p r o g r a m were c o m p u t e d t o c h e c k f o r f r e q u e n c y c o u n t s o f t h e v a l u e s g i v e n t o name t h e c a t e g o r i e s w i t h i n e a c h v a r i a b l e u s e d ( i . e . , d e s i g n : 1 = w i t h i n g r o u p c h a n g e , 2 = c o n t r a s t c h a n g e ) . 55 T h i s was n e e d e d t o d e t e r m i n e i f t h e d i s t r i b u t i o n s w o u l d p e r m i t g r o u p i n g f o r a n a l y s i s o f v a r i a n c e . S e v e r a l o n e - w a y a n d t w o - w a y ANOVAS were c o m p u t e d u s i n g t h e BMD P2V p r o g r a m . O n e - w a y a n a l y s i s o f v a r i a n c e h e l p e d t o d e c i d e w h i c h i n d e p e n d e n t v a r i a b l e s m i g h t be s i g n i f i c a n t a n d h a v e an i n f l u e n c e i n c o m b i n a t i o n w i t h a n o t h e r v a r i a b l e i n s h e d d i n g l i g h t on t h e e f f e c t s o f e x e r c i s e on s t r e s s . Two-way ANOVAS were c o m p u t e d i n o r d e r t o a s s i s t i n a n s w e r i n g t h e q u e s t i o n s p o s e d b y t h i s s t u d y . The i n d e p e n d e n t v a r i a b l e s were d e s i g n t y p e , s t r e s s l e v e l , t y p e o f e x e r c i s e p r o g r a m , p r o g r a m l e n g t h , f r e q u e n c y o f p r o g r a m , l e a d e r s , a t t r i t i o n r a t e , p s y c h o l o g i c a l m e a s u r e s , c o m p o s i t i o n o f s a m p l e , g e n d e r , s t u d y t y p e , a n d f o l l o w - u p . The d e p e n d e n t v a r i a b l e was e f f e c t s i z e . R e s u l t s The 2 4 s t u d i e s i n c l u d e d i n t h e m e t a - a n a l y s i s p r o v i d e d 61 e f f e c t s i z e s r a n g i n g i n m a g n i t u d e f r o m a min imum v a l u e o f -0.14 t o a maximum v a l u e o f 2.02. The mean e f f e c t s i z e o v e r a l l s t u d i e s was 0.57. The e f f e c t s i z e c o n v e y s t h e m a g n i t u d e o f t h e d i f f e r e n c e s c o r e s a n d b a s e d on C o h e n ' s (1988) c a t e g o r i z a t i o n , i t c a n b e c o n s i d e r e d t o be o f " m o d e r a t e " s i z e . A t e s t o f t h e h y p o t h e s i s t h a t t h e mean e f f e c t s i z e was d i f f e r e n t f r o m z e r o was s i g n i f i c a n t (F ( l,60) = 21.17, p<.001). T h e r e f o r e , t h e r e s u l t , i n d i c a t e s t h a t , a v e r a g e d o v e r a l l s t u d i e s a n d c o n d i t i o n s , e x e r c i s e i s an e f f e c t i v e s t r e s s r e d u c e r . S e l e c t i o n o f I n d e p e n d e n t V a r i a b l e s f o r ANOVAS Two-way ANOVAS were c o n d u c t e d t o e x a m i n e t h e e f f e c t o f s e l e c t e d i n d e p e n d e n t v a r i a b l e s on t h e d e p e n d e n t v a r i a b l e a n x i e t y . T h e f o l l o w i n g i n d e p e n d e n t v a r i a b l e s c o n t a i n e d l e v e l s w i t h s u f f i c i e n t c e l l s i z e s t o p e r m i t a t w o - w a y a n a l y s i s : d e s i g n t y p e , s t r e s s l e v e l , s t u d y t y p e , p r o g r a m l e n g t h , a n d p s y c h o l o g i c a l m e a s u r e . O n e - w a y ANOVAS were c o n d u c t e d f o r t h o s e i n d e p e n d e n t v a r i a b l e s w h i c h , when c r o s s e d w i t h a n o t h e r v a r i a b l e i n o r d e r t o p e r f o r m a t w o - w a y f a c t o r i a l ANOVA, y i e l d e d c e l l s i z e s o f l e s s t h a n f i v e . T r e a t m e n t E f f e c t s D e s i g n . A t w o - w a y ( d e s i g n b y s t r e s s l e v e l ) ANOVA was p e r f o r m e d i n o r d e r t o a s c e r t a i n w h e t h e r t h e r e was a d i f f e r e n c e b e t w e e n t h e t y p e o f d e s i g n ( w i t h i n g r o u p c h a n g e a n d c o n t r a s t c h a n g e ) a n d t h e s t r e s s l e v e l ( m i n i m a l l y s t r e s s e d a n d s t r e s s e d T A B L E 2 The mean a n d s t a n d a r d d e v i a t i o n e f f e c t s i z e s o f i n d e p e n d e n t  v a r i a b l e s I n d e p e n d e n t V a r i a b l e s N E f f e c t Mean S i z e s SD D e s i g n w i t h i n g r o u p c h a n g e c o n t r a s t c h a n g e S t r e s s l e v e l min imum s t r e s s s t r e s s e d P s y c h o l o g i c a l m e a s u r e s t a t e a n x i e t y t r a i t a n x i e t y S t u d y t y p e p u b l i s h e d u n p u b l i s h e d P r o g r a m l e n g t h 6 - t o 8 - w e e k s 8 - t o 1 2 - w e e k s 12 p l u s weeks F r e q u e n c y o f p r o g r a m 3 t i m e s p e r week 3 p l u s t i m e s p e r week G e n d e r M a l e F e m a l e B o t h s e x e s A t t r i t i o n r a t e G r e a t e r t h a n 20% L e s s t h a n 20% N o t m e n t i o n e d L e a d e r s T r a i n e d T r a i n i n g n o t s p e c i f i e d No l e a d e r s F o l l o w - u p Y e s No 33 28 37 24 29 32 40 21 18 29 14 50 11 4 15 42 13 23 25 33 20 18 43 54 60 43 78 45 67 44 82 55 69 32 . 