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Prevalence of exercise induced arterial hypoxemia in healthy females Richards, Jennifer Clarke 2003

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P R E V A L E N C E OF EXERCISE INDUCED A R T E R I A L H Y P O X E M I A IN H E A L T H Y F E M A L E S by Jennifer Clarke Richards B.H.K, The University of British Columbia, 2001 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS OF M A S T E R OF SCIENCE In F A C U L T Y OF G R A D U A T E STUDIES SCHOOL OF H U M A N KINETICS We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH C O L U M B I A July, 2003 © Jennifer C. Richards . UBC Rare Books and Special Collections - Thesis Authorisation Form Page 1 of 1 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r a n a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e a n d s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d b y t h e h e a d o f my d e p a r t m e n t o r b y h i s o r h e r r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t o f t" \jw^a>-<^ The U n i v e r s i t y o f B r i t i s h C o l u m b i a V a n c o u v e r , C a n a d a http://www.library.ubc.ca/spcoll/thesauth.html 7/14/2003 A B S T R A C T Exercise induced arterial hypoxaemia (EIAH) is reported to occur in ~ 50% of highly trained male aerobic athletes. EIAH can have detrimental effects on athletic performance. Reversal of EIAH has been reported to increase maximal oxygen consumption (V02max) and endurance performance time in some subjects during heavy exercise. The number of investigations involving EIAH and females are small, and the results thus far are controversial. It has been reported that some females experience EIAH at a relatively lower fitness level compared to males, while other studies report that the prevalence in females is no different from that of males. Anatomical differences may predispose females to certain EIAH mechanisms, which may increase the prevalence of EIAH in this population. Expiratory flow limitation has been correlated to EIAH in women and may contribute to inspiratory muscle fatigue. Inspiratory muscle fatigue is reported to occur in males following heavy bouts of exercise, however, the relationship between EIAH and inspiratory muscle fatigue in women, had not been determined. The purpose of this investigation was to determine the prevalence of EIAH in females and observe any relationship between EIAH and inspiratory muscle fatigue. The prevalence of EIAH in women was determined in a large sample of females (n = 52, mean = 26.5 years) (V02inax range: 28.0 - 61.3 ml/kg/min). It was hypothesized that EIAH would occur with a greater prevalence and relatively lower % V02max than previously reported in males. Prior to and following exercise, subjects performed a maximal inspiratory pressure (MIP) maneuver of the mouth, and handgrip strength test. The exercise test consisted of an incremental test (50 watts/2.5 min) to exhaustion (V02max) on an electronically braked cycle ergometer. End tidal CO2 (PETCO2) was recorded at each stage of the test. In this study, the prevalence of EIAH in women was slightly greater than that previously reported for males (67 %, n = 35). Hypoxaemic participants were grouped according to their degree of desaturation: mild EIAH Sa02 = 94-92 % (n = 19), and moderate EIAH SaC^ = 91-87% (n = 16). There was no relationship between EIAH and VC^max. Females with a VChmax within 69 % of their predicted value exhibited EIAH. A significant decline in post-exercise MIP was not observed, indicating that inspiratory muscle fatigue was not present. Amongst desaturators, two different patterns were observed. "Fast" desaturation was defined as a drop of 4% or more from baseline SaC>2 within the first two minutes of exercise. "Slow" desaturation was defined as a decline of 4% or more from baseline SaC>2 following five minutes of exercise. Significant differences were present amongst the fast and slow groups. Fast desaturators had a statistically significant lower SaCh, higher breathing frequency, and higher VE / V C 0 2 following the start of exercise. Both fast and slow groups had a significant correlation between Sa02 and VO2 (l/min)(r = - 0.85, r = - 0.88 respectively) although only the slow desaturators showed a correlation between SaC>2 and VE (r = - 0.98). The results of the investigation indicate that EIAH occurs with a slightly greater prevalence in females, than that reported in males, and is not related to VC^max or inspiratory muscle fatigue. In addition, two different patterns of desaturation were observed amongst participants, indicating that fast and slow desaturators may be experiencing EIAH due to different mechanisms. T A B L E OF C O N T E N T S Abstract i i List of Tables v List of Figures vii Dedication viii Introduction 1 Methods 5 Results 11 Discussion 14 References 46 Appendix A Review of Literature 37 Appendix B Group Data 56 Appendix C Individual Raw Data 82 Appendix D Participant Menstrual History 92 Questionnaire and V02max Prediction Equation iv LIST OF T A B L E S Table 1. Subject physical characteristics and 22 resting pulmonary function Table 2. Physical characteristics of non-, mild-, 23 and moderate- E IAH Table 3. Non, mild, and moderate groups physiological measures 24 Table 4. Fast and slow desaturators descriptive statistics 25 Table 5. Mean SaC>2 values (±SD) throughout exercise for non-, 25 mild, and moderate EIAH groups Table 6. Summary of EIAH studies with female participants 44 Table 7. Repeated measures A N O V A non-, mild, and moderate EIAH groups throughout exercise 7-a P E T C 0 2 (mmHg) 56 7-b Ve (1/min) 57 7-cV0 2 '(1/min) 58 7-d V e / V 0 2 (1/min) 59 7-e Ve/VCC-2 60 Table 8. Pearson product moment correlations of physiological measures... 61 throughout exercise for all subjects Table 9. Pearson product moment correlations of physiological 62 variable measured throughout exercise of non-, mild, and moderate EIAH groups Table 10. Repeated measures A N O V A for fast and slow desaturating groups throughout exercise 10-a Ve (1/min) 63 10-b Tidal volume (Vt) ...64 10-c Breathing frequency (Fb) 65 10-d % S a 0 2 66 10-e V 0 2 (1/min) 67 10-f V 0 2 (ml/kg/min) 68 10-g PETC0 2 (mmHg) 69 lO-hVe/VC-2 (1/min) .' .70 10-i Ve/VCC-2 (1/min) 71 Table 11. A N O V A of significantly different variables between fast and slow desaturators, to determine where differences occurred over time 11-a V0 2 ( l /min) 72 11-b V 0 2 (ml/kg/min) 73 11-c % S a 0 2 , 74 11-d Breathing frequency 75 l l - e V e / V C 0 2 76 Table 12. Pearson product moment correlation of physiological 77 variables measured throughout exercise within fast and slow desaturators Table 13. Repeatability measures, Pearson product moment correlation 78 and Bland-Altman test to compare repeated bouts of maximal exercise and % SaQ 2 response . Table 14. One sample t-test of pre and post exercise mean handgrip 79 values for all subjects Table 15. Pre- and post-exercise MLP and handgrip mean values 80 for all subjects Table 16. Hyperoxic Sa0 2 values across time. Repeated measures 81 A N O V A and independent samples t-test. LIST OF FIGURES Figure 1. % Sa02 values for non, mild, and moderate EIAH .27 groups throughout exercise Figure 2. % Sa02 values of fast and slow desaturating groups 28 throughout exercise Figure 3. Ve throughout exercise for fast and slow 29 desaturating groups Figure 4. Breathing frequency of fast and slow desaturating :30 groups throughout exercise FigureS. Tidal volume of fast and slow desaturating groups 31 throughout exercise Figure 6. VE / VC0 2 of fast and slow desaturators 32 throughout exercise Figure 7. VE / V o 2 of fast and slow desaturating 33 groups throughout exercise Figure 8. PETCO2 of fast and slow desaturating 34 groups throughout exercise Figure 9. % Sa02 response to hyperoxic gas during exercise 35 Figure 10. % Sa02 response to hyperoxia and 36 norrnoxia during exercise D E D I C A T I O N To all of my family, thank-you for your relentless support and encouragement I N T R O D U C T I O N In healthy individuals, dynamic exercise increases the demand for oxygen (O2) and the production of carbon dioxide (CO2) from the working muscles. Three major physiological processes occur in order to meet the demands of exercise: 1) increased alveolar ventilation (V A ) , 2) increased cardiac output (Q), and 3) redistribution of Q to enhance perfusion of exercising muscles (Hlastala & Berger, 1996). The pulmonary system is generally able to meet the demands of the working muscles during dynamic exercise by maintaining the partial pressure of arterial oxygen (PaC>2), arterial oxyhaemoglobin saturation (Sa02), and the partial pressure of arterial carbon dioxide (PaC02) within a narrow range. However, decreases in Pa02 and Sa02 during heavy and sub-maximal exercise in male endurance athletes have been reported (Asmussen & Nielsen, 1960; Rowell et al, 1964; Dempsey et al, 1984; Powers et al, 1988; Rice et al, 1999). The decline in Sa02 during exercise has been termed exercise induced arterial hypoxaemia (EIAH) (Dempsey et al, 1984). At least a 3% decrease in Sa02 from a baseline of -98 % is defined as EIAH (Dempsey & Wagner, 1999). Arterial O2 content (Ca02) is directly related to haemoglobin concentration and Sa02 (Levitsky, 1999). Therefore as Pa0 2 and Sa02 decline, so does C a 0 2 and thus the rate of oxygen consumption (VO2). A decrease in Sa02 and the subsequent drop in Ca02 can have a deleterious effect on athletic performance. In males, there is a significant linear correlation between exposure to acute hypoxia (FIO2 = 14 % ) and decrease in V02inax (r = 0.94) (Lawler et al, 1988)! In addition, Koskolou and McKenzie (1994) examined the effects of mild (FIO2 = 18 %) and moderate (FI02= 16 %) induced hypoxaemia on a 5 minute cycle performance on seven highly trained male cyclists, who did not develop EIAH. Pulse oximetry readings associated with the mild and moderate hypoxaemia were 90 % Sa02 and 87 % Sa02 respectively. There was an inverse relationship between % Sa02 and 1 work output (Koskolou & McKenzie, 1994). It has also been reported that for every 1% reduction in SaC*2 (more than 3% from baseline), there is a 2% reduction in VC^max in women (Harms et al, 2000). EIAH has been examined using primarily male subjects, where it is estimated to occur in approximately 50% of elite male endurance athletes (Powers et al, 1988). The mechanisms for E I A H have been investigated and remain controversial (Dempsey & Wagner, 1999). Potential mechanisms include: veno-arterial shunt (Dempsey et al, 1984), ventilation-perfusion inequality (V A /Qc) (Hammond et al, 1986; Hopkins et al, 1994), diffusion limitation (St Croix et al, 1998; Edwards et al, 2000), and relative alveolar hypoventilation (Hopkins & McKenzie, 1989; Durand et al, 2000). Recent work has demonstrated that respiratory muscle fatigue has a negative effect on aerobic exercise capacity (Johnson et al, 1993; Babcock et al, 1995a; Dempsey et al, 1996; Johnson et al, 1996; Babcock, 2002). It is possible that fatigue of the respiratory muscles may occur during heavy exercise whereby the inspiratory muscles are unable to generate the force required to maintain an appropriate V A (Johnson et al, 1996). If V A fails to adequately increase, then it is possible that Pa02 would decrease and PaC02 levels would increase. Indirect evidence to support this hypothesis is seen where an inadequate alveolar ventilatory response during heavy exercise occurs in subjects who exhibit EIAH (Dempsey et al, 1984). Dempsey et al. (1984) demonstratred that when male subjects with EIAH were exposed to further hypoxia and hyperoxia during heavy exercise, there was little effect on minute ventilation suggesting that the subjects were unable to increase their ventilation when given a hypoxic stimulus. However, the resting ventilatory response to hypoxia and hypercapnia in athletes with EIAH is controversial (Hopkins & McKenzie, 1989; Harms & Stager, 1995). Few EIAH investigations have used females as participants and the true prevalence in women remains controversial. Hopkins et al. (2000) state that the prevalence of EIAH in females is no different from males (approximately 50%). In this 2 study, 17 females who possessed a VC^max ranging between 42-61 ml/kg/min were tested using both an incremental exercise test on a treadmill and cycle ergometer. Of these 17 subjects, four (24%) developed EIAH (mean Pa02 = 92 mmHg) and the hypoxaemic women in this investigation had a V02max that was > 180% of predicted. Alternately, Harms et al. (1998) examined 29 female subjects with a similar V02max range (35-70 ml/kg/min) and found that 22 subjects (76 %) developed EIAH (Pa0 2 = 68-91 mmHg, Sa02 = 87-94%) during an incremental treadmill test to exhaustion. Some of the subjects who developed EIAH