60 .42 ,44 ,34 , 66 , 42 , 65 ,57 .57 .54 . 60 57 57 47 47 37 54 38 52 ,33 ,58 , 36 ,52 ,41 ,50 .27 ,34 ,41 , 47 .29 . 62 .38 .54 . 43 .24 .29 .53 58 TABLE 2 The mean and standard d e v i a t i o n e f f e c t s i z e s of independent  v a r i a b l e s Independent V a r i a b l e s N E f f e c t Sizes Mean SD Type of E x e r c i s e Aerobic 54 .51 .41 Non-aerobic 2 .46 .12 Aerobics & weights 3 .69 .15 Aerobics & c o u n s e l l i n g 2 2.01 .03 p a r t i c i p a n t s ) , a n d w h e t h e r t h e r e was an i n t e r a c t i o n b e t w e e n t h e two v a r i a b l e s . A n a l y s i s r e v e a l e d a n o n s i g n i f i c a n t t y p e o f d e s i g n m a i n e f f e c t , F ( l , 5 7 ) = . 0 4 , p_<.83, i n d i c a t i n g t h a t t h e m a g n i t u d e o f s t r e s s r e d u c t i o n w i t h i n ( p r e - t o p o s t - ) an e x e r c i s e g r o u p i s e q u a l t o t h e d i f f e r e n c e i n p r e - t o p o s t -c h a n g e b e t w e e n an e x e r c i s e g r o u p a n d a c o n t r o l g r o u p . T h i s f i n d i n g i m p l i e s t h a t i t i s t h e e x e r c i s e p e r s e , a n d n o t j u s t g r o u p • i n v o l v e m e n t w h i c h c a u s e s t h e a n x i e t y r e d u c t i o n . T h e r e was no s i g n i f i c a n t d e s i g n by s t r e s s l e v e l i n t e r a c t i o n , F ( l , 5 7 ) = 2 . 2 5 , p_<.14. T h i s e f f e c t ( i . e . , n o n s i g n i f i c a n t d e s i g n e f f e c t ) h e l d t r u e f o r b o t h s t r e s s e d a n d m i n i m a l l y s t r e s s e d g r o u p s . S t r e s s l e v e l . The d e s i g n b y s t r e s s l e v e l ANOVA i n d i c a t e d a s i g n i f i c a n t s t r e s s l e v e l e f f e c t , F ( l , 57) = 8 . 0 9 , p_<.01. E x a m i n i n g t h e means o f t h e m i n i m a l l y s t r e s s e d g r o u p (M = .44) a n d t h e s t r e s s e d g r o u p (M = . 7 7 ) , i t a p p e a r s t h a t e x e r c i s e h a d more e f f e c t on s t r e s s e d p e o p l e ' s a n x i e t y . A d e s i g n b y s t r e s s l e v e l ANOVA f o r e a c h p s y c h o l o g i c a l m e a s u r e l e v e l ( i . e . , s t a t e a n d t r a i t a n x i e t y ) r e v e a l e d a s i g n i f i c a n t s t r e s s l e v e l e f f e c t f o r s t a t e a n x i e t y , F ( l , 2 5 ) = 4 . 9 2 , p_<.04. I t a p p e a r s t h a t s t r e s s e d p e o p l e r e d u c e d t h e i r s t a t e a n x i e t y more t h a n m i n i m a l l y s t r e s s e d p e o p l e . A n o n s i g n i f i c a n t s t r e s s l e v e l m a i n e f f e c t f o r t r a i t a n x i e t y , F ( l , 2 8 ) = 3 . 4 7 p_<.07, i n d i c a t e s t h a t t h e s t r e s s e d a n d m i n i m i n a l l y s t r e s s e d p e o p l e r e d u c e d t h e i r t r a i t a n x i e t y s i m i l a r l y . H o w e v e r , s h o w i n g t h a t s t a t e a n x i e t y i s s i g n i f i c a n t a t p_<.04 a n d t r a i t a n x i e t y i s n o n s i g n i f i c a n t a t 60 p_<.07, d o e s n o t n e c e s s a r i l y i m p l y t h a t t h e r e i s a d i f f e r e n c e b e t w e e n s t a t e a n d t r a i t a n x i e t y . To t e s t t h i s d i r e c t l y , a s t r e s s l e v e l b y p s y c h o l o g i c a l m e a s u r e ANOVA was c o n d u c t e d . T h e r e was a n o n s i g n i f i c a n t p s y c h o l o g i c a l m e a s u r e m a i n e f f e c t , F ( l , 57) = 3.37, p_<.07 i n d i c a t i n g t h a t t h e r e i s no d i f f e r e n c e b e t w e e n t h e r e d u c t i o n o f s t a t e a n d t r a i t a n x i e t y . T h e r e was a n o n s i g n i f i c a n t p s y c h o l o g i c a l m e a s u r e b y s t r e s s l e v e l i n t e r a c t i o n , F ( l , 5 7 ) = .01, p_<.92. F u r t h e r e x a m i n a t i o n o f s t r e s s l e v e l i n c l u d e d a p r o g r a m l e n g t h b y s t r e s s l e v e l ANOVA t o s e e w h e t h e r p r o g r a m l e n g t h a f f e c t e d t h e amount o f s t r e s s r e d u c t i o n , a n d i f a n y s u c h e f f e c t was r e l a t e d t o i n i t i a l s t r e s s l e v e l . T h e r e were n o n s i g n i f i c a n t p r o g r a m l e n g t h a n d s t r e s s l e v e l m a i n e f f e c t s , F(2,55) = 2.12, p_<.13; F ( l , 55) = 3.76, p_<.06, b u t a s i g n i f i c a n t s t r e s s l e v e l b y p r o g r a m l e n g t h i n t e r a c t i o n , F (2 , 55) = 6.93, p_<.01. I n v e s t i g a t i n g t h e m e a n s , t h e r e i s an i n d i c a t i o n t h a t m i n i m a l l y s t r e s s e d p e o p l e r e d u c e d t h e i r s t r e s s l e v e l s t h e m o s t i n a 6 t o 8-week e x e r c i s e p r o g r a m (M = .65) w h e r e a s s t r e s s e d p e o p l e r e d u c e d t h e i r s t r e s s l e v e l s t h e most i n a 8 t o 12-week (M = .92) e x e r c i s e p r o g r a m ( s e e F i g u r e 1). The p r o g r a m l e n g t h by s t r e s s l e v e l i n t e r a c t i o n was e x a m i n e d more c l o s e l y by b r e a k i n g i t down t o s t a t e a n d t r a i t v a r i a b l e s . To t h i s e n d , ANOVAS were c o n d u c t e d f o r p r o g r a m l e n g t h b y s t r e s s l e v e l s e p a r a t e l y f o r s t a t e a n d t r a i t a n x i e t y . T h e r e were s i g n i f i c a n t s t r e s s l e v e l b y p r o g r a m l e n g t h i n t e r a c t i o n s , F (2 , 23) = 10.33, p_<.01; F(2,26) = 5.37, £ < . 