possessed a V02max that was only within 15% of their predicted value, a phenomenon that does not occur in men (Powers et al 1988), and is in disagreement with Hopkins et al. (2000). E I A H typically occurs in males who have a V02max that is 150% greater than their predicted value (Dempsey et al, 1984; Powers et al, 1988). In addition, Wetter et al. (2000) tested 17 females with a V0 2max range of 44-56 ml/kg/min and found that eight (47%) subjects became hypoxemic (Pa02 = 80-86mmHg, Sa02 = 92-95%). Therefore, the currently reported prevalence of EIAH in females ranges from 24% to 76% (Harms et al', 1998; Hopkins et al 2000; Wetter et al, 2000). Possible reasons why the incidence of EIAH would be different between men and women include differences in resting lung volumes and airway diameter. Females compared to males of the same age, height, and mass have a smaller lung diffusion surface, smaller lung size, and smaller airways (Thurlbeck, 1982). Narrower airways possessed by females can create expiratory flow resistance during heavy exercise, leading to a flow limitation. Following the development of expiratory flow limitation, there is an increase in the work of breathing (i.e. relative lung hyperinflation and disruption of the length-tension relationship of diaphragm) required of the inspiratory muscles, which may lead to their fatigue (McClaran et al, 1998). Most recently it has been shown that in a small group of healthy women (n = 8, V02inax range 42-52 ml/kg/min) there is a significant positive correlation between the degree of expiratory flow limitation and 3 EIAH (r = 0.71) (Walls et al, 2002). However, the relationship between EIAH and inspiratory muscle fatigue has not been, explored in men or women. Hypothesis The prevalence of EIAH in females is unclear. There is evidence to suggest that females develop EIAH at a relatively lower percent of predicted VC^max as compared to men (Harms et al, 1998). This may be attributed to their inherent physiological and anatomical differences (Thurlbeck, 1982). Therefore, the primary objective of this investigation was to determine the prevalence of EIAH in a large female population who posses a wide range of VChmax values. The secondary objective was to determine i f respiratory muscle fatigue was correlated to the degree of EIAH. It was hypothesized that 1) EIAH would occur with a greater prevalence and at relatively lower predicted VChmax than that previously reported in males; and 2) the degree of respiratory muscle fatigue following maximal exercise would be positively correlated to the degree of EIAH. 4 M E T H O D S Participants This investigation received approval from the clinical ethics board of the University of British Columbia. A l l testing occurred at the University of British Columbia within the Health and Integrative Physiology Laboratory in accordance with the Declaration of Helsinki. Fifty-four female participants of varying fitness levels between the ages 18-42 years volunteered for the study and provided written informed consent. Two subjects were later excluded, resulting in a total of 52 female participants. Subjects were recruited from the University campus and local athletic organizations. A l l females were non-asthmatic, non-smokers and had no history or present condition of heart or lung disease. Participants were tested during the early follicular phase of their menstrual cycle, when progesterone levels are reported to be lowest (day 3-8 after the start of menses)(Lebrun et al, 1995). Cycle phase was determined by self-reported menstrual history (Appendix D), and all subjects were required to have had a regular menstrual cycle for at least the past six months. Increased levels of progesterone, associated with the luteal phase of the menstrual cycle, are a known ventilatory stimulus during rest. General Procedures Participants reported to the lab 4 hours post-meal consumption and without caffeine in the past 24 hours. Subjects completed consent forms and physical activity and menstrual history questionnaires followed by spirometry and resting metabolic measures. A cycle test to exhaustion was conducted in addition to pre- and post- measures of respiratory muscle strength and handgrip strength. 5 Spirometry Particpants performed general spirometry measures in accordance with the American Thoracic Society standards (ATS, 1995) (forced vital capacity (FVC), forced expiratory volume in lsec (FEVj.o), forced expiratory flow rate (FEF25-75%) and 12 second maximal voluntary ventilation (MVV)) (Spirolab II, Medical International Research, Vancouver, B.C.). Participants with an F E V i / F V C < 80% were excluded from the investigation. The best of three trials was used to determine the maximum value and individual % of predicted was calculated according to the European Respiratory Society prediction formula (ERS, 1993). Resting Data Resting values (5-10 min) for heart rate (HR) (Polar S410, Finland) and oxyhaemoglobin saturation (Sa02) were measured. Breathing frequency (F b), tidal volume (V t), minute ventilation (VE), O2 consumption (VO2), inspiratory duty cycle (time inspired / time total), were measured with a commercial metabolic cart (Physiodyne, N Y , USA). The pneumotach and gas analyzers were calibrated according to the manufacturer's specifications, using a 3 litre syringe and known gas concentrations. The partial pressure of end tidal CO2 (PETCO2) was recorded by a CO2 analyzer (AEI Applied Electrochemistry, CD-3A, Pittsburgh, Pennsylvania) connected to an A-D board (National Instruments, B N C 2110, Austin, Texas) and output was analyzed by Labview software (National Instruments, Austin, Texas) prior to measuring inspiratory muscle strength. Predicted V02max was determined using a regression equation that incorporated gender, perceived functional ability, physical activity rating, and body mass index (George et al, 1997). 6 Measure of Inspiratory Muscle Strength Maximal inspiratory pressure (MIP) was measured at the mouth, representing the amount of force generated from the inspiratory muscles. During MIP trials, subjects wore a nose clip and breathed normally through a 3-way valve (Hans Rudolph, 2100 series, Kansas City, Missouri) and passively exhaled to functional residual capacity (FRC). Following exhalation, the valve was closed and the subject inhaled maximally, drawing small amounts of air in through a pinhole in the valve, which prevented closure of the glottis. Pressure was measured in volts at the mouth with a differential pressure transducer (Vacuumed model 4510, Ventura, California) and converted to cmH 2 0 (Labview Software, National Instruments Hardware, Austin, Texas). The pressure transducer was calibrated using a sphygmometer. The amount of force generated with each MIP maneuver was graphed (-cmRiO) and the peak was averaged over a period of one second. A l l subjects were given a demonstration and unlimited time to practice the MLP manoeuvre prior to recording each trial. At least 5 trials were conducted until three measures within 5% were attained. The two highest values, of the three, were averaged and used as the MIP value (O'Kroy et al, 1992). Hand Grip Measure Due to the dependency Of MIP measures on an individual's volitional effort, it was important to be able to determine whether a reduction in MIP following exercise was not due to decline in subject motivation (Fuller et al, 1996). Handgrip strength, of the dominant hand, was measured pre and post exercise to determine changes in motivation to perform a maximal effort. Handgrip was measured five times, with a minute rest between trials. The maximal value was determined to be an average of the two highest values within 5% of each other. It was assumed that the forearm muscles would not be fatigued following maximal cycle exercise. 7 Exercise Test Upon completion of spirometry, handgrip and MIP measurements, subjects were instrumented with a pulse oximeter at the ear (Datex-Ohmeda 3800, Colorado, USA) and finger (Criticare systems Inc. 504, Milwaukee, Wisconsin). A vasodilator was applied to the ear prior to instrumenting the participants with the pulse oximeter. If the ear oximeter had a poor signal resulting from either small earlobes or earring holes, the finger oximeter was used to determine saturation throughout the test. Subjects wore a nose clip and breathed through a mouthpiece connected to a non-rebreathing valve (Hans-Rudolph, 2700 series, Kansas City, Missouri). VC^max was determined on an electronically braked cycle ergometer (Excaliber, Quinton Instruments, Gronigen, Netherlands). After a five minute warm-up at 50 watts, the subjects rode a progressive exercise test that increased 50 watts every two and a half minutes until they were unable to continue. During the last 30 seconds of each step, PETCO2 was recorded and averaged. During each minute of the test, heart rate, ear and finger Sa02 were recorded. A l l subjects cycled until volitional exhaustion, and V02max was determined to have been achieved when maximal heart rate was attained (220-age), VO2 plateau, and RER > 1.10. Upon attainment of V02max, subjects immediately began a five minute cool down. The first MIP was recorded five minutes post exercise; followed by an additional MIP every minute up to 10 minutes post exercise. Hand grip strength was recorded between MIP trials. Following the maximal cycle test and post exercise measures, 45 subjects performed an additional maximal cycle test to exhaustion. A minimum of 15 minutes post initial exercise test, subjects were given 5 minutes to warm up at 50 watts, thereafter, the resistance increased 25 watts per minute. This second maximal cycle test was performed to ensure that a maximal VO2 value was attained. 8 Effects of Hyperoxia Eight subjects who exhibited EIAH returned to the lab during the early follicular phase of their menstrual cycle, at least 1 month later (range: 1-4 months). Throughout the hyperoxic exercise test, instrumentation was the same as the initial graded exercise test. A l l subjects were given five minutes to warm-up at 50 watts, thereafter the resistance was manually increased until 80-85% of peak power was attained. SaC>2 was recorded every minute and once the subjects desaturated to similar levels of their first test, 26% 0 2 was administered. This FIO2 was chosen to produce a physiological range of blood gas values. In addition, 26% O2 has been shown to maintain % Sa02 in females during heavy exercise (Harms et al, 2000). The hyperoxic gas was channelled into an airtight container containing 3-4 litres of warm water. The tubing carrying the hyperoxic gas was inserted into the water, at the base of the container, and gas was collected from a separate piece of tubing placed above the water. The warmed and humidified gas was transferred into an airtight reservoir bag. Large bore tubing was attached from the reservoir bag to the mouthpiece, whereby the gas was delivered to the subjects. Reproducibility of EIAH The incremental VChmax test was repeated on 4 subjects during day 3-8 of their menstrual cycle at a later date (1-5 months). Statistical and Data Analyses Following completion of all tests, participants who exhibited E I A H were classified according to their SaC>2 response to exercise (i.e. non-, mild, moderate, severe). For all statistical analyses, significance was set at p < 0.05. Groups were compared using A N O V A . Pearson product moment correlations were utilized to determine linear relationships between: %Sa02 change and decline in post-exercise MIP, V02max and decline in Sa02, and P E T C O 2 and decline in Sa02. The patterns of desaturation were 9 examined among the subjects who exhibited EIAH,. Subjects were grouped according to when they began to exhibit EIAH, either at the initial onset of exercise, or in the later phases of the test. These groups are described as "fast" and "slow" desaturators and are defined as exhibiting E I A H within the first 2 minutes of exercise (fast), or following a minimum of 5 minutes of exercise (slow). Repeated measures A N O V A was used to determine if significant differences existed between fast and slow desaturators throughout the exercise test. A l l data are presented as means ± standard deviations. 