0 1 , Figure 1 6 to 8 8 to 12 12-plus Program Length/Weeks Minimal Stress H — Stressed 62 f o r s t a t e a n d t r a i t a n x i e t y , r e s p e c t i v e l y . The n a t u r e o f t h e i n t e r a c t i o n was q u i t e d i f f e r e n t f o r s t a t e a n d t r a i t a n x i e t y . L o o k i n g a t t h e m e a n s , i t a p p e a r s t h a t m i n i m a l l y s t r e s s e d p e o p l e r e d u c e d t h e i r s t a t e a n x i e t y t h e m o s t i n t h e 8 - t o 1 2 -week e x e r c i s e p r o g r a m (M = .51) a n d t h e l e a s t r e d u c t i o n o f s t a t e a n x i e t y o c c u r r e d i n t h e 6- t o 8 -week (M = .27) a n d 12 p l u s week e x e r c i s e p r o g r a m s (M = . 0 9 ) . H o w e v e r , s t r e s s e d p e o p l e r e d u c e d t h e i r s t a t e a n x i e t y t h e m o s t i n t h e 12 p l u s week e x e r c i s e p r o g r a m (M = 1.2) a n d t h e l e a s t i n t h e 6- t o 8 -week p r o g r a m (M = . 1 3 ) . T h e s e two p r o g r a m c o n d i t i o n s o n l y h a d 2 e f f e c t s i z e s f o r e a c h c o n d i t i o n s o t h a t t h e s e f i n d i n g s a r e n o t r o b u s t ( s e e F i g u r e 2 ) . In e x a m i n i n g t h e means o f t h e s t r e s s l e v e l b y p r o g r a m l e n g t h i n t e r a c t i o n f o r t r a i t a n x i e t y a d i f f e r e n t p a t t e r n o f a n x i e t y r e d u c t i o n was s e e n . M i n i m a l l y s t r e s s e d p e o p l e r e d u c e d t h e i r t r a i t a n x i e t y t h e m o s t i n t h e 6- t o 8 -week p r o g r a m (M = . 7 5 ) , l e v e l i n g o f f a t t h e 8- t o 12 -week a n d 12 p l u s week p r o g r a m s (M = . 2 3 ) . The s t r e s s e d p e o p l e r e d u c e d t h e i r t r a i t a n x i e t y t h e most i n t h e 8 - t o 12 -week p r o g r a m (M = 1 .12) w h i l e t h e l e a s t e f f e c t s o c c u r r e d i n t h e 6 - t o 8 -week (M = .33) a n d 1 2 - p l u s week e x e r c i s e p r o g r a m s (M = .32) ( s e e F i g u r e 3 ) . H o w e v e r , t h e mean o f 1 .12 f o r s t r e s s e d p e o p l e i s i n f l a t e d due t o two v e r y l a r g e e f f e c t s i z e s ( t h e S e t a r o s t u d y u s i n g an a e r o b i c e x e r c i s e a n d c o u n s e l l i n g p r o g r a m ) . When t h e s e e f f e c t s i z e s a r e e x c l u d e d , t h e mean d r o p s t o . 8 6 . The p a t t e r n o f c h a n g e t h e r e f o r e r e m a i n s t h e same b u t l e s s p r o n o u n c e d , Figure 2 State Anxiety 1.4 6 to 8 8 to 12 12-plus Program Length/Weeks - — Minimal Stress —r— Stressed Figure 3 Trait Anxiety 1.2 0.2 -0 1 1 L _ _ 1 6 to 8 8 to 12 12-plus Program Length/Weeks Minimal Stress —r— Stressed 64 i n d i c a t i n g that while the larg e e f f e c t s i z e s c o n t r i b u t e d to the p a t t e r n i n Figure 3, they were not the sol e cause of the p a t t e r n . Study type. A design by study type ANOVA was computed. There was a s i g n i f i c a n t study type main e f f e c t , F(l,57) = 10.65, p<.01, i n d i c a t i n g that unpublished s t u d i e s have l a r g e r e f f e c t s i z e s than published s t u d i e s . There was a n o n s i g n i f i c a n t design by study type i n t e r a c t i o n , F(l,57) = .51, p_<.49. This was an unexpected f i n d i n g , because unpublished s t u d i e s have a r e p u t a t i o n of having n o n s i g n i f i c a n t f i n d i n g s or methodology l i m i t a t i o n s . Consequently f u r t h e r analyses were conducted i n an attempt to dis c o v e r i f t h i s was a spurious f i n d i n g (e.g., perhaps unpublished s t u d i e s used more h i g h l y s t r e s s e d s u b j e c t s ) . A study type by program length, 2 by 3 f a c t o r i a l ANOVA was conducted. There was a s i g n i f i c a n t study type main e f f e c t , F ( l , 55) = 35.73, p_<.01. The means f o r the study type v a r i a b l e showed th a t unpublished s t u d i e s (M = .96) have greater e f f e c t s i z e s than p u b l i s h e d s t u d i e s (M = .34). There was a s i g n i f i c a n t program length by study type i n t e r a c t i o n , F(2,55) = 5.13, p_<.01. Looking at the means, the gre a t e s t e f f e c t s i z e occurred i n the 8 t o 12-week (M = 1.63) unpublished study c o n d i t i o n (see Figure 4). However, these f i n d i n g s do not help to e x p l a i n why unpublished s t u d i e s have l a r g e r e f f e c t s i z e s . A study type by s t r e s s l e v e l , 2 by 2 f a c t o r i a l ANOVA was Figure 4 Figure 5 66 c o m p u t e d . T h e r e was a s i g n i f i c a n t s t u d y t y p e m a i n e f f e c t , F ( l , 57) = 1 4 . 