10 RESULTS Subject characteristics and pulmonary function Fifty-four female subjects volunteered for the study. Two subjects were excluded due to an FEVj /FVC <80 %. A l l data are reported as n = 52 (V0 2 max range: 28.07 -61.37 ml/kg/min). Subject physical characteristics, spirometry data, and resting PETCO2 values are shown in Table 1. Table 2 compares subject physical characteristics and resting pulmonary function between non-, mild, and moderate EIAH groups. There were no significant differences between groups for age, height, weight, or pulmonary function. Table 3 compares physiological parameters obtained before, during, and following the cycle test in the three EIAH groups. Exercise Data Desaturation has been defined as a drop of 3 % or more from baseline arterial S a 0 2 levels (Dempsey et al, 1984) however, in the present study a drop of 4 % or more was defined as EIAH. Pulse oximetry readings can underestimate % SaC"2 by ~ 1% when compared to arterial blood measures (unpublished data)(Edwards et al, 2000). Of the 52 women studied, 35 desaturated (67 %) and 17 did not (33 %). Of the 35 women who desaturated, 19 women mildly desaturated (94-92 % Sa02) and 16 women moderately desaturated (91-87 % S a 0 2 ) (Figure 1). Non-, mild and moderate EIAH groups' physiological measures were compared and there was a significant difference between groups in % Sa02 (p < .05). Across time there were no significant differences between groups for any measured variable except % S a 0 2 ( T a b l e 3 ) . 11 Patterns of Desaturation Patterns of desaturation were investigated by dividing the EIAH subjects into either fast or slow desaturating groups. Slow desaturation was defined as a drop of 4 % or more from baseline following a minimum of 5 minutes of exercise (150 watts) (Figure 2). Fast desaturation was defined as a drop of 4 % or more within the first 2 minutes of exercise (50 watts) (Figure 2). Table 4 provides descriptive statistics of the fast and slow desaturating groups. There were significant differences (p < 0.05) between fast and slow groups for the following variables: breathing frequency (fb), VO2 (1/min), VE / VC0 2 and SaO-2 (Table 9)(Figure 2-6). In addition, during exercise, fast and slow desaturators both showed a correlation (p < .01) between Sa0 2 and V 0 2 (1 / min) (r = - 0.85) (r == - 0.86). However, only the slow desaturating group possessed a significant correlation between V E and Sa0 2 (r = -0.98) (Table 11). MIP manoeuvre The mean coefficient of variation of individual pre exercise MIP measures was 2.1 ± 3.0 % and 1.5 ± 8.4 % for post exercise MIP. Variation between subjects for % change in post exercise MIP was high (range: - 39% to +28%). There were no significant differences between groups and decline in MIP (Table 3). Handgrip measure There were no significant differences between pre- and post- exercise handgrip measures amongst any subjects (Table 13). 12 Hyperoxic results Figure 9 depicts mean (n = 8) % SaC^ values from rest to end exercise during the hyperoxic test. A l l subjects returned to baseline % SaO-2 values. Reproducibility of EIAH Four subjects returned to the lab on a separate day from the initial maximal exercise test. During the second VC^max test, % Sa02 was recorded and compared to the results of the initial test. It was determined that there was no significant difference for % Sa02 between the first and second exercise test (Table 12). Pearson product moment correlation (r =0.81) was used in addition to a Bland-Altman test to measure repeatability (Bland & Altman, 1986). The Bland-Altman test is generally used to compare two different measures. However, in the present study it was modified to measure the repeatability of EIAH. Second VChmax Test Upon completion of the initial VC^max test, 45 subjects performed an additional cycle test to exhaustion to ensure a maximal VO2 value was attained. Although the two tests were not statistically different, the first VC^max test was, on average, 6.4 % higher than the second. 13 D I S C U S S I O N The main findings of this investigation were that EIAH occurred at a slightly higher prevalence and at relatively lower fitness levels in females compared to that reported for males. The degree of E IAH experienced was not related to a decline in post-exercise MIP or aerobic capacity. Amongst the women who desaturated, two distinct patterns were observed; some women began to exhibit EIAH at sub maximal levels (fast) while others tended to desaturate near the end of exercise (slow). Prevalence of EIAH The prevalence of EIAH in women in this study was 67 %. Of the 35 women who desaturated, 19 (36 %) were grouped as exhibiting mild EIAH (92 - 94 % Sa02) and 16 (31 %) were grouped as exhibiting moderate EIAH (87 -91 % SaOa). Except for % Sa02, there were no significant differences between groups amongst any of the measured physiological variables (Table 5). The prevalence of EIAH in males has been well documented (Rowell et al, 1964; Dempsey et al, 1984; Powers et al, 1988), however few studies have examined EIAH in women and most have used relatively small sample sizes (Harms et al, 1998; Hopkins et al, 2000; Wetter et al, 2000; Walls et al, 2002). While it is generally accepted that approximately 50% of highly trained men will exhibit EIAH, the present study suggests that EIAH occurs in a greater number of women and at a relatively lower fitness level. The present study is in agreement with the work of Harms et al. (1998) who found that 76% of their female participants experienced EIAH. Typically, males who experience EIAH have a V02max that is > 150 % of their predicted value (Rowell et al, 1964; Dempsey et al, 1984; Johnson et al, 1992). In addition, Hopkins et al. (2000) found that EIAH was only present in women who had a V02inax that was >180 % of their predicted, while other studies in women have not found such a relationship (Harms et al, 1998; Walls et al, 2002). In the present 14 investigation, there was no relationship between EIAH and aerobic capacity. Moderate EIAH was observed in women who had a VC^max that was only 69 % of their predicted value (~ 35 ml/kg/min). Other studies have supported the notion that women exhibit EIAH at relatively lower fitness levels compared to males. Harms et al. (1998) reported that half of their female subjects with significant EIAH had a V02max within 15% of predicted normal values (n = 29). Prior to the current study, the largest female EIAH population to be examined was 29, which may explain previous conflicting reports. Inspiratory Muscle Fatigue An explanation as to why women experience EIAH at lower fitness levels and with a greater prevalence is unclear. It is reported that EIAH may be linked to a mechanical constraint that is more common in females due to their inherent anatomical differences (Thurlbeck, 1982; McClaran et al, 1998). Narrower airways and smaller lung volumes possessed by women can contribute to expiratory flow limitation during exercise, resulting in relative alveolar hypoventilation and/or increased work of breathing (McClaran et al, 1998). The result of both alveolar hypoventilation and respiratory muscle fatigue is presumably the inability to adequately ventilate, conceivably leading to EIAH. Although expiratory flow limitation was not directly measured, it has been significantly correlated to EIAH in women (McClaran et al, 1998; Walls et al, 2002). It was hypothesized that women would be more susceptible to expiratory flow limitation during exercise, which could contribute to inspiratory muscle fatigue and subsequent EIAH. Inspiratory muscle fatigue, as measured by a maximal inspiratory pressure maneuver (MIP) is known to occur in males following heavy exercise bouts such as marathon running, a cycle ergometer test, and an endurance triathlon, (Loke et al, 1982; Coast et al, 1990; Hi l l , 1991). However, in the present study, no significant decline in post exercise MIP was observed. In addition, other methods of detecting diaphragm 15 fatigue, such as bilateral phrenic nerve stimulation, have also reported a decline in post exercise diaphragmatic pressure following heavy exercise in males (Babcock et al., 2002). Although a significant finding was not present, there was a wide range of observed post-exercise changes in MIP. The range of percent change amongst all subjects from pre- to post-exercise MIP was a decline of 39 % to an increase of 28 % (cmE^O). Although other studies have documented the presence of diaphragm fatigue following exercise in males, the current study did not detect the presence of inspiratory muscle fatigue in females, possibly due to the large variability observed. Patterns of desaturation Subjects who desaturated were grouped according to their pattern of desaturation (fast or slow). Seven subjects desaturated within the first two minutes of exercise at a work output of less than 40 % of V02max (Table 4, Figure 2). In comparison to other studies with women, Walls et al. (2002) reported that some of their subjects began to desaturate at sub-maximal levels and Harms et al. (1998) also found that 11 of their 15 hypoxemic female subjects desaturated at mild to moderate levels of exercise. In addition, desaturation has been reported to occur during sub maximal cycle exercise in males (Rice et al., 1999). It is likely that different patterns of desaturation represent different mechanisms. A comparison between the fast and slow EIAH groups showed significant differences among SaC^, VO2 (1/min), Fb, and VE / V C 0 2 as well as an interaction effect between groups with VE and Vt (Figures 2 and 6, Table 9). During exercise, fast desaturators had a smaller Vt and a significantly greater Fb (Figures 4.and 5). In addition, fast desaturators had a greater VE until the end of exercise whereupon the slow group surpassed the VE levels of the fast group. Fast desaturators also showed a significantly higher VE / V C 0 2 and lower % SaO-2 throughout exercise (Table 9). Slow desaturators had 16 a % Sa02 that was significantly correlated to their VE, whereas the fast group did not exhibit a significant correlation (Table 11). These observations suggest that differences in patterns of desaturation may be due to ventilation differences. Only a few studies have attempted to examine the mechanisms involved with the occurrence of EIAH at sub-maximal exercise. Aguilaniu et al. (2002) examined the sub-maximal gas exchange disturbance in 14 men by comparing them to 14 matched controls. There were no significant ventilatory differences between groups at sub-maximal exercise. However, at maximal exercise early desaturators exhibited a lesser degree of hyperventilation shown by an increased PaC02. The authors speculate that early desaturation might be attributed to a ventilation-perfusion mismatch. In addition, Rice et al. (1999) observed EIAH at 40 % peak oxygen uptake (150 watts) in 15 competitive male cyclists. PaC02 did not decrease until exercise intensity increased beyond 275 watts, which can be indicative of little or no alveolar hyperventilation. The authors attributed the early onset of E IAH to an inadequate hyperventilation following the first exercise intensity. Although results in males may attribute early onset of EIAH to a lack of compensatory hyperventilation, it is difficult to directly compare these results to women due to little research involving female subjects. In addition, gender differences in breathing patterns during exercise may exist (Kilbride et al, 2003). A comparison of males (n = 14) and females (n = 10) of average fitness revealed that females increased their VE by increasing Fb to a significantly greater degree than males, whereas males utilized Vt increases to attain greater VE levels (Kilbride et al, 2003). In addition, throughout exercise, women had significantly lower PETCO2 levels and greater dead space-tidal volume ratios, indicating that males adopted a more efficient breathing pattern throughout exercise, as the increased volume per breath decreased the impact of anatomical dead space on alveolar ventilation (Kilbride et al, 2003). In the present study PETCO2 values were not statistically significantly different however, PETCO2 17 values appeared to be lower amongst fast desaturators. Although dead space ventilation was not directly measured, lower PETCO2 values coupled with a higher breathing frequency may indicate a greater degree of dead space ventilation. The results of the present investigation suggest that different patterns of desaturation exist in women, which may be attributed to different mechanisms. Fast desaturators had a significant higher breathing frequency and higher VE / V c o 2 ratio which, when accompanied with smaller tidal volumes and lower PETCO2 values, may represent a greater degree of dead space ventilation and a smaller degree of effective alveolar ventilation. If V A fails to adequately increase, then it is possible that Pa02 would decrease and PaCC*2 levels would increase. A decline in PaC>2 can result in a subsequent decline in arterial O2 content and % SaO-2. As exercise time increases and the degree of EIAH worsens, other mechanisms may become involved. McClaran et al. (1998) determined that expiratory flow limitation was present in 12 of 14 highly trained women (VC^max > 57 ml/kg/min) during heavy and maximal treadmill running . In addition, diffusion limitation may play a role in EIAH development at near maximal levels (Warren et al, 1991; Hopkins et al, 1994; Wetter et al, 2001). Possible Study Limitations Arterial blood was not sampled in this study. Pulse oximetry readings do not account for pH and temperature changes in Sa02 values. In order to show that the decline in SaC"2 was not exclusively due pH decreases or temperature increases, hyperoxic tests were conducted on 8 subjects. A l l subjects % Sa02 returned to their resting baseline value. This demonstrates that the desaturation observed was reversible by inhalation of hyperoxic gas and therefore not exclusively due to pH or temperature changes. A l l testing occurred during the early follicular phase (day 3-8) of the menstrual cycle, when progesterone is reported to be at its lowest (Lebrun, 1993). Progesterone is a ventilatory stimulant and is associated with increased hypoxic and hypercapnic 18 respiratory drives as well as VE (England et al, 1976; Lebrun et al, 1995). In addition, increased inspiratory muscle endurance (time to task failure) is reported to be greater with increased progesterone levels however, there are no respiratory muscle strength (MIP) differences across the menstrual cycle (Chen & Tang, 1989). Plasma progesterone was not measured and menstrual cycle phase was determined by self-reported menstrual history. A l l subjects reported to have had a regular menstrual cycle for the past six months or greater. Ovulatory evidence was obtained by a menstrual history questionnaire that determined the existence of symptoms associated with ovulation (Lebrun et al, 1995). In addition, the prevalence of EIAH in any males was not determined. Numerous reports confirm the reported prevalence in highly trained males to be ~ 50% (Dempsey et al, 1984; Powers et al, 1988). Due to the present information available on males and EIAH, the present investigation chose to focus solely on female participants and compare the present results to previously published reports on males. Future Directions Little research has been done concerning women and EIAH, however it appears that there is a slightly greater prevalence of EIAH in females and it does not appear to be related to V0 2 max. Amongst both men and women, EIAH has been observed at sub maximal levels of exercise. Future research should aim to determine why females are more prone to EIAH at relatively lower fitness levels and i f sub maximal EIAH in males and females can be attributed to the same mechanisms. A greater prevalence of EIAH at a relatively lower V02max in females could be due to anatomical differences between males and females. It may be possible that females are limited by their pulmonary system to a greater degree than males. Perhaps these limitations attribute to a greater. V A / Q C inequality during exercise at both sub-max and maximal intensities. The contribution of a V A / Q C inequality throughout exercise has 19 been measured in males using the multiple inert gas elimination technique (Hopkins et al., 1994). It was determined that V A / Q C was the greatest contributor to a widened AaD02. E IAH in women has been associated with a widened A a D 0 2 at the onset of exercise (Harms et al., 1998; Wetter et al., 2001) although a diffusion limitation or V A / Q C inequality has not been directly measured. In addition to measuring V A / Q c , determining the hypoxic and hypercapnic ventilatory response amongst females during rest and exercise, may provide information into the realm of ventilatory response. Harms & Stager (1995) determined that, within males, a low hypoxic and hypercapnic ventilatory drive during exercise was related to EIAH. Alternately, other studies in males have shown that the resting hypoxic ventilatory response was not related to EIAH (Gavin et al, 1998; Hopkins & Mckenzie, 1989). However, this relationship has not been examined in females. Conclusion The prevalence of E I A H is slightly greater in women and occurs at a relatively lower VC^max as compared to males. Unlike males, EIAH was not correlated to aerobic capacity in women. It was proposed that an anatomical predisposition to expiratory flow limitation would lead to inspiratory muscle fatigue and subsequent EIAH. However, there was no significant decrease in post-exercise MIP. Sub-maximal hypoxemia is reported to occur in males and has been linked to a deficient hyperventilatory response (Rice et al, 1999; Aguilaniu et al, 2002) . Different patterns of desaturation were present amongst subjects and significant differences between fast and slow desaturators existed in breathing frequency, % SaC"2, and VE /VC0 2 ratios with fast desaturators possessing higher breathing frequencies, lower % S a 0 2 values, and higher VE /Vco 2 ratios. The specific cause of EIAH at sub-maximal exercise is yet unknown, however, evidence implicates ventilatory differences. Although not directly measured, the 2 0 observed ventilatory patterns of fast desaturators suggest a greater degree of dead space ventilation compared to the slow desaturators. It is unlikely that diffusion limitation plays a role during sub-max exercise (Hopkins et al, 1994), and flow limitation is more commonly observed during heavy and maximal exercise (McClaran etal, 1998; Walls et al, 2002). Slow desaturators can attribute their EIAH to a number of mechanisms, which together may compound the degree of hypoxemia. These mechanisms include diffusion limitation, mechanical constraint, or ventilation perfusion inequalities. 21 Table 1. Subject characteristics and resting pulmonary function data (N = 52). Mean ±SD ' Range % Predicted Age, yr 26.514.9 19-42 Height, cm 1.69 ±.06 1.54-1.82 Weight, kg 61.819.2 45 -93 FVC, litres 4.0 10.5 2.6-6.0 96.6 FEV, litres 3.5 10.4 2.6-4.6 106.4 FEV, /FVC % 86.8 ±4.7 78-98 ' 104.1 FEF 25-75% 3.8 10.7 2.6-6.0 96.6 M V V (12 sec), litres 151.4 128.8 102-213.8 125.6 Resting P E T C 0 2 ) mmHg 35.0 13.4 26.4-43.2 Legend: F V C = forced vital capacity F E V i = forced expiratory volume in 1 second F E V i / F V C % = percentage of F V C expired in F E V , F E F 25-75% = forced expiratory flow at 25-75 % of expiration (mid - flow) M V V = maximal voluntary ventilation during 12 seconds PETCO2 = partial pressure of end tidal C 0 2 22 Table 2. Subject physical characteristics and resting pulmonary function for non-, mild and moderate EIAH groups. Non EIAH (Sa0 2 = 98-95%) (n=17) Mild EIAH (Sa0 2 = 94-92%) (n=19) Moderate EIAH (Sa0 2 = 91-87%) (n=16) Age, yr 26.2 ±4 .3 28.3 ±5 .6 24.4 ± 4.2 Height, m 1.69 ± .08 1.68 ±.06 1.69 ±.05 Weight, kg 63.2 ± 12.3 60.0 ±7.2 ' 62.6 ± 7.51 FVC, litres 4.1 ±0.5 4.0 ±0.5 3.9 ±0.5 F E V i , litres 3.5 ±0 .4 3.5 ±0 .4 3.5 ± 0.4 FEV, / F V C , % 86.2 ± 5.2 85.7 ±3.8 88.6 ±5 .0 FEF 25-75% 3.8 ±0 .8 3.8 ±0.5 4.0 ±0 .7 M V V 12 sec, litres 150.2 ±29.3 143.7 ±24.3 150.2 ±29.2 Legend: FVC = forced vital capacity FEV, = forced expiratory volume in 1 second F E V , / F V C % = percentage of F V C expired in FEV, FEF 25-75% = forced expiratory flow at 25-75 % of expiration (mid - flow) M V V = maximal voluntary ventilation during 12 seconds 23 Table 3. Means of measured physiological variables of non, mild, and moderate EIAH Non EIAH (Sa0 2 = 98-95%) (n=17) Mild EIAH (Sa0 2 = 94-92%) (n=19) Moderate EIAH (Sa0 2 = 91-87 %) (n=16) VC^max, ml/kg/min 45.8 ±6.0 47.8 ±6.1 45.3 ±5.7 VChmax, 1/min 2.8 ±0.4 2.8 ±0.3 2.8 ±0.5 % SaC"2 at end exercise 97.4 ±0.8 • 93.3 ± 0 . 8 * 89.6 ±0.1 * Resting P E T C 0 2 , mmHg 35.0 ±3.3 35.6 ±3 .4 34.4 ±4.1 Max exercise PETCO2, mmHg 36.4 ±2.8 36.0 ±3.8 37.7 ±4.0 Resting VE, 1 / min 8.2 ± 1.9 8.0 ± 1.8 8.0 ± 1.7 Max VE, 1 / min 82.0 ±9.6 84.5 ± 15.1 83.6 ± 19.4 % M V V , 1 / min 45.1 ±8.6 39.6 ±9 .4 44.3 ±11.5 Pre-MIP, cmH 2 0 81.1 ± 13.9 75.9 ±20.7 79.5 ±30.5 Post-MIP, cmH 2 0 81.0 ± 16.7 75.4 ±18.3 77.0 ±27.1 Legend: %SaC>2 = % oxyhaemoglobin saturation at end exercise PETCO2 = partial pressure of end tidal CO2 during rest and maximal exercise VE / Max VE = minute ventilation at rest / maximal minute ventilation during exercise % M V V = percentage of maximal voluntary ventilation achieved during maximal exercise Pre / Post MIP = pre and post exercise maximal inspiratory mouth pressure * Significant differences between groups (p < .05) 24 Table 4. Means of measured physiological variables of Fast and Slow desaturators. Fast (n = 7) Slow (n = 28) VC^max ml/kg/min 44.5 ±6.1 47.8 ± 7.0 VE rest, 1/min 8.6 ± 1.5 8.5 ± 1.2 VE max, 1/min . 79.8 ± 19.0 89.2 ± 16.2 % M V V , l / m i n 47.6 ± 12.3 41.5 ±9 .0 Rest P E T C 0 2 ) mmHg 34.9 ± 1.7 36.0 ±2.8 End exercise P E T C O 2 , mmHg 35.1 ±4.6 37.5 ±3.9 Legend: VE rest = minute ventilation during resting conditions VE max = maximal minute ventilation achieved during maximal exercise % M V V = percentage of maximal voluntary ventilation (12 seconds) attained at maximal exercise. Rest PETCO2 = partial pressure of end tidal CO2 at rest End Exercise PETCO2 = partial pressure of end tidal CO2 at end of exercise 25 Table 5. Mean ± SD values of % Sa0 2 throughout exercise for non-, mild, and moderate EIAH groups. % S a 0 2 Non EIAH Mild EIAH Moderate EIAH (Sa0 2 = 98-95%) (Sa0 2 = 94-92 %) (Sa0 2 -91-87%) (n=17) (n=19) (n=16) Rest 97.8 ± 0.5 97.7 ± .04 98.0 ±0.5 Minute 1 96.3 ± 1.6 95.5 ±1.9 • 95.6 ±2.0 Minute 2 96.0 ±2.2 95.4 ±2.0 95.0 ±2.2 Minute 3 96.0 ±2 .4 95.2 ±1.8 95.0 ±2.4 Minute 4 95.7 ±2.0 95.3 ± 1.6 94.8 ±2.1 Minute 5 96.0 ± 1.4 95.4 ± 1.9 95.0 ±2.3 Minute 6 95.6 ±2.0 95.1 ±2.1 94.9 ±2.8 Minute 7 96.4 ± 1.1 95.3 ± 1.9 94.3 ±3.1 End Exercise 96.3 ± 1 . 2 * 92.7+1.5 * 89.6 ± 1.1 * significantly different between groups (p < .05) 26 Figure 1. Mean % SaC>2 values across time for non-, mild, and moderate EIAH groups Bars omitted for clarity, please refer to Table 5 for SD values. 100 ! 88 A 86 T r 1 1 1 1 1 1 1 Rest 1 2 3 4 5 6 7 END Time (min) Legend: (N = 52) • = non EIAH • = mild EIAH A = moderate EIAH * = significantly different between groups (p < .05) 27 Figure 2. Fast and slow desaturating groups % SaCh across time. Values are means ± SD Legend: • slow desaturators • fast desaturators * = significantly different between groups (p < .05) 28 Figure 3. Fast and slow desaturators VE across time . Values are means ± SD. 120 i Time (min) Legend: • = slow desaturators • = fast desaturators 29 Figure 4. Fast and Slow desaturators breathing frequency across time. Values are means ± SD. 60 -i 50 4 0 ~l 1 1 1 1 1 1 1 1 1 REST 1 2 3 4 5 6 7 END Time (min) Legend: • slow desaturators • fast desaturators * = significantly different between groups (p < .05) 30 Figure 5. Fast and Slow desaturators' tidal volume during exercise. Values are means ± SD. 2500 n Rest 1 2 3 4 5 6 7 END Time (min) Legend: • slow desaturators • fast desaturators 31 Figure 6. Fast and Slow desaturators VE /VC0 2 during exercise. Values are means ± SD: Legend: • slow desaturators • fast desaturators * = significantly different between groups (p < .05) Figure 7. Fast and Slow desaturating groups VE /Vo2 across time. Values are means ± SD. 50 n 45 -40 -15 -L 1 0 n ; 1 1 i 1 1 1 1 1 Rest 1 2 3 4 5 6 7 End Time (min) Legend: • slow desaturators • fast desaturators 33 Figure 8. Fast and Slow desaturators PETCO2 across time. Values are means ± SD. Legend • slow desaturators • fast desaturators 3 4 Figure 9. Percent oxyhaemoglobin saturation response to hyperoxic gas during exercise (n = 8) O (0 98 96 -\ 94 92 90 88 86 84 N o r m o x i a Hyperox ia Rest 1 3 4 5 6 Time (min) 8 End Legend • = mean%Sa02 values of hyperoxic test * = significantly different from rest (p < .05) Normoxia represents exercise at 80-85 % of peak power. The arrow represents the time point upon which hyperoxic gas (FIO2 26%) was administered. Hyperoxia represents exercise at 80-85 % of peak power while during which hyperoxic gas was utilized. 35 Figure 10. Percent oxyhaemoglobin saturation response to normoxia, hyperoxia, and return to normoxia during exercise (n = 3) 98 -, Time (min) Normoxia represents exercise at 80-85 % of peak power. The arrow represents the time point upon which hyperoxic gas (FIO2 26%) was administered. Hyperoxia represents exercise at 80-85 % of peak power while during which hyperoxic gas was utilized. . Normoxia at minute 9 represents removal of hyperoxic gas during exercise at 80-85 % of peak power. 