2 3 , p_<.01, a n d a n o n s i g n i f i c a n t s t u d y t y p e by s t r e s s l e v e l i n t e r a c t i o n , F ( l , 5 7 ) = 3 . 1 9 , p_<.08. T h e r e i s h o w e v e r , a s i m i l a r t r e n d b e t w e e n t h e p u b l i s h e d a n d u n p u b l i s h e d s t u d i e s e v e n t h o u g h t h e e f f e c t - s i z e s a r e u s u a l l y b i g g e r i n t h e u n p u b l i s h e d s t u d i e s ( s e e F i g u r e 5 ) . O t h e r V a r i a b l e s A n a l y s i s o f v a r i a n c e r e v e a l e d n o n s i g n i f i c a n t m a i n e f f e c t s f o r f r e q u e n c y o f p r o g r a m , F ( l , 5 9 ) = 1 . 3 7 , p_<.24; d r o p - o u t , F ( 2 , 58) = . 9 7 , p_<.38; a n d t y p e o f l e a d e r s h i p , F ( 2 , 57) = . 0 2 , p_<.98, i n d i c a t i n g t h a t t h e s e v a r i a b l e s d i d n o t i n f l u e n c e t h e s t u d y o u t c o m e s . T y p e . o f e x e r c i s e was a v a r i a b l e o f i n t e r e s t t o t h i s s t u d y as one o f t h e q u e s t i o n s u n d e r i n v e s t i g a t i o n was w h i c h t y p e o f e x e r c i s e was b e s t s u i t e d f o r s t r e s s r e d u c t i o n . H o w e v e r , when a s t r e s s l e v e l b y t y p e o f e x e r c i s e was p e r f o r m e d , t h e ANOVA c o u l d n o t be c o m p u t e d b e c a u s e some c e l l s i z e s were z e r o . A f r e q u e n c y t a b l e was c o n s t r u c t e d t o e s t a b l i s h t h e c e l l s i z e s f o r t h e s t r e s s l e v e l a c r o s s t y p e o f e x e r c i s e . I t was f o u n d t h a t t h e g r e a t e s t c e l l s i z e was a e r o b i c e x e r c i s e w i t h a c o u n t o f 54 o f 61 e f f e c t s i z e s . T h u s i n d i c a t i n g t h a t a e r o b i c e x e r c i s e was t h e most f r e q u e n t l y u s e d e x e r c i s e p r o g r a m i n e x a m i n i n g t h e e f f e c t o f e x e r c i s e on s t r e s s . Due t o i n s u f f i c i e n t d a t a ( i . e . , d i f f e r e n t t y p e s o f e x e r c i s e p r e s c r i b e d f o r s t r e s s r e d u c t i o n ) , t h e q u e s t i o n , w h i c h t y p e o f e x e r c i s e i s b e s t s u i t e d f o r s t r e s s r e d u c t i o n , r e m a i n s u n a n s w e r e d . 68 D i s c u s s i o n The r e s u l t s o f t h i s s t u d y i n d i c a t e t h a t an a e r o b i c e x e r c i s e p r o g r a m d o e s r e d u c e a n x i e t y . The t y p e o f d e s i g n ( w i t h i n g r o u p c h a n g e a n d c o n t r a s t c h a n g e ) h a d a n o n s i g n i f i c a n t m a i n e f f e c t , t h u s i n d i c a t i n g t h a t e x e r c i s e was a f a c t o r i n r e d u c i n g s t r e s s . One e x p l a n a t i o n f o r t h i s f i n d i n g may be t h a t p e o p l e were a b l e t o e f f e c t i v e l y u s e e x e r c i s e a s a c o p i n g s t r a t e g y t o r e d u c e t h e i r e m o t i o n a l r e s p o n s e t o s t r e s s . The q u e s t i o n , i s e x e r c i s e more e f f e c t i v e i n t r e a t i n g p e o p l e who r e p o r t g r e a t e r s t r e s s l e v e l s t h a n p e o p l e w i t h l e s s s t r e s s , was a n s w e r e d i n t h e a f f i r m a t i v e . S t r e s s e d p e o p l e r e d u c e d t h e i r a n x i e t y s i g n i f i c a n t l y more t h a n t h e m i n i m a l l y s t r e s s e d p e o p l e . T h e s e f i n d i n g s a r e s i m i l a r t o L o n g (1984) a n d S t e p t o e e t a l . (1989) who f o u n d t h a t p a r t i c i p a t i o n i n an e x e r c i s e p r o g r a m r e d u c e d a n x i e t y i n s t r e s s e d p e o p l e . T h e r e was a s i g n i f i c a n t s t r e s s l e v e l m a i n e f f e c t f o r s t a t e a n x i e t y (p_<.04) a n d a n o n s i g n i f i c a n t s t r e s s l e v e l m a i n e f f e c t f o r t r a i t a n x i e t y (p_<.07). S t r e s s e d p e o p l e r e d u c e d t h e i r s t a t e a n x i e t y more t h a n m i n i m a l l y s t r e s s e d p e o p l e , w h e r e a s s t r e s s e d a n d m i n i m a l l y s t r e s s e d p e o p l e r e d u c e d t h e i r t r a i t a n x i e t y s i m i l a r l y . H o w e v e r due t o t h e s m a l l d i f f e r e n c e b e t w e e n s t a t e a n d t r a i t a n x i e t y i t i s n o t c l e a r w h e t h e r t h e r e i s a s i g n i f i c a n t d i f f e r e n c e b e t w e e n s t a t e a n d t r a i t a n x i e t y r e d u c t i o n , Two-way ANOVAS o f p s y c h o l o g i c a l m e