36 APPENDIX A - LITERATURE REVIEW In response to whole-body exercise in a healthy individual, three physiological responses occur in order to meet the demands of exercise: 1) increased alveolar ventilation (VA) 2) increased cardiac output, and 3) redistribution of cardiac output to enhance perfusion of exercising muscles (Hlastala & Berger, 1996). The increased alveolar ventilation is brought about by an increased tidal volume and breathing frequency. As exercise progresses, the work of breathing increases because larger tidal volumes require more work to overcome the elastic recoil of the lungs and chest wall during inspiration (Levitsky, 1999). At maximal exercise, alveolar ventilation will increase from 5-6 1/min to 150 1/min (25 times) where cardiac output only increases 4-6 times its resting levels (Levitsky, 1999). The high flow rates associated with ventilation during heavy exercise result in a greater resistance of the airways. In order to prevent the respiratory muscles from becoming too taxed, the airway diameter is increased by neural (sympathetic stimulation) and passive mechanical components (Sheel, 2002). If the pulmonary system fails to support the demands of the cardiovascular system, then the exercising muscles will not receive the oxygenated blood they require in order to continue functioning at that level and exercise is ceased. During exercise, oxygen consumption can increase,up to 3-6 1/min depending on the fitness level of the subject. The diffusing capacity of the lung increases due to the increased volume of blood in the pulmonary capillaries and the increased diffusion capacity of the membrane (West, 2000). Gas moves through the conducting airways by bulk flow, which is governed by pressure differences. During bulk flow, gas moves from an area of high to low pressure. Once the gas meets the alveoli, movement occurs by diffusion, which is dependent upon a partial pressure gradient. Oxygen must dissolve in a liquid in order to pass through pulmonary surfactant, alveolar epithelium, interstitium, and capillary endothelium (Levitsky, 1999). Upon entering the bloodstream, the majority of oxygen enters the erythrocyte and combines with haemoglobin. Once again, oxygen is carried in the blood and delivered to the tissues via bulk 37 flow. Fick's law for diffusion determines the rate of diffusion of gas through the alveolar capillary barrier. Vgas = ( A » D « ( P r P 2 ) ) / T A = surface area of barrier D = diffusion coefficient T = thickness barrier or diffusion distance P1-P2 - partial pressure difference of gas across the barrier Any limitations to gas transfer can be attributed to the diffusion coefficient, barrier thickness, and the partial pressure difference (Levitsky, 1999). EIAH and Performance Exercise induced arterial hypoxemia (EIAH) has been defined as a decrease ,in arterial oxygen saturation levels of 3% or greater from baseline SaC*2 values of roughly 98% (Dempsey & Wagner, 1999). E IAH can be further categorized as mild (93-95%), moderate (88-93%), and severe (<88%) (Dempsey & Wagner, 1999). EIAH can have a significant detrimental affect on aerobic performance. In males, there is a linear relationship between the decline in SaC>2 and decrease in VC^max (r = 0.94) (Lawler et al, 1988). In females, it has been determined that for every 1% decline in arterial saturation below 3%, there is a 2% decline in VC^max (Harms et al, 2000). In addition to having a detrimental effect on performance, the incidence, of EIAH is quite high (-50%) in highly trained male athletes (Powers et al, 1988). Although the prevalence in males has been well documented, the prevalence in females is still unknown. Mechanisms The causes of hypoxemia have been extensively examined and there is no single definitive physiological mechanism (Dempsey & Wagner, 1999). The reported mechanisms thus far include: 1 Veno-arterial shunt 2. Ventilation perfusion mismatch (VA/QC) 3. Diffusion limitation 4. Relative alveolar hypoventilation 38 Veno-arterial shunts refer to blood which enters the arterial system without going through ventilated areas of lung (West, 2000). In the normal heart, some de-oxygenated venous blood drains into the left ventricle and mixes with arterial blood, decreasing arterial PO2. It is reported that shunts represent the decline of PO2 from 105 mmHg in the alveoli to 100 mmHg in the arterial blood (Levitsky, 1999). It has been concluded that shunts do not play a significant role in causing EIAH due to the fact that upon inhalation of hyperoxic gas (FI02 24%) during exercise, there is an increase in SaCh to normal values (Dempsey et al, 1984). If shunts were playing a significant role in arterial desaturation, then arterial hypoxemia would continue despite the inhalation of hyperoxic gas due to the continual existence of the shunt. . Diffusion limitation: The ability of oxygen to diffuse across the blood gas barrier is dependent upon four processes (West, 2000): 1. Red blood cell contact time in the pulmonary capillary bed 2. Diffusion capacity of the blood gas barrier to oxygen 3. Partial pressure difference of O2 across the membrane 4. Relative solubility of oxygen in alveolar wall tissue It is hypothesized that during maximal exercise, the volume of blood reaching the pulmonary capillaries reaches its morphological limit, henceforth the rate of blood flow increases to accommodate the large volumes of blood from the high cardiac output. The decreased time in the pulmonary capillary may lead to an inability of oxygen to saturate the haemoglobin molecule. Another mechanism that can lead to a diffusion limitation is pulmonary capillary stress failure (West et al, 1993). Stress failure of the capillary wall is believed to be due to the increased pulmonary micro vascular pressure from high blood volumes. The rupture can lead to fluid accumulation in the interstitium and the alveoli resulting in interstitial and pulmonary oedema. There is no direct evidence of a capillary stress failure in humans however, there is some evidence that a pulmonary oedema may be present. Hopkins et al. (1997) showed an 39 increase in red blood cells, total protein, and albumin in highly trained male athletes (n = 6) following a short bout of heavy exercise compared to inactive controls (n = 4). The researchers failed to find significant differences between groups in cytokine content and activators of inflammatory pathways. The authors concluded that an altered blood-gas barrier is due to mechanical stress (i.e. increased capillary pressure)(Hopkins et al, 1997). However, the researchers did not record arterial saturation in the exercising athletes exhibiting capillary stress failure. In addition, some elite male subjects have shown EIAH at sub-maximal levels making stress-failure an unlikely cause of EIAH (Powers et al, 1988; Dempsey & Wagner, 1999). Pulmonary oedema is believed to occur through an immune mediated reaction. During heavy workloads, some athletes show an increased release of histamine. Anselme et al.(1994) report a positive correlation between % histamine release and the drop in PaC^. Histamine is a marker of inflammation that can be found in basophiles, a type of leukocyte. Cytokines posses the ability to react with basophiles and induce histamine release. There is evidence that athletes show increased levels of the cytokines interleukin-lbeta (IL-1B) at all times and interleukin-8 (IL-8) in response to exercise (Mucci et al, 1999; Mucci et al, 2000; Moldoveanu et al, 2001). However, Hopkins et al. (1997) failed to find any differences in inflammatory mediators and cytokine content in male athletes exhibiting an altered blood-gas barrier following a maximal exercise bout compared to inactive controls. Although there is evidence that some athletes show increased fluid accumulation and markers of inflammation during maximal exercise, it is unlikely that an immune mediated pulmonary oedema is responsible for causing EIAH. In a study using horses, the animals performed a maximal exercise test where they exhibited EIAH and showed evidence of pulmonary oedema. After rest, the horses performed an additional bout of maximal exercise and they failed to show a worsened hypoxemic response. In some cases, the second test showed a decreased hypoxemic response (Manohar et al, 2001). In a study by St. Croix et al. (1998) 28 females performed an incremental treadmill test to V02max and then completed a constant load test to exhaustion following a rest period. A l l subjects showed a narrowed A-aDo2 and an 40 increase in Pao2 following the second exercise bout compared to the end point of the initial incremental test (St Croix et al, 1998). Therefore, EIAH was lessened by prior exercise. These studies support a mechanism that may be present only during the exercise period (St Croix et al, 1998; Manohar et al, 2001). Ventilation perfusion inequality (VA/Qc) results when there is an imbalance between ventilation and blood flow in various regions of the lung. An imbalance of the V A /Qc ratio leads to impaired transfer of O2 and CO2 (West, 2000). The apex of the lung is not as well ventilated and is underperfused with pulmonary blood flow at rest as compared to the base of the lung (Levitsky, 1999). Hammond et al. (1986) showed that during heavy exercise, V A /Qc inequality increased with rising VO2 levels. It has been estimated that 60% of the increased alveolar-arterial (A-a DO2) difference can be attributed to a ventilation perfusion inequality. Relative Alveolar Hypoventilation. Some, but not all hypoxemic athletes have exhibited a decreased drive to breathe during exercise. Some individuals have decreased chemo responsiveness to increasing CO2 and decreasing pH and O2 levels. Hopkins and McKenzie (1989) showed no significant differences between desaturating aerobic and anaerobic male athletes hypoxic ventilatory response. That is to say, their ventilatory response to isocapnic hypoxia was not related to their arterial desaturation. Alternately, other studies have found evidence that correlates a decreased ventilatory response and EIAH (Harms & Stager, 1995; Gavin et al, 1998). Although this mechanism is possible, further research is needed. Respiratory muscle fatigue. Respiratory muscle fatigue can be defined as an inability of the respiratory muscles to continue to develop sufficient respiratory pressure swings to maintain normal alveolar ventilation (Grassino & Macklem, 1984). The site of fatigue can occur anywhere between the brain and periphery (brain, spinal cord, peripheral nerve, neuromuscular junction, muscle cell membrane, transverse tubular system, calcium release, actin-myosin activation, cross-bridge formation) (Roussos et al, 1979). The site of fatigue determines whether it is central (central nervous system) or peripheral (neuromuscular junction or within the muscle itself). It is important to determine if the respiratory command 41 center becomes fatigued and fails to deliver a signal to contract or the subject is no longer motivated (central) or i f the periphery is unable to fulfill the command (peripheral). It has been shown that unloading of the respiratory muscles during heavy exercise (>90-95% of VChmax) can improve exercise time (Johnson et al, 1996) and reduce the work of breathing (40-50%) and whole body V 0 2 (10-15%) at 80-85% V0 2 max (Babcock et al, 2002). In addition, fatigue of the inspiratory muscles has been shown to cause a decrease in cardiac output to the resting limb and an increase in limb muscle sympathetic nerve activity, leading to limb vasoconstriction (Harms et al, 1997; St Croix et al, 2000; Sheel et al, 2001). This evidence supports the hypothesis that there is a competition for a finite cardiac output between the inspiratory muscles and the other skeletal muscles. During maximal exercise, blood may become diverted to the periphery to a greater degree than to the diaphragm. Without an adequate oxygen supply, the diaphragm muscle may become fatigued, resulting in decreased alveolar ventilation. Johnson et al. (1992) showed that the relative contribution of the diaphragm to total respiratory motor output decreased with exercise duration. The authors concluded that diaphragmatic fatigue was caused by the ventilatory requirements imposed by heavy exercise. There are a number of ways to detect the presence of diaphragm fatigue. One method is the measurement of maximal inspiratory pressure (MIP) from the mouth. Decreases in post-exercise MIP detect the presence of global inspiratory muscle fatigue. Decreases in post-exercise MIP are found following marathon running and triathlon performance (Loke et al, 1982; Hil l et al, 1991). Coast et al. (1990) compared highly trained cross country skiers (n = 6) and sedentary subjects (n = 5) following a maximal incremental cycle ergometer test and found that only the sedentary subjects had a decline in post-exercise MIP. Mechanical restraint is seen during expiration whereby narrow airways cause resistance to expired airflow. As exercise intensity increases, the tidal volume and breathing frequency increase, causing an increase in the end expiratory lung volume (EELV). Inspiratory volume begins to approach total lung capacity (TLC) and lung hyperinflation becomes present 42 (Johnson et al, 1996; McClaran et al, 1998; Dempsey & Wagner, 1999; McClaran et al, 1999). Lung hyperinflation causes a disturbance of the length-tension relationship of the inspiratory muscles, predominately the diaphragm, by increasing the inspiratory elastic load (Johnson et al, 1996). To continue contractions from a less optimal length, the work required of the muscles increases, resulting in an increased VO2. Recently it has been shown that unloading the respiratory muscles during exercise can decrease whole body VO2 10-15% (Babcock et al, 2002). It is possible that a mechanical restraint can lead to inspiratory muscle fatigue. Studies have shown that the work of breathing required during maximal exercise is not fatiguing on its own, but combined with whole-body exercise can induce diaphragm fatigue (Bai et al, 1984; Babcock et al, 1995b). Gender Differences The incidence of EIAH in male elite athletes has been determined to be approximately 50% (Powers et al, 1988). The studies that have been done on females report conflicting results. Hopkins et al. (2000) state that there is no significant difference between the incidence of EIAH in males and females. This study compared running and cycling V0 2 max tests and determined that only females with a VC^max that was 150% greater than their predicted VO2 exhibited EIAH. Harms et al. (1998) used a somewhat larger female population with a greater range of V0 2 max values and showed that females who's VO2 was within 15% of their predicted, were able to desaturate. To date, the Harms et al. study has used the largest female population of 29 and its subject pool included habitually active subjects with VC^max values in the 30ml/kg/min range. 43 Table 6. EIAH studies with female subjects Author Variable measured Total Subjects # Who Became Hypoxaemic Walls et al. 2002 3-5 K m runs while measuring flow limitation 8 8 (100%) Wetter et al. 2001 Run to exhaustion at 95% V0 2 max 17 7 (41%) Hopkins et al. 2000 Fast and slow incremental protocols of running and cycling to exhaustion. 17 4 (24%) (150% of . predicted V 0 2 ) Harms et al. 1998 2 treadmill tests 29 22 (76%) Vi of 22 hypoxic subjects had V 0 2 w / i n 15% of predicted McClaran et al. 1998 Expiratory flow limitation. 29 **Same subjects as Harms et al. 1997 study Females may have a higher prevalence of EIAH than males. Anatomical differences between the two sexes exist and whether these differences can account for a greater prevalence is unknown. These physiological differences include; smaller lung diffusion surface, smaller lung size, and smaller airways in females when compared to age, height, and weight matched males (Thurlbeck, 1982). Smaller airways contribute to expiratory flow resistance during exercise, which may lead to an expiratory flow limitation. The result of an expiratory flow limitation is a hindered length-tension relationship of the inspiratory muscles, predominately the diaphragm. The work required of the inspiratory muscles increases and combined with maximal exercise may lead to their fatigue (Bai et al, 1984). Recently a study by Walls et al. (2002) measured 8 women with a VC^max range between 42-52 ml/kg/min and found that all subjects exhibited EIAH and that there was a strong correlation between EIAH and expiratory flow limitation (r = 0.71). In addition, the diaphragm can compete with other skeletal muscles during maximal exercise (Harms et al, 1997; St Croix et al, 2000). If the blood supply to the diaphragm is inadequate to meet the ventilatory demands, fatigue of the inspiratory muscles can ensue. 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Effects of exhaustive edurance exercise on pulmonary gas exchange and airway function in women. J Appl Physiol 91. 55 APPENDIX B : STATISTICAL ANALYSES AND INDIVIDUAL GROUP DATA Table 7. Repeated Measures A N O V A for P E T C 0 2 , VE , and V 0 2 (ml/kg), V 0 2 (1/min), V e / V 0 2 , and V e / V C 0 2 on non, mild, and moderate EIAH measured throughout exercise 7 - A. P E T C 0 2 (mmHg) Tests of Within-Subjects Effects Measure: MEASURE 1 Type III Sum Source of Squares df Mean Square F Sig. PETC02 Sphericity Assumed 633.181 4 158.295 27.493 .000 Greenhouse-Geisser 633.181 2.297 275.689 27.493 .000 Huynh-Feldt 633.181 2.519 251.348 27.493 .000 Lower-bound 633.181 1.000 633.181 27.493 .000 P ETC 02 * Sphericity Assumed 43.290 8 5.411 .940 .485 GROUP Greenhouse-Geisser 43.290 4.593 9.424 .940 .453 Huynh-Feldt 43.290 5.038 8.592 .940 .458 Lower-bound 43.290 2.000 21.645 .940. .398 Error(CO) Sphericity Assumed 1105.482 192 5.758 Greenhouse-Geisser 1105.482 110.243 10.028 Huynh-Feldt 1105.482 120.919 9.142 Lower-bound 1105.482 48.000 23.031 Tests of Between-Subjects Effects Measure: MEASUREJ Transformed Variable: Average . Source Type III Sum of Squares df Mean Square F Sig. Intercept 360927.217 1 360927.217 9713.042 .000 GROUP 20.706 2 10.353 .279 .758 Error 1783.633 48 37.159 5 6 7 - B. V E (1/min) Tests of Within-Subjects Effects Measure: MEASURE 1 Source Type III Sum of Squares df Mean Square F Sig. Ve Sphericity Assumed 193446.331 8 24180.791 90.280 .000 Greenhouse-Geisser 193446.331 1.310 147655.257 90.280 .000 Huynh-Feldt 193446.331 1.387 139512.256 90.280 .000 Lower-bound 193446.331 1.000 193446.331 90.280 .000 Ve * GROUP Sphericity Assumed 3943.616 16 246.476 .920 .546 Greenhouse-Geisser 3943.616 2.620 1505.057 .920 .426 Huynh-Feldt 3943.616 2.773 1422.055 .920 .430 Lower-bound 3943.616 2.000 1971.808 .920 .405 Error(VENT) Sphericity Assumed 104994.243 392 267.842 Greenhouse-Geisser 104994.243 64.196 1635.527 Huynh-Feldt 104994.243 67.943 1545.330 Lower-bound 104994.243 49.000 2142.740 Tests of Between-Subjects Effects Measure: MEASUREJ Transformed Variable: Average Source Type III Sum of Squares df Mean Square F Sig. Intercept 618299.763 1 618299.763 1632.655 .000 GROUP 299.843 2 149.921 .396 .675 Error 18556.700 49 378.708 57 7 - C. V 0 2 (1/min) Tests of Within-Subjects Effects Measure: MEASURE 1 Source Type III Sum of Squares df Mean Square F Sig. V 0 2 ml Sphericity Assumed 133867449 8 16733431.11 602.341 .000 Greenhouse-Geisser 133867449 2.425 55210734.13 602.341 .000 Huynh-Feldt 133867449 2.738 48889444.79 602.341 .000 Lower-bound 133867449 1.000 133867448.9 602.341 .000 V02 ml * Sphericity Assumed 191387.023 16 11961.689 .431 .974 GROUP Greenhouse-Geisser 191387.023 4.849 39466.719 .431 .821 Huynh-Feldt 191387.023 5.476 34948.023 .431 .842 Lower-bound 191387.023 2.000 95693.511 .431 .653 Error(V02) Sphericity Assumed 8445322.294 304 27780.665 Greenhouse-Geisser 8445322.294 92.137 91660.277 Huynh-Feldt 8445322.294 104.050 81165.739 Lower-bound 8445322.294 38.000 222245.324 Tests of Between-Subjects Effects Measure: MEASUREJ Transformed Variable: Average Source Type III Sum of Squares df Mean Square F Sig. Intercept 694255721 1 694255720.6 4092.721 .000 GROUP 295671.714 2 147835.857 .872 .427 Error 6446008.771 38 169631.810 58 7 - D. VE rvo2 Tests of Within-Subjects Effects Measure: MEASURE 1 Source Type III Sum of Squares df Mean Square F Sig. VEA/02 Sphericity Assumed 6083.838 8 760.480 50.897 .000 Greenhouse-Geisser 6083.838 2.640 2304.902 50.897 .000 Huynh-Feldt 6083.838 2.924 2080.945 50.897 .000 Lower-bound 6083.838 1.000 6083.838 50.897 .000 VE/V02 * VAR00001 Sphericity Assumed 208.456 16 13.029 .872 .602 Greenhouse-Geisser 208.456 5.279 39.488 .872 .507 Huynh-Feldt 208.456 5.847 35.651 .872 .515 Lower-bound 208.456 2.000 104.228 .872 .425 Error(VEA/02) Sphericity Assumed 5737.585 384 14.942 Greenhouse-Geisser 5737.585 126.697 45.286 Huynh-Feldt 5737.585 140.332 40.886 Lower-bound 5737.585 48.000 119.533 Tests of Between-Subjects Effects Measure: MEASURE_1 Transformed Variable: Average Source Type III Sum of Squares df Mean Square F Sig. Intercept 246809.998 1 246809.998 2546.681 .000 groups 1.557 2 .779 .008 .992 Error 4651.891 48 96.914 59 7 - E. VE / V C 0 2 Tests of Within-Subjects Effects Measure: MEASURE 1 Source Type III Sum of Squares df Mean Square F Sig. VEA/C02 Sphericity Assumed 4563.701 8 570.463 6.605 .000 Greenhouse-Geisser 4563.701 1.199 3806.560 6.605 .009 Huynh-Feldt 4563.701 1.262 3615.164 6.605 .008 Lower-bound 4563.701 1.000 4563.701 6.605 .013 VEA/C02 * groups Sphericity Assumed 1330.889 16 83.181 .963 .497 Greenhouse-Geisser 1330.889 2.398 555.044 .963 .401 Huynh-Feldt 1330.889 2.525 527.136 .963 .404 . Lower-bound 1330.889 2.000 665.444 .963 .389 Error(VE/VC02) Sphericity Assumed 33858.450 392 86.374 Greenhouse-Geisser 33858.450 58.746 576.350 Huynh-Feldt 33858.450 61.856 547.371 Lower-bound 33858.450 49.000 690.989 Tests of Between-Subjects Effects Measure: MEASURE_1 Transformed Variable: Average Source Type III Sum of Squares df Mean Square F Sig. Intercept 310180.309 1 310180.309 3724.186 .000 groups 82.814 2 41.407 .497 .611 Error 4081.116 49 83.288 60 Table 8. Pearson product moment correlation of all subjects (n = 52) during exercise Correlations GROUP S A 0 2 V 0 2 P E T C 0 2 GROUP Pearson Correlation 1 -.906** -.055 .151 Sig. (2-tailed) .000 .698 .289 N 52 52 52 51 % S A 0 2 Pearson Correlation - . 9 0 6 " 1 .098 -.175 at end Sig. (2-tailed) .000 .491 .218 exercise • N 52 >52 52 51 V 0 2 Pearson Correlation -.055 .098 1 .318* ml/kg Sig. (2-tailed) .698 .491 .023 N 52 52 52 51 PETCO Pearson Correlation .151 -.175 .318* 1 2 at end Sig. (2-tailed) .289 .218 .023 exercise N 51 51 51 51 • Correlation is significant at the 0.01 level (2-tailed). *• Correlation is significant at the 0.05 level (2-tailed). Table 9. Pearson product moment correlations of physiological variables measured during exercise (non, mild, moderate EIAH groups) Non EIAH Correlations NON V02 NON VE NON SA N0N_V02 Pearson Correlation 1 .934" -.524 Sig. (2-tailed) .000 .148 N 9 9 9 NON_VE Pearson Correlation .934" 1 -.651 Sig. (2-tailed) .000 .058 N 9 9 9 non Sa02 Pearson Correlation -.524 -.651 1 Sig. (2-tailed) .148 .058 N 9 9 9 • Correlation is significant at the 0.01 level (2-tailed). Mild EIAH Correlations MILD V 0 2 MILD VE MILD SA MILD_ V 0 2 Pearson Correlation 1 . 9 5 3 " - . 8 8 5 " Sig. (2-tailed) .000 .002 N 9 9 9 MILD_ VE Pearson Correlation .953" 1 - . 8 0 8 " Sig. (2-tailed) .000 .008 N 9 9 9 MILD Pearson Correlation - . 8 8 5 " - . 8 0 8 " 1 Sa02 Sig. (2-tailed) .002 .008 N 9 9 9 '• Correlation is significant at the 0.01 level (2-tailed). Moderate EIAH Correlations MOD V 0 2 MOD VE MOD SA MOD. V 0 2 Pearson Correlation .1 . 9 6 6 " - . 9 1 6 " Sig. (2-tailed) .000 .001 N 9 9 9 MOD. VE Pearson Correlation . 9 6 6 " 1 - . 9 4 9 " Sig. (2-tailed) .000 .000 N 9 9 9 MOD Pearson Correlation - . 9 1 6 " - . 9 4 9 " 1 Sao2 Sig. (2-tailed) .001 .000 N 9 9 9 **• Correlation is significant at the 0.01 level (2-tailed). FAST A N D S L O W G R O U P S Table 10. Repeated measures A N O V A for fast and slow desaturators VE, Vt, Fb, Sa02, V0 2(l/min), V 0 2 (ml/kg), P E T C 0 2 , V e / V 0 2 , and V e / V C 0 2 during exercise. 1 0 - A . VE (1/min) Tests of Within-Subjects Effects Measure: MEASURE_1 Type III Sum Source of Squares df Mean Square F Sig. Ve Sphericity Assumed 84915.072 8 10614.384 252.514 .000 Greenhouse-Geisser 84915.072 1.860 45663.250 252.514 .000 Huynh-Feldt 84915.072 2.026 41915.793 252.514 .000 Lower-bound 84915.072 1.000 84915.072 252.514 .000 Ve * GROUP Sphericity Assumed 986.833 8 123.354 2.935 .004 Greenhouse-Geisser 986.833 1.860 530.672 2.935 .064 Huynh-Feldt 986.833 2.026 487.121 2.935 .059 Lower-bound 986.833 1.000 986.833 2.935 .096 ErrorfVE) Sphericity Assumed 11097.178 264 42.035 Greenhouse-Geisser 11097.178 61.367 180.834 Huynh-Feldt 11097.178 66.853 165.994 Lower-bound 11097.178 33.000 336.278 Tests of Between-Subjects Effects Measure: MEASURE_1 Transformed Variable: Average Source Type III Sum of Squares df Mean Square F Sig. Intercept 268509.189 1 268509.189 1403.672 .000 GROUP 80.581 1 80.581 .421 .521 Error 6312.590 33 191.291 63 10 - B. Tidal Volume (Vt (ml)) Tests of Within-Subjects Effects Measure: MEASURE_1 Type III Sum Source of Squares df Mean Square' F Sig. Vt Sphericity Assumed 55336266.0 8 6917033.254 16.664 .000 Greenhouse-Geisser 55336266.0 1.082 51138802.19 16.664 .000 Huynh-Feldt 55336266.0 1.124 49235599.86 16.664 .000 Lower-bound . 55336266.0 1.000 55336266.03 16.664 .000 Vt * GROUP Sphericity Assumed 12533186.9 8 1566648.357 3.774 .000 Greenhouse-Geisser 12533186.9 1.082 11582497.51 3.774 .057 Huynh-Feldt 12533186.9 1.124 11151438.60 3.774 .055 Lower-bound 12533186.9 1.000 12533186.85 '3.774 .061 Error(FACTORI) Sphericity Assumed 109582489 264 415085.184 Greenhouse-Geisser 109582489 35.709 3068795.295 Huynh-Feldt 109582489 37.089 2954585.769 Lower-bound 109582489 33.000 3320681.470 Tests of Between-Subjects Effects Measure: MEASURE_1 Transformed Variable: Average Source Type III Sum of Squares df Mean Square F Sig. Intercept 368958235 1 368958235.0 504.030 .000 GROUP 24494.905 1 24494.905 .033 .856 Error 24156552.9 33 732016.756 64 10 - C. Breathing Frequency Tests of Within-Subjects Effects Measure: MEASURE_1 Type III Sum Source of Squares df Mean Square F Sig. Fb Sphericity Assumed 18174.671 8 2271.834 99.761 .000 Greenhouse-Geisser 18174.671 3.139 5790.536 99.761 .000 Huynh-Feldt ; 18174.671 3.612 5031.984 99.761 .000 Lower-bound 18174.671 1.000 18174.671 99.761 .000 F b * G R O U P Sphericity Assumed • 323.700 8 40.462 1.777 .082 Greenhouse-Geisser 323.700 3.139 103.132 1.777 .154 Huynh-Feldt .. 