a s u r e s b y t y p e o f d e s i g n a n d s t r e s s l e v e l r e v e a l e d n o n s i g n i f i c a n t m a i n e f f e c t s . T h i s i n d i c a t e d t h a t t h e r e was no d i f f e r e n c e i n t h e r e d u c t i o n o f s t a t e a n d t r a i t a n x i e t y f o r p e o p l e p a r t i c i p a t i n g i n an a e r o b i c e x e r c i s e p r o g r a m . T h e r e f o r e , t h e a s s u m p t i o n i s t h a t t h e r e i s no s i g n i f i c a n t d i f f e r e n c e b e t w e e n s t a t e a n d t r a i t a n x i e t y . T h i s a s s u m p t i o n f i t s w i t h L a z a r u s a n d F o l k m a n ' s (1984) m o d e l o f s t r e s s b e c a u s e i f s t r e s s / a n x i e t y i s due t o a p e r s o n ' s p e r c e p t i o n o f a s i t u a t i o n , t h e n b o t h a s p e c t s o f a n x i e t y m u s t be a f f e c t e d . A p e r s o n c o u l d p e r c e i v e c e r t a i n s i t u a t i o n s a s s t r e s s f u l o r h a v e a t e n d e n c y t o p e r c e i v e most s i t u a t i o n s a s s t r e s s f u l , e i t h e r way, t h e p e r s o n w i l l be a b l e t o r e a s s e s s how t h e y e v a l u a t e a s i t u a t i o n o n c e t h e y h a v e a n o t h e r m e t h o d o f c o p i n g ( i . e . , e x e r c i s e ) . G i v e n t h a t t h e s t r e s s l e v e l h a s an e f f e c t on t h e r e d u c t i o n o f s t a t e a n x i e t y , one c a n c o n c l u d e t h a t s t r e s s e d p e o p l e ' s p e r c e p t i o n o f a n x i e t y f o r p a r t i c u l a r s t r e s s f u l s i t u a t i o n s i s c o n s i d e r a b l y d e c r e a s e d a f t e r an e x e r c i s e p r o g r a m . H o w e v e r , t h e t e n d e n c y t o p e r c e i v e s i t u a t i o n s a s a n x i e t y p r o v o k i n g i s d e c r e a s e d s i m i l a r l y f o r b o t h t h e s t r e s s e d a n d m i n i m a l l y s t r e s s e d p e o p l e . I t a p p e a r s t h a t b o t h s t a t e a n d t r a i t a n x i e t y must b e m e a s u r e d t o h a v e an a c c u r a t e s e n s e o f p e o p l e ' s s t r e s s r e d u c t i o n . I d e n t i f y i n g t h e s p e c i f i c c o n d i t i o n s t h a t e v o k e s t a t e a n x i e t y i n p e r s o n s who d i f f e r i n t r a i t a n x i e t y b e f o r e an e x e r c i s e p r o g r a m a n d o b s e r v i n g w h e t h e r t h o s e c o n d i t i o n s c o n t i n u e t o e v o k e a n x i e t y a f t e r t h e e x e r c i s e p r o g r a m may be w o r t h y o f f u r t h e r s t u d y . 70 T h e r e was n o t s u f f i c i e n t i n f o r m a t i o n r e g a r d i n g t y p e s o f e x e r c i s e p r o g r a m s t o be a b l e t o d e d u c e t h e most e f f e c t i v e t y p e o f e x e r c i s e f o r s t r e s s r e d u c t i o n . The m a j o r i t y o f e x e r c i s e p r o g r a m s ( i . e . 8 9 % ) u s e d a e r o b i c e x e r c i s e a s an i n t e r v e n t i o n f o r s t r e s s a n d 8% u s e d a c o m b i n a t i o n o f a e r o b i c e x e r c i s e a n d an a l t e r n a t i v e t r e a t m e n t . T h e s e f i n d i n g s c e r t a i n l y s u p p o r t t h e n o t i o n t h a t a e r o b i c e x e r c i s e i s t h e most commonly p r e s c r i b e d e x e r c i s e t r e a t m e n t f o r s t r e s s ( D o r i n s k y , 1 9 8 4 ; T a y l o r e t a l . , 1 9 8 5 ) . I t i s s t i l l u n c l e a r a s t o w h e t h e r a e r o b i c e x e r c i s e i s t h e o n l y f o r m o f e x e r c i s e w h i c h w o u l d e f f e c t i v e l y r e d u c e a n x i e t y . M o s e s e t a l . ( 1 9 8 9 ) a n d S t e p t o e e t a l . ( 1 9 8 9 ) d i s c o v e r e d t h a t m o d e r a t e a e r o b i c e x e r c i s e r e d u c e d a n x i e t y , w h e r e a s i n t e n s e a e r o b i c e x e r c i s e d i d n o t . T h i s r a i s e s t h e q u e s t i o n , what i s t h e most e f f e c t i v e i n t e n s i t y o f e x e r c i s e f o r r e d u c i n g a n x i e t y ? F u t u r e s t u d i e s s h o u l d c o n s i d e r l o o k i n g a t t h e d i f f e r e n t t y p e s o f e x e r c i s e a n d t h e i r i n t e n s i t i e s as p r o s p e c t i v e s t r e s s r e d u c i n g s t r a t e g i e s . .The o n e - w a y ANOVA on p r o g r a m l e n g t h r e v e a l e d a s i g n i f i c a n t p r o g r a m l e n g t h e f f e c t . In e x a m i n i n g t h e means t h e 8- t o 1 2 - w e e k p r o g a m h a d t h e g r e a t e s t e f f e c t s i z e a n d t h e 1 2 p l u s - w e e k p r o g r a m h a d t h e s m a l l e s t e f f e c t s i z e . T h u s t h e l e n g t h o f an e x e r c i s e p r o g r a m i n t e r v e n t i o n f o r s t r e s s m i g h t be a s s i g n i f i c a n t a s any o t h e r t y p e o f p s y c h o l o g i c a l i n t e r v e n t i o n l e n g t h . E x a m i n a t i o