323.700 3.612 89.622 1.777 .144 Lower-bound 323.700 1.000 323.700 1.777 .192 Error(FACTORI) Sphericity Assumed 6012.008 264 22.773 Greenhouse-Geisser 6012.008 103.577 58.044 Huynh-Feldt 6012.008 119.190 50.440 Lower-bound 6012.008 33.000 182.182 Tests of Between-Subjects Effects Measure: M E A S U R E J Transformed Variable: Average Type III Sum Source of Squares df Mean Square F Sig. Intercept 154479.645 1 154479.645 848.222 .000 GROUP 1317.645 1 1317.645 7.235 .011 Error 6010.019 33 182.122 65 10 - D. % Sa0 2 Tests of Within-Subjects Effects Measure: M E A S U R E J Type III Sum Source of Squares df Mean Square F Sig. % S a 0 2 Sphericity Assumed 560.216 8 70.027 44.315 .000 Greenhouse-Geisser 560.216 3.439 162.879 44.315 .000 Huynh-Feldt 560.216 4.005 139.889 44.315 .000 Lower-bound 560.216 1.000 560.216 44.315 .000 % S a 0 2 * GROUP Sphericity Assumed 121.486 8 15.186 9.610 .000 Greenhouse-Geisser 121.486 3.439 35.321 9.610 .000 Huynh-Feldt 121.486 4.005 30.336 9.610 .000 Lower-bound 121.486 1.000 121.486 9.610 .004 Error(FACTOR1) Sphericity Assumed 417.175 264 1.580 Greenhouse-Geisser 417.175 113.502 3.675 Huynh-Feldt 417.175 132.155 3.157 Lower-bound 417.175 33.000 12.642 Tests of Between-Subjects Effects Measure: M E A S U R E J Transformed Variable: Average Source Type III Sum of Squares df Mean Square F Sig. Intercept 1786454.870 1 1786454.870 230313.8 .000 G R O U P 513.029 1 513.029 66.141 .000 Error 255.968 33 7.757 10 - E . V o 2 (1/min) Tests of Within-Subjects Effects Measure: MEASURE 1 Type III Sum Source of Squares df Mean Square F Sig. V02 Sphericity Assumed 83501895.7 8 10437736.97 415.778 .000 Greenhouse-Geisser 83501895.7 2.684 31106465.48 415.778 .000 Huynh-Feldt 83501895.7 3.033 27529201.28 415.778 .000 Lower-bound 83501895.7 1.000 83501895.75 415.778 .000 V 0 2 * Sphericity Assumed 831494.359 8 103936.795 4.140 .000 GROUP Greenhouse-Geisser 831494.359 2.684 309751.657 4.140 .011 Huynh-Feldt 831494.359 3.033 274130.011 4.140 .008 Lower-bound 831494.359 1.000 831494.359 4.140 .050 Error(V) Sphericity Assumed 6627477.817 264 25104.083 Greenhouse-Geisser 6627477.817 88.585 74814.999 Huynh-Feldt 6627477.817 100.096 66211.224 Lower-bound 6627477.817 33.000 200832.661 Tests of Between-Subjects Effects Measure: MEASURE 1 Transformed Variable: Average Source Type III Sum of Squares • df Mean Square F Sig. Intercept 452246811 1 452246810.7 2937.482 .000 GROUP 697975.143 • 1 697975.143 4.534 .041 Error 5080590.745 33 153957.295 4 n 3.5 1 0 J ^ , , ^ - , , , , Rest 1 2 3 4 5 6 7 END Time (min) • = fast desaturators •= slow desaturators * = significant difference between groups 67 10 - F. V 0 2 (ml/kg) Tests of Within-Subjects Effects Measure: MEASURE 1 Type III Sum Source of Squares df Mean Square F Sig. FACTOR1 Sphericity Assumed 24795.578 8 3099.447 557.005 .000 Greenhouse-Geissei 24795.578 2.302 10768.992 557.005 .000 Huynh-Feldt 24795.578 2.560 9685.550 557.005 .000 Lower-bound 24795.578 1.000 24795.578 557^.005 .000 FACTOR1 * GROUI Sphericity Assumed 109.381 8 13.673 2.457 .014 Greenhouse-Geissei 109.381 2.302 47.506 2.457 .085 Huynh-Feldt 109.381 2.560 42.726 2.457 .078 Lower-bound 109.381 1.000 109.381 2.457 .127 Error(FACTORI) Sphericity Assumed 1469.024 264 5.564 Greenhouse-Geissei 1469.024 75.982 19.334 Huynh-Feldt 1469.024 84.482 17.389 Lower-bound 1469.024 33.000 44.516 Tests of Between-Subjects Effects Measure: MEASURE_1 Transformed Variable: Average Type III Sum Source of Squares df Mean Square F Sig. Intercept 137408.533 1 137408.533 1734.644 .000 GROUP 90.895 1 90.895 1.147 .292 Error 2614.070 33 79.214 60 -i 50 -\ • = fast desaturators •= slow desaturators 68 1 0 - G . PETC0 2 (mmHg) Tests of Within-Subjects Effects Measure: MEASURE 1 Type III Sum Source of Squares df Mean Square F Sig. PETC02 Sphericity Assumed 118.320 4 29.580 1.726 .148 Greenhouse-Geisser 118.320 1.913 61.863 1.726 .188 Huynh-Feldt 118.320 2.101 56.313 1.726 .185 Lower-bound 118.320 1.000 118.320 1.726 .199 PETC02 * GROUP Sphericity Assumed 23.384 4 5.846 .341 .850 Greenhouse-Geisser 23.384 1.913 12.226 .341 .703 Huynh-Feldt 23.384 2.101 11.129 .341 .723 Lower-bound 23.384 1.000 23.384 .341 .563 Error(FACTORI) Sphericity Assumed 2125.453 124 17.141 Greenhouse-Geisser 2125.453 59.291 35.848 Huynh-Feldt 2125.453 65.135 32.632 Lower-bound 2125.453 31.000 68.563 Tests of Between-Subjects Effects Measure: M E A S U R E J Transformed Variable: Average Source Type III Sum of Squares df Mean Square F Sig. Intercept 135497.219 . 1 135497.219 4187.981 .000 GROUP 79.906 1 79.906 2.470 .126 Error 1002.969 31 32.354 45 I -UJ 30 -25 -I , , : , , • 1 1 REST 50W 100W 150W 200W End Time • = fast desaturators •= slow desaturators 69 10 - H. VE / V 0 2 Tests of Within-Subjects Effects Measure: MEASURE 1 Type III Sum Source of Squares df Mean Square F Sig. VE/V02 Sphericity Assumed 3188.243 8 398.530 23.882 .000 Greenhouse-Geisser 3188.243 2.836 1124.184 23.882 .000 Huynh-Feldt 3188.243 3.224 988.775 23.882 .000 Lower-bound 3188.243 1.000 3188.243 23.882 .000 VE/V02 * GROUP Sphericity Assumed 76.097 8 9.512 .570 .802 Greenhouse-Geisser 76.097 2.836 26.832 .570 .627 Huynh-Feldt 76.097 3.224 23.600 .570 .648 Lower-bound 76.097 1.000 76.097 .570 .456 Error(VE_V02) Sphericity Assumed 4405.524 264 16.688 Greenhouse-Geisser 4405.524 93.590 47.073 Huynh-Feldt 4405.524 106.406 41.403 Lower-bound 4405.524 33.000 133.501 Tests of Between-Subjects Effects Measure: M E A S U R E J Transformed Variable: Average Source Type III Sum of Squares df Mean Square F Sig. Intercept 112599.485 1 112599.485 1160.209 .000 GROUP 88.741 1 88.741 .914 .346 Error 3202.684 33 97.051 > -15 -10 -I , , , , , , , ' i 1 Rest 1 2 3 4 5 6 7 End Time (min) • = fast desaturators •= slow desaturators 10 -1. VE/VCO2 Tests of Within-Subjects Effects M e a s u r e : M E A S U R E J T y p e I I I S u m S o u r c e o f S q u a r e s d f M e a n S q u a r e F S i g . V E / V C 0 2 S p h e r i c i t y A s s u m e d 2 0 4 0 . 7 0 8 8 2 5 5 . 0 8 9 3 4 . 6 9 5 , 0 0 0 G r e e n h o u s e - G e i s s e r 2 0 4 0 . 7 0 8 1 . 9 3 1 1 0 5 7 . 0 7 1 3 4 . 6 9 5 . 0 0 0 -H u y n h - F e l d t 2 0 4 0 . 7 0 8 . 2 . 1 1 0 9 6 6 . 9 8 4 3 4 . 6 9 5 . 0 0 0 L o w e r - b o u n d 2 0 4 0 . 7 0 8 1 . 0 0 0 2 0 4 0 . 7 0 8 3 4 . 6 9 5 . 0 0 0 V E A / C 0 2 * G R O U P S p h e r i c i t y A s s u m e d 1 6 . 2 1 2 8 2 . 0 2 6 . 2 7 6 . 9 7 3 G r e e n h o u s e - G e i s s e r 1 6 . 2 1 2 1 . 9 3 1 8 . 3 9 8 . 2 7 6 . 7 5 2 H u y n h - F e l d t 1 6 . 2 1 2 2 . 1 1 0 7 . 6 8 2 . 2 7 6 . 7 7 2 L o w e r - b o u n d 1 6 . 2 1 2 1 . 0 0 0 . 1 6 . 2 1 2 . 2 7 6 . 6 0 3 E r r o r ( V E _ V C 0 2 ) S p h e r i c i t y A s s u m e d ' 1 9 4 0 . 9 9 9 2 6 4 7 . 3 5 2 G r e e n h o u s e - G e i s s e r 1 9 4 0 . 9 9 9 6 3 . 7 0 8 3 0 . 4 6 7 H u y n h - F e l d t 1 9 4 0 . 9 9 9 6 9 . 6 4 3 2 7 . 8 7 1 L o w e r - b o u n d 1 9 4 0 . 9 9 9 3 3 . 0 0 0 5 8 . 8 1 8 Tests of Between-Subjects Effects M e a s u r e : M E A S U R E J T r a n s f o r m e d V a r i a b l e : A v e r a g e S o u r c e T y p e I I I S u m o f S q u a r e s d f M e a n S q u a r e F S i g . I n t e r c e p t 1 3 8 6 9 5 . 8 2 0 1 1 3 8 6 9 5 . 8 2 0 3 0 1 1 . 8 2 8 . 0 0 0 G R O U P 2 7 7 . 2 3 2 1 2 7 7 . 2 3 2 6 . 0 2 0 . 0 2 0 E r r o r 1 5 1 9 . 6 6 2 3 3 4 6 . 0 5 0 V E / V C 0 2 40 -, 15 -10 -I : 1 1 1 1 1 1 1 1 1 Rest 1 2 3 4 5 6 7 End • = fast desaturators •= slow desaturators * = significant difference between groups Table 11. A N O V A of variables between groups to determine where significant differences occurred. 11-A V 0 2 (1/min) ANOVA Sum of Squares df Mean Square F Sig. REST Between Groups 376.216 1 376.216 .136 .715 Within Groups 91455.277 33 2771.372 Total 91831.493 34 V02 Between Groups 65968.007 1 65968.007 2.368 .133 Within Groups 919209.0 33 27854.817 Total 985177.0 34 V02_2 Between Groups 7475.207 1 7475.207 .376 .544 Within Groups 655994.4 33 19878.618 Total 663469.6 34 V02_3 Between Groups 36289.400 1 36289.400 1.662 .206 Within Groups 720525.6 33 21834.108 Total 756815.0 34 V02_4 Between Groups 45865.400 1 45865.400 2.837 .102 Within Groups 533549.6 33 16168.169 Total 579415.0 34 V02_5 Between Groups 1504.864 1 1504.864 .019 .891 Within Groups 2608018 33 79030.843 Total 2609523 34 V02_6 Between Groups 71370.864 1 71370.864 2.955 .095 Within Groups 796971.8 33 24150.661 Total 868342.7 34 V02_7 Between Groups 120071.4 1 120071.429 7.846 .008 Within Groups 505025.7 33 15303.810 Total 625097.1 34 END Between Groups 1180548 1 1180548.114 7.988 .008 Within Groups 4877319 33 147797.558 Total 6057868 34 72 1 1 - B V 0 2 (ml/kg) ANOVA Sum of Squares df Mean Square F Sig. REST V 0 2 ml/kg Between Groups . Within Groups Total 2.323 50.729 53.052 1 33 34 2.323 1.537 1.511 .228 V 0 2 1 Between Groups 2.554 1 2.554 .227 .637 Within Groups 371.669 33 11.263 Total 374.222 34 V 0 2 2 Between Groups 24.055 1 24.055 . 2.985 .093 Within Groups 265.900 33 8.058 Total 289.956 34 V 0 2 3 Between Groups 14.843 1 14.843 1.514 .227 Within Groups 323.519 33 9.804 Total 338.362 34 V 0 2 4 Between Groups 24.515 1 24.515 2.219 .146 Within Groups 364.556 33 11.047 Total 389.072 34 V 0 2 5 Between Groups 40.078 1 40.078 3.693. .063 Within Groups 358.127 33 10.852 Total 398.205 34 V 0 2 6 Between Groups 33.816 1 33.816 2.228 .145 Within Groups 500.939 33 15.180 Total 534.755 34 V 0 2 7 Between Groups 27.028 1 27.028 1.826 .186 Within Groups 488.388 33 14.800 Total 515.415 34 END Between Groups 31.065 1 31.065 .754 .391 Within Groups 1359.266 33 41.190 Total 1390.331 34 73 11 - C % S a 0 2 ANOVA Sum of Squares df Mean Square F Sig. SA_RST Between Groups .579 1 .579 2.742 .107 Within Groups 6.964 33 .211 Total 7.543 34 SA1 Between Groups 59.150 1 59.150 26.648 .000 Within Groups 73.250 33 2.220 Total 132.400 34 SA2 Between Groups 102.857 1 102.857 73.333 .000 Within Groups 46.286 33 1.403 Total 149.143 34 SA3 Between Groups 102.857 1 102.857 76.645 .000 Within Groups 44.286 33 1.342 Total 147.143 34 SA4 Between Groups 65.829 1 65.829 39.395 .000 Within Groups 55.143 33 1.671 Total 120.971 34 SA5 Between Groups 83.314 1 83.314 38.802 .000 Within Groups 70.857 33 2.147 Total 154.171 34 SA6 Between Groups 113.400 1 113.400 36.132 .000 Within Groups 103.571 33 3.139 Total 216.971 34 SA7 Between Groups 97.779 1 97.779 23.908 .000 Within Groups 134.964 33 4.090 Total 232.743 34 END Between Groups 8.750 1 8.750 2.095 .157 Within Groups 137.821 33 4.176 Total 146.571 34 74 11 - D Breathing Frequency ANOVA Sum of Squares df Mean Square F Sig. Breathing Between Groups 5.016 1 5.016 .386 .539 freq. rest Within Groups 428.527 33 12.986 Total 433.543 34 FB1 Between Groups 57.857 1 57.857 1.899 .177 Within Groups 1005.286 33 30.463 Total 1063.143 34 FB2 Between Groups 45.714 1 45.714 2.169 .150 Within Groups 695.429 33 21.074 Total 741.143 34 FB3 Between Groups 99.457 1 99.457 4.076 .052 Within Groups 805.286 33 24.403 Total 904.743 34 FB4 Between Groups 271.607 1 271.607 7.332 .011 Within Groups 1222.393 33 37.042 Total 1494.000 34 FB5 Between Groups 201.600 1 201.600 6.828 .013 Within Groups 974.286 33 29.524 Total 1175.886 34 FB6 Between Groups 348.864 1 348.864 9.195 .005 Within Groups 1252.107 33 37.943 Total 1600.971 34 FB7 Between Groups 497.829 1 497.829 8.789 .006 Within Groups 1869.143 33 56.641 Total 2366.971 34 End Between Groups 113.400 1 113.400 .993 .326 Within Groups 3769.571 33 114.229 Total 3882.971 34 7 5 11 - E Ve /VC0 2 ANOVA Sum of Squares df Mean Square F Sig. VAR00001 Between Groups 60.518 1 60.518" 1.199 .282 Within Groups 1666.023 33 50.486 Total 1726.541 34 VAR00002 Between Groups 31.958 1 31.958 4.741 .037 Within Groups 222.436 33 6.740 Total 254.394 34 VAR00003 Between Groups 38.788 1 38.788 6.781 .014 Within Groups 188.775 33 5.720 Total 227.563 34 VAR00004 Between Groups 11.356 1 11.356 1.558 .221 Within Groups 240.483 33 7.287 Total 251.839 34 VAR00005 Between Groups 11.908 1 11.908 1.699 .201 Within Groups 231.290 33 7.009 Total 243.198 34 VAR00006 Between Groups 29.413 1 29.413 5.941 .020 Within Groups 163.388 33 4.951 Total 192.800 34 VAR00007 Between Groups 40.432 1 40.432 8.262 .007 Within Groups 161.491 33 4.894 Total 201.923 34 VAR00008 Between Groups 41.783 1 41.783 4.855 .035 Within Groups 283.999 33 8.606 Total 325.782 34 END Between Groups 27.289 1 27.289 2.974 .094 Within Groups 302.776 33 9.175 Total 330.065 34 76 Table 12. Pearson product moment correlation of physiological variables measured throughout exercise Fast desaturators Correlations F S a 0 2 F VE F V 0 2 Fast Pearson Correlation 1 -.626 -.852*' S a 0 2 Sig. (2-tailed) .071 .004 N 9 9 9 Fast Pearson Correlation -.626 1 .816*' Ve Sig. (2-tailed) .071 .007 N 9 9 9 Fast Pearson Correlation -.852**^ . 