n o f p r o g r a m l e n g t h s f o r p s y c h o l o g i c a l i n t e r v e n t i o n s h a s shown t h a t i n i t i a l l y t h e p a r t i c i p a n t s r e c e i v e c o n s i d e r a b l e r e l i e f a n d t h e n i m p r o v e m e n t s i n c r e a s e 71 g r a d u a l l y as the number of sessions grow. P s y c h o l o g i c a l i n t e r v e n t i o n s of b r i e f to intermediate d u r a t i o n have b e t t e r outcomes f o r people who are l e s s d i s t u r b e d ( G a r f i e l d & Bergin, 1986) . The s t r e s s l e v e l by program length ANOVA showed a s i g n i f i c a n t program by s t r e s s l e v e l i n t e r a c t i o n . M i n i m a l l y s t r e s s e d people decreased t h e i r s t r e s s l e v e l the most i n a 6-to 8-week e x e r c i s e program, whereas s t r e s s e d people decreased t h e i r s t r e s s l e v e l the most i n the 8- to 12-week e x e r c i s e program. One p o s s i b l e explanation i s that minimally s t r e s s e d people decreased t h e i r s t r e s s i n the shor t e r time frame as t h e i r s t r e s s was minimal and they q u i c k l y reached a c e i l i n g e f f e c t . However, s t r e s s e d people took longer t o reduce t h e i r s t r e s s l e v e l and then (as seen i n Figure 1) once having reached t h e i r maximum s t r e s s r e d u c t i o n , tapered o f f i n the l e v e l of s t r e s s r e d u c t i o n . One can assume tha t once s t r e s s e d , people would need time not only to l e a r n a d i f f e r e n t coping s t r a t e g y f o r s t r e s s f u l s i t u a t i o n s but a l s o r e q u i r e time to apply the st r a t e g y i n order to decrease the s t r e s s . In order to f u r t h e r examine the s t r e s s r e d u c t i o n p a t t e r n , the s t r e s s l e v e l by program length ANOVA was a l s o computed se p a r a t e l y f o r s t a t e and t r a i t a n x i e t y . Both aspects of anxiet y r e d u c t i o n were a f f e c t e d d i f f e r e n t l y by the program length. The expl a n a t i o n f o r the d i f f e r e n c e i n both aspects of anxiet y r e d u c t i o n i s not c l e a r . The (exercise) program length however, appears to play a part i n the p a t t e r n of s t r e s s 72 r e d u c t i o n . There i s no l i t e r a t u r e t o date c o n c e r n i n g the importance of program l e n g t h i n e f f e c t i n g a change i n p a r t i c i p a n t s ' a n x i e t y measures, however t h e r e i s r e s e a r c h c o n c e r n i n g the program lengths f o r p s y c h o l o g i c a l i n t e r v e n t i o n s f o r s t r e s s ( G a r f i e l d & B e r g i n , 1986) . Researchers have a r b i t r a r i l y d e s i g n a t e d a program l e n g t h to f i t the e x e r c i s e p r e s c r i p t i o n g u i d e l i n e s . I t appears t h a t to e f f e c t i v e l y reduce s t a t e a n x i e t y , a 8- t o 12-week e x e r c i s e program f o r m i n i m a l l y s t r e s s e d people and a 12 p l u s week e x e r c i s e program f o r s t r e s s e d people c o u l d be p r e s c r i b e d . In order t o reduce t r a i t a n x i e t y the p r e s c r i p t i o n would be s l i g h t l y d i f f e r e n t , a 6- to 8-week e x e r c i s e program i s s u i t a b l e f o r m i n i m a l l y s t r e s s e d people and a 8- to 12-week e x e r c i s e program f o r s t r e s s e d i n d i v i d u a l s . While i t i s u n c l e a r as to the reason both aspects of a n x i e t y r e d u c t i o n were a f f e c t e d d i f f e r e n t l y by the program le n g t h , r e s u l t s of follow-up s t u d i e s may shed some l i g h t on the d i f f e r i n g p a t t e r n s of a n x i e t y r e d u c t i o n . The f o l l o w - u p r e s u l t s of Steptoe et a l . (1989) and Long and Haney (1988) r e p o r t e d a c o n t i n u a t i o n of t r a i t a n x i e t y r e d u c t i o n from p r e -t e s t t o 3-month follow-up. These r e s u l t s r e f u t e the decrease i n t r a i t a n x i e t y r e d u c t i o n a f t e r 12-weeks of an e x e r c i s e program. There might be a d i f f e r e n c e i n c o n t i n u i n g an e s t a b l i s h e d program and p a r t i c i p a n t s c o n t i n u i n g e x e r c i s e at t h e i r own convenience i n the follow-up p e r i o d . A p a u c i t y of follow-up data concerning the e f f e c t s of an e x e r c i s e 73 i n t e r v e n t i o n p r o g r a m on a n x i e t y r e d u c t i o n d o e s n o t a l l o w f o r f u r t h e r e x a m i n a t i o n . K a z d i n a n d W i l s o n (1978) s t a t e t h a t " a n i m p o r t a n t , a n d w i d e l y r e c o g n i z e d c r i t e r i o n f o r e v a l u a t i n g t r e a t m e n t i s t h e d u r a b i l i t y o f t h e r a p e u t i c c h a n g e " ( p . 1 2 1 ) . T h i s s t a t e m e n t i s u p h e l d b y t h e r e s u l t s o f L o n g a n d H a n e y (1988) a n d S t e p t o e e t a l . (1989) w h i c h s h o w e d t h e d u r a b i l i t y o f t h e e x e r c i s e i n t e r v e n t i o n . The e x a m i n a t i o n o f t h e s t u d y t y p e v a r i a b l e a l s o o f f e r e d u s e f u l i n f o r m a t i o n . The u n p u b l i s h e d s t u d i e s h a d a g r e a t e r mean e f f e c t s i z e t h a n t h e p u b l i s h e d s t u d i e s . When t h e means o f t h e 2 - l e v e l s i n s t u d y t y p e were e x a m i n e d a c r o s s v a r i a b l e s s u c h a s d e s i g n , p s y c h o l o g i c a l m e a s u r e , s t r e s s l e v e l a n d p r o g r a m l e n g t h , i t was f o u n d t h a t t h e t r e n d f o r b o t h l e v e l s was t h e s a m e . S i n c e t h e p a t t e r n o f a n x i e t y r e d u c t i o n a n d p r o g r a m l e n g t h was s i m i l a r i n b o t h l e v e l s o f s t u d y t y p e , t h e a r g u m e n t b y o t h e r r e s e a r c h e r s t h a t G l a s s e t a l . (1981) s h o u l d n o t i n c l u d e u n p u b l i s h e d s t u d i e s i n a m e t a - a n a l y s i s i s u n f o u n d e d . H o w e v e r , t h e r e i s no a p p a r e n t e x p l a n a t i o n f o r t h e d i f f e r e n c e i n e f f e c t s i z e s f o r t h e p u b l i s h e d a n d u n p u b l i s h e d s t u d i e s . In summary , t h e r e s u l t s d e m o n s t r a t e d t h a t a e r o b i c e x e r c i s e was an e f f e c t i v e s t r e s s r e d u c e r a n d t h a t s t r e s s e d p e o p l e d e c r e a s e d t h e i r a n x i e t y more t h a n m i n i m a l l y s t r e s s e d p e o p l e . T h e a v e r a g e e f f e c t s i z e s f o r s t a t e a n d t r a i t a n x i e t y r e d u c t i o n were s i m i l a r , b u t d i f f e r e d c o n s i d e r a b l y u n d e r d i f f e r e n t c o n d i t i o n s o f s t r e s s l e v e l a n d p r o g r a m l e n g t h . F u t u r e s t u d i e s p r o b a b l y n e e d t o m e a s u r e s t a t e a n d t r a i t a n x i e t y t o g e t h e r when e x a m i n i n g t h e e f f e c t s o f e x e r c i s e on s t r e s s . E x e r c i s e p r o g r a m l e n g t h p r o b a b l y p l a y s a r o l e i n t h e m o s t e f f e c t i v e i n t e r v e n t i o n f o r a n x i e t y r e d u c t i o n i n s t r e s s l e v e l . W h i l e u n p u b l i s h e d s t u d i e s h a d t h e g r e a t e r e f f e c t s i z e , t h e t r e n d s o f c h a n g e were s i m i l a r i n b o t h t h e p u b l i s h e d a n d u n p u b l i s h e d s t u d i e s . T h i s m e t a - a n a l y s i s h a s e l u c i d a t e d i n f o r m a t i o n r e g a r d i n g t h e e f f e c t i v e n e s s o f e x e r c i s e a s a s t r e s s r e d u c e r a n d t h e p o p u l a t i o n f o r w h i c h i t i s most e f f e c t i v e . I t h a s b r o u g h t t o l i g h t i n f o r m a t i o n r e g a r d i n g t h e e f f e c t o f an e x e r c i s e p r o g r a m l e n g t h i n a n x i e t y r e d u c t i o n . W h i l e t h e e x p l a n a t i o n f o r t h e e f f e c t o f an e x e r c i s e p r o g r a m i n a n x i e t y r e d u c t i o n i s u n c l e a r , f u t u r e r e s e a r c h c o u l d p o s s i b l y t a k e p r o g r a m l e n g t h i n t o a c c o u n t when p r e s c r i b i n g an e x e r c i s e i n t e r v e n t i o n f o r s t r e s s . One o f t h e l i m i t a t i o n s o f t h i s s t u d y was t h e u n a v a i l a b i l i t y o f i n f o r m a t i o n f r o m p a r t i c i p a n t s who d r o p p e d . o u t o f t h e s t u d i e s i n c l u d e d i n t h e m e t a - a n a l y s i s . F i n a l l y , t h e i n f o r m a t i o n t h a t w o u l d be u s e f u l t o a d d t o o u r p r e s e n t k n o w l e d g e c o n c e r n i n g t h e e f f e c t s o f e x e r c i s e on s t r e s s s h o u l d be a d d r e s s e d . R e c o m m e n d a t i o n s The m e c h a n i s m s t h a t m e d i a t e t h e b e n e f i c i a l e f f e c t s o f e x e r c i s e on c o g n i t i v e p r o c e s s e s c o u l d b e e x t e n s i v e l y s t u d i e d . L a z a r u s a n d F o l k m a n ' s t h e o r y o f s t r e s s i s an e x c e l l e n t s t e p p i n g s t o n e t o e x p a n d on r e s e a r c h i n t h i s a r e a . T h e i r t h e o r y o f s t r e s s f o c u s e s on t h e p e r s o n ' s p e r c e p t i o n o f what i s s t r e s s f u l a n d t h i s c o n c e p t c o u l d be u s e d t o a s c e r t a i n t h e 75 s t r e s s f u l a n d t h i s c o n c e p t c o u l d be u s e d t o a s c e r t a i n t h e s i t u a t i o n s w h i c h a r e s t r e s s f u l t o t h e p e o p l e p a r t i c i p a t i n g i n a r e s e a r c h s t u d y . T h e r e w o u l d be o p p o r t u n i t y t o e x a m i n e t h e s p e c i f i c s i t u a t i o n s w h i c h a r o u s e s t a t e a n x i e t y w i t h i n p e o p l e o f d i f f e r i n g t r a i t a n x i e t y a n d a l s o t o i d e n t i f y t h e i r c o p i n g s t r a t e g i e s . P e o p l e who a r e f e e l i n g s t r e s s e d c o u l d b e a s k e d t o i d e n t i f y t h e s i t u a t i o n s a t h o m e / w o r k w h i c h a r o u s e t h e i r a n x i e t y a n d t h e n g r o u p s c o u l d b e s u b j e c t e d t o v a r y i n g t y p e s o f e x e r c i s e p r o g r a m s a f t e r w h i c h t h e p a r t i c i p a n t s s t a t e - t r a i t a n x i e t y w o u l d be r e t e s t e d . T h e r e i s a l s o a n e e d t o h a v e more s p e c i f i c i n f o r m a t i o n r e g a r d i n g e x e r c i s e p r o g r a m s i n o r d e r t o p r e s c r i b e t h e most e f f e c t i v e e x e r c i s e i n t e r v e n t i o n f o r a p a r t i c u l a r p o p u l a t i o n . What i s t h e o p t i m a l t y p e , i n t e n s i t y , l e n g t h a n d f r e q u e n c y o f e x e r c i s e r e q u i r e d t o e f f e c t i v e l y r e d u c e s t r e s s ? In o r d e r t o e v a l u a t e t h e l o n g - t e r m e f f e c t s o f e x e r c i s e a s an i n t e r v e n t i o n f o r s t r e s s , s t u d i e s n e e d t o i n c o r p o r a t e f o l l o w - u p p r o c e d u r e s i n t h e r e d e s i g n s . 76 R e f e r e n c e s TAbad ie , B . R. (1987) . The p h y s i o l o g i c a l a n d p s y c h o l o g i c a l e f f e c t s o f an e n d u r a n c e e x e r c i s e p r o g r a m on an o l d e r a d u l t p o p u l a t i o n ( D o c t o r a l d i s s e r t a t i o n , U n i v e r s i t y o f M i s s i p p i , 1987) . D i s s e r t a t i o n / A b s t r a c t s I n t e r n a t i o n a l , 47,(10-A) 3693. A b o o d , D. A . (1984). The e f f e c t s o f a c u t e p h y s i c a l e x e r c i s e on t h e s t a t e a n x i e t y a n d m e n t a l p e r f o r m a n c e o f c o l l e g e women. A m e r i c a n C o r r e c t i v e T h e r a p y J o u r n a l , M a y - J u n e , 69-74. A m e r i c a n P s y c h i a t r i c A s s o c i a t i o n . (1980). D i a g n o s t i c a n d  s t a t i s t i c a l m a n u a l o f m e n t a l d i s o r d e r s (3rd e d . ) . W a s h i n g t o n D C : A u t h o r . t B a h r k e , M. S . , & M o r g a n , W. P . (1978). 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Study Type Dowbig-g i n 1975 s t u d -e n t s min. s t r e s s STAI t r a i t A e r o b i c 6 Unpub F o l k i n s 1976 work men min. s t r e s s MA-AACL A e r o b i c 12 Pub Blumen-t h a l e t a l . 1982 work a d u l t s min. s t r e s s POMS STAI A e r o b i c 10 Pub McGlynn et a l . 1983 s t u d -e n t s min. s t r e s s STAI A e r o b i c 14 Pub Jacobs e t a l . 1983 s t u d -e n t s min. s t r e s s STAI • t r a i t A e r o b i c 8 Unpub Eby 1984 s t u d -e n t s min. s t r e s s STAI t r a i t A e r o b i c 6 Unpub D o r i n s k y 1984 work women s t r e s s POMS A e r o b i c 10 Pub Long 1984 work a d u l t s s t r e s s STAI A e r o b i c 10 Pub B o y l l 1985 s t u d -e n t s min. s t r e s s STAI t r a i t A e r o b i c 6 . Unpub G o l d -water et a l . 1985 s t u d -e n t s min. s t r e s s MAS A e r o b i c 6 Pub S e t a r o 1985 work a d u l t s s t r e s s MMPI t r a i t A e r o b i c Aer & co u n s e l 10 Unpub CO Author Year Sample S t r e s s L e v e l Psych. Measure Exer. Type Wks o f Ex. Study Type Wi l s o n 1985 n u r s e s t r e s s STAI A e r o b i c 16 Unpub Abadie 1986 s e n i o r min. s t r e s s STAI t r a i t A e r o b i c 12 Unpub Hughes et a l . 1986 s t u d -e n t s min. s t r e s s POMS A e r o b i c 12 Unpub J e w e l l 1987 s t u d -e n t s min. s t r e s s POMS STAI t r a i t A e r o b i c 16 Unpub Berger e t a l . 1988 s t u d -e n t s min. s t r e s s POMS A e r o b i c 12 Pub Labbe et a l . 1988 women min. s t r e s s STAI A e r o b i c 6 Pub Long & Haney 1988 work women-s t r e s s STAI t r a i t A e r o b i c 8 Pub Nagy e t a l . 1988 a d u l t s min. s t r e s s POMS A e r o b i c 15 Pub Netz et a l . 1988 work a d u l t s min. s t r e s s STAI t r a i t A e r o b i c 12 Pub Simons & B i r k i m e r 1988 a d u l t s min. s t r e s s POMS A e r o b i c 8 Pub Moses e t a l 1989 work a d u l t s min. s t r e s s POMS A e r o b i c 10 Pub Ste p t o e e t a l 1989 work a d u l t s s t r e s s POMS STAI t r a i t A e r o b i c 10 Pub r-A u t h o r Year Sample S t r e s s L e v e l P s y c h . Measure E x e r . Type Wks of Ex. Study t y p e Topp 1989 s t u d -e n t s s t r e s s Test anx. A e r o b i c 7 Pub. Note. P s y c h . = p s y c h o l o g i c a l ; E x / E x e r . = e x e r c i s e ; min. s t r e s s = m i n i m a l s t r e s s . 

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