8 1 6 " 1 V 0 2 Sig. (2-tailed) .004 .007 N 9 9 9 • Correlation is significant at the 0.01 level (2-tailed). Slow desaturators Correlations S S a 0 2 S VE ' S V 0 2 Slow Pearson Correlation 1 -.983** -.886*' S a 0 2 Sig. (2-tailed) .000 .001 N 9 : 9 9 Slow Pearson Correlation -.983** 1 .905*' Ve Sig. (2-tailed) .000 .001 N 9 9 9 Slow Pearson Correlation -.886** .905** 1 Vo2 Sig. (2-tailed) .001 .001 N 9 9 9 • Correlation is significant at the 0.01 level (2-tailed). Repeatability measures Table 13. Pearson product moment correlation and Bland Altman test Repeated bouts of maximal exercise and % SaCh response Table 14. Pre and post exercise mean handgrip values One-Sample Statistics Std. Error N Mean Std. Deviation Mean GRIP1 52 34.8462 4.84620 .67205 GRIP2 52 35.0881 4.63702 .64304 One-Sample Test Test Value = 0 95% Confidence Interval of the Mean Difference t df Sig. (2-tailed) Difference Lower Upper GRIP1 51.851 51 .000 . 34.8462 33.4970 36.1953 GRIP2 54.566 51 .000 35.0881 33.7971 36.3790 Table 15. Pre and post exercise MIP and hand grip-values for all subjects Mean Range Pre MIP, cmH 2 0 78.7 ±22.1 28-147 Post MIP, cmH 2 0 77.7 ±20.7 31.7-140.3 Pre Grip, kg 34.8 ±4.8 26-45 Post Grip, kg 35.0 ±4.6 25.5-45 Table 16. Hyperoxic tests independent sample t-test. - repeated measures of % SaC*2 throughout exercise and Tests of Within-Subjects Effects Measure : M E A S U R E _ 1 Type III S u m Source of Squa re s df M e a n S q u a r e F S i g . F A C T O R 1 Spher ic i ty A s s u m e d 109.395 7 15.628 5.861 .000 G r e e n h o u s e - G e i s s e r 109.395 1.951 56 .085 5.861 .022 Huynh-Fe ld t 109.395 5.101 21 .447 5.861 .001 Lower -bound 109.395 1.000 109.395 5.861 .060 F A C T O R 1 * R E S T Spher ic i ty A s s u m e d 43 .622 21 2 .077 .779 .724 G r e e n h o u s e - G e i s s e r 43 .622 5.852 7 .455 .779 .603 Huynh-Fe ld t 43 .622 15.302 2.851 .779 .690 Lower -bound 43 .622 3.000 14.541 .779 .554 E r r o r ( F A C T O R I ) Spher ic i ty A s s u m e d 93 .323 35 2 .666 G r e e n h o u s e - G e i s s e r 93 .323 9.753 9.569 Huynh-Fe ld t 93 .323 25 .503 3.659 Lower -bound 93 .323 5.000 18.665 Tests of Between-Subjects Effects Measure: MEASUREJ Transformed Variable: Average Source Type III Sum of Squares df Mean Square F Sig. Intercept 422398.194 1 422398.194 62250.885 .000 REST 76.017 3 25.339 3.734 .095 Error 33.927 5 6.785 One-Sample Statistics N Mean Std. Deviation Std. Error Mean MINI 9 93.4444 2.24227 .74742 MIN2 9 92.0000 1.87083 .62361 MIN3 9 91.1111 1.45297 .48432 MIN4 9 90.6667 •1.80278 .60093 -MIN5 9 91.3333 2.34521 .78174 MIN6 9 92.4444 2.06828 .68943 MIN7 9 93.2222 2.04803 .68268 END 9 95.0000 1.73205 .57735 One-Sample Test Test Value = 95.56 (rest) Mean 95% Confidence Interval of the Difference t df Sig. (2-tailed) Difference Lower Upper MINI -2.830 8 .022 -2.1156 -3.8391 -.3920 MIN2 -5.709 8 .000 -3.5600 -4.9980 -2.1220 MIN3 -9.186 8 .000 -4.4489 -5.5657 -3.3320 MIN4 -8.143 8 .000 -4.8933 -6.2791 -3.5076 MIN5 -5.407 8 .001 -4.2267 -6.0294 -2.4240 MIN6 -4.519 8 .002 -3.1156 -4.7054 -1.5257 MIN7 -3.424 8 .009 -2.3378 -3.9120 -.7635 END -.970 8 .360 -.5600 -1.8914 .7714 APPENDIX C - INDIVIDUAL DAT A Note that subjects 13 and 53 have been excluded from analyses. Physical characteristics and spirometry data bject # Activity Age Height (m) Weight (kg) FVC FEF 25-75 FEV1 1 Runner 31 1.65 54.00 4.30 4.57 3.81 2 recreat ional 24 1.68 93.90 3.84 4.59 3.53 3 Tri 30 1.80 78.00 4.76 5.69 4.41 4 Tri 25 1.64 59.90 3.73 3.16 3.18 5 Runner /Sk ier 42 1.73 55.90 3.64 3.32 3.00 6 x-count ry Ski 19 1.78 73.90 4.55 4.83 4.10 7 Tr i 31 1.78 61.70 4.17 3.27 3.42 8 Cycl ist 26 1.69 55.80 9 Cycl ist 22 1.66 63.50 4 .25 4.20 3.78 10 Runner 25 1.62 53.10 3.38 2.87 2.78 11 recreat ional 24 1.68 71.70 4.83 5.14 4.35 12 runner 26 1.68 63.50 4.57 3.94 3.81 14 Tr i 30 1.64 63.50 3.24 3.40 2.80 15 Skater 19 1.60 72.60 3.84 3.25 3.24 16 Runner 29 1.68 53.50 17 Runner 24 1.67 62.60 4.25 3.86 3.65 18 x-count ry Ski 27 1.75 67.10 4.45 3.65 3.80 19 x-count ry Ski 22 1.80 67.60 4.54 3.33 3.71 20 Runner 25 1.71 59.40 4.47 4.96 3.99 21 field h o c k e y 22 1.72 70.80 4.05 3.62 3.45 22 Tr i 30 1.69 54.90 4.20 4 .55 3.75 23 recreat ional 19 1.60 . 62.10 4.00 3.92 3.48 24 Tri 25 1.68 59.00 4.13 4.13 3.63 25 Tri 19 1.71 52.60 3.04 4 .62 3.00 26 Tr i 24 1.69 61,70 3.22 4 .23 3.00 27 S w i m m e r 29 1.79 77.10 4.79 5.67 4.48 28 Runner 31 1.75 67.60 4.09 4.19 3.61 29 Runner 27 ' 1.76 53.10 4.54 3.56 4.06 30 Tr i 30 1.81 61.20 4.46 2.93 3.42 31 S w i m m e r 27 1.72 74.40 3.89 3.60 3.40 32 recreat ional 26 1.63 54.90 4.14 4.70 3.73 33 recreat ional 34 1.63 71.00 5.08 3.34 3.87 34 runner 35 1.55 45 .00 3.48 4.49 3.12 35 Tri 20 1.59 45 .40 3.67 3.46 3.22 36 recreat ional 22 1.66 63.00 3.80 2.79 3.07 37 recreat ional 24 1.71 54.40 3.74 3.98 3.42 38 runner 25 1.73 64.00 4.66 3.83 3.83 39 recreat ional 20 L 6 7 65.80 4.39 4.30 3.76 40 recreat ional 19 1.70 56.70 3.73 4.49 3.50 41 soccer 22 1.78 64.40 5.16 3,72 4.07 42 Tri 31 1.71 59.00 3.63 2.98 3.02 43 Tri 34 1.54 47.60 3.19 2.61 2.69 82 44 Tri 24 1.66 56.70 3.76 3.55 3.26 45 Skier 25 1.75 76.70 4.69 3.45 3.74 46 Tri 31 . 1.68 50.80 4.15 4.07 3.61 47 Tri 35 1.60 59.00 3.20 3.81 2.89 48 Tri 26 1.82 67.00 4.47 3.63 3.80 49 Tri 30 1.76 65.80 4.79 6.06 4.61 50 Tri 24 1.55 53.50 3.65 3.38 3.15 51 Recreat ional 21 1.71 62.10 3.91 4.76 3.64 52 Recreat ional 30 1.69 52.60 3.98 4.05 3.49 54 Tr i 34 1.67 57.60 3.79 3.10 3.08 M V V and pre / post exercise MLP and hand grip measures. Subject 12 sec. Pre-Grip Post-Grip Pre-MIP Post-MIP # MW (l/min) (kg) (kg) (cmH20) (cmH20) 1 188.60 32.00 31.25 89.08 88.29 2 213.20 32.00 32.00 95.12 102.59 3 213 .80 43 .00 40.00 90 .88 68.34 4 139.20 34.00 35.83 77.68 88.01 5 141.10 41 .50 38.00 68 .09 56.20 6 189.90 35.00 37.00 88 .57 .80.51 7 174.60 34.00 35.00 75.50 87.05 8 36.00 36.00 66.68 65.58 9 129.40 35.00 35.00 96.21 89.80 10 117.90 28.50 29.50 81 .33 67.73 11 154.60 30.50 31.00 137.08 112.07 12 , 167.10 36.50 37.00 88 .84 86.63 14 123.10 35.50 38.00 67.17 75.27 15 122.00 35.50 34.00 86.76 62.39 16 27.00 29.00 64 .04 82.50 17 164.10 38.00 38.00 117.26 111.21 18 189.30 37.00 38.50 147.06 140.34 19 143.40 33.00 35.50 81 .14 80.70 20 193.00 37.50 35.50 75.52 67.63 21 154.90 34.00 35.00 113.35 102.86 22 151.00 37.00 39.00 87.50 97 .46 23 133.70 39.00 40.00 77.54 89.25 24 131.80 27.50 25.50 72.17 78.26 25 132.40 32.00 . 30.50 61.42 67^87 26 125.90 39.00 38.00 79.34 76.76 27 188.10 38.50 40.50 92.82 97.94 28 122.80 38.50 38.00 71.88 68 .34 29 121.70 38.50 37.00 55.97 59.03 30 123.90 39.50 36.00 88 .49 67.89 31 137.40 44 .50 43 .50 71.78 78.13 32 168.50 31.00 31.00 95.71 88.98 33 142.80 40.00 41.50 81 .19 82.21 34 113.00 30.00 30.00 28.41 33.61 35 130.40 30.00 32.50 65 .82 59.60 36 113.20 36.00 36.00 76.93 91.52 37 102.00 27.50 29.00 41 .23 41.83 38 136.30 43 .00 42.00 58.99 61.95 39 155.70 39.00 38.00 45 .45 40 .66 40 134.60 26.00 27.50 1 29.68 31.75 41 154.00 . 37.50 37.00 79.67 77.38 42 152.60 36.50 37.00 99 .96 94.03 43 121.20 26.50 26.00 59.67 57.18 44 121.10 27.00 26.00 74.23 72.18 45 156.40 36.50 37.00 71 .24 56.49 46 . 159.30 30.00 29.00 71 .65 75.72 47 127.90 33.50 34.00 60 .34 60.02 ' 48 147.40 35.50 37.50 61 .99 68.62 49 189.30 45.00 45.00 112.95 111.90 50 114.60 . 26 .00 28.00 89 .25 95.07 51 182.90 37.00 40.00 83 .85 98.01 52 142.10 34.00 34.00 73 .43 72.18 54 148.50 35.00 37.50 68 .67 76.43 Physiological variables measured during rest and exercise. Subject # V02tnax % predicted Resting HR Max Rest EndSa02% (ml/kg/min) Of VO2HKIX HR Sa02 % 1 53.15 96.64 66 184 97 97 2 28.07 93.15 86 177 97 98 3 47.67 94.27 63 179 98 88 4 54.15 100.23 60 187 98 88 5 48.47 83.24 54 183 97 94 6 40.87 83.70 59 189 98 92 7 51.63 97.11 49 186 98 90 8 49.18 99.49 68 196 98 93 9 46.33 94.22 54 170 98 95 10 45.28 81.60 60 180 98 95 11 46.20 97.87 68 192 99 91 12 46.28 91.04 66 195 98 92 14 40.60 76.48 65 172 97 90 15 44.58 95.85 69 176 97 90 16 49.58 88.87 56 166 97 90 17 52.50 100.11 58 181 97 93 18 54.35 102.85 60 193 99 90 19 45.55 83.80 63 186 98 89 20 52.65 94.99 61 180 98 94 21 42.18 80.00 50 185 98 93" 22 44.93 89.16 62 191 99 95 23 36.65 78.62 81 193 97 96 24 52.83 97.13 53 174 97 94 25 47.35 83.70 58 181 98 91 26 47.78 99.78 69 193 99 91 27 43.45 93.12 50 161 96 95 28 34.43 72.43 . 79 178 97 94 29 52.85 93.78 74 187 97 94 30 48.68 89.35 75 190 98 95 31 42.85 87.38 47 191 97 91 32 35.13 73.59' 75 180 98 90 33 41.63 94.50 60 176 99 94 34 46.95 81.70 59 157 99 92 35 54.98 110.34 57 185 98 96 36 42.98 90.29 59 179 98 96 37 44.18 86.65 67 189 98 90 38 42.23 87.89 61 181 99 94 39 38.68 90.70 78 184 98 91 40 36.98 72.58 60 182 99 87 41 48.95 87.09 64 184 97 95 42 53.70 108.11 48 160 99 94 43 51.80 96.82 50 171 98 95 44 48.15 89.53 70 171 98 98 45 47.53 99.97 51 163 98 95 86 46 45 .98 82.52 78 192 95 95 47 40 .20 76.25 58 161 98 94 48 47 .70 89.46 57 196 98 95 49 48 .38 103.58. , 68 199 98 95 50 61.38 131.72 60 183 98 92 51 40 .13 75.30 83 177 96 89 52 44 .25 89.35 69 171 98 90 54 48 .63 91.64 64 186 98 . 94 End tidal C O 2 values from rest to peak exercise. Subject Rest # ETCO2 SOW 100W 150W 200W 250W 300W 1 9 37.92 38.65 39.77 37.87 35 .73 c. 3 38.81 43 .54 43 .78 43 .74 46.81 43 .99 36.45 4 37.73 45 .90 49 .76 49.85 49 .44 47 .45 42 .74 5 32 .55 29 .29 29.33 36.47 31.45 6 34.11 37 .05 37.81 37.35 36.39 32 .48 7 36.74 39 .95 44.67 46.46 47.41 45 .53 42 .85 8 33.09 37.80 40.21 40.32 40 .35 44 .65 9 35.90 42 .25 44 .44 46 .37 45 .49 39 .45 10 33.99 36.39 34.30 34.36 33.60 31.70 11 37.56 36.58 37.00 39.72 41 .70 42 .38 39.68 12 36 .54 34.32 41.41 43.12 41 .29 39 .65 36.67 14 35 .05 36.60 37.23 36.85 33.85 15 31.40 38.62 40.31 42.24 42 .43 44 .03 16 40 .37 43 .25 45 .10 43 .86 39.52 36.51 17 32.22 38.41 40 .03 41 .25 41 .12 39 .95 38.98 18 35.40 34.79 37.37 37.33 39.04 38.30 35.19 19 34.33 37.83 42.46 43.20 45 .90 46 .62 42 .62 20 37.09 39.76 42 .65 42.89 42.11 41 .49 37.34 21 37 .53 38 .24 38.94 41.21 39.46 37.60 22 26 .43 38 .68 38.05 38.66 38.68 31.81 23 37.00 35.36 41.51 40.83 36.60 24 34 .05 38 .75 40.34 42.07 , 43 .23 41 .86 37.94 25 38.22 38 .95 40.81 40 .18 37.86 26 39.17 42 .26 43 .96 43 .93 43 .56 40 .97 27 35.33 39.03 39.46 41.44 42 .08 42 .70 39.49 28 32.32 35.66 34.16 33.63 32.34 29 34.67 40 .60 44.96 49.42 49 .49 46.11 30 34 .60 37.62 40 .45 41.94 44 .63 • 43 .39 41 .38 31 43 .29 41 .76 43.32 43.34 42 .57 37 .84 37.20 32 32.70 38.47 37.28 31.12 29.00 33 36.22 36.29 37.86 37.04 35.26 30.02 34 38 .05 35.79 34.96 33.19 35 35.11 39.21 41.58 41.21 38.37 36 37 .15 37.60 40.50 41.03 39.67 34 .83 37 27 .96 36.37 37.46 34.03 34.39 38 27 .87 34.76 38.18 • 41.10 41.83 39 35.14 35.83 36.94 37.65 35.54 40 34 .25 31 .55 34.61 36.73 37.35 41 35 .89 36.01 37.16 38.97 39.96 35.08 34.02 42 35.57 37.04 39.93 40 .45 35.87 31 .30 43 29 .26 37.04 36.90 36.30 34.40 44 33.39 35.00 34.17 34.89 31.14 45 33.94 35.76 38.03 39.00 38.32 38.82 37.90 46 35.13 . 34.24 35.76 36.55 36 .49 33 .67 47 41 .13 35.18 36.98 38.34 35.92 48 30.80 34 .26 35.48 35.89 36.99 37.37 49 30.12 34.53 36.28 37.43 37.20 ' 37.41 50 42 .73 37.51 39.83 39.14 40 .26 40 .52 51 31.24 37.75 39.50 37.44 36.52 35 .24 52 36 .05 39.43 38.79 39.55 36.73 54 35.09 34 .88 39.58 40.88 40.67 36.37 Ventilation values at rest and during exercise. Subject # Resting V E V 0 2 m a x V E 1 5.94 82.29 2 13.39 85.29 3 4.21 129.41 4 10.06 94.90 5 4.60 102.07 6 6.44 108.85 7 9.80 88.64 8 8.17 76.99 9 8.66 91.63 10 6.77 77.71 11 8.34 87.42 12 7.44 85.22 14 7.21 81.04 15 7.40 79.11 16 4.80 79.63 17 . 7.42 93.43 18 7.34 120.46 19 8.78 76.31 20 7.02 101.01 21 6.71 90.24 22 8.91 87.23 23 5.86 54.00 24 9.42 83.19 25 8.06 75.40 26 9.27 82.10 27 7.45 89.69 28 11.47 65.36 29 6.97 67.62 30 6.35 80.81 31 7.35 92.86 32 6.76 86.87 33 9.50 94.45 34 9.57 66.04 35 7.33 72.92 36 7.06 81.98 37 7.25 74.79 38 8.31 66.89 39 6.24 79.29 40 12.12 47.80 4 1 . 6.89 88.56 42 10.68 114.69 43 8.49 69.20 44 8.80 83.06 45 9.24 85.75 46 9.37 82.46 47 8.47 66.66 48 10.28 81.38 49 10.57 90.81 50 10.09 87.28 51 8.78 66.92 52 7.79 67.66 54 6.90 73.48 A P P E N D I X D - Q U E S T I O N N A I R E S Name: Age: ; Code:_ Date/Time PAR-Q YES NO 1 .Has a doctor ever said you have a heart condition and recommended only medically supervised physical activity? 2.Do you have chest pain brought on by physical activity? 3.Have you developed chest pain in the past month? 4. Do you tend to lose consciousness or fall over as a result of dizziness? 5. Do you have a bone or joint problem that could be aggravated by the proposed physical activity? 6. Has a doctor ever recommended medication for your blood pressure or a heart condition? 7. Are you aware through your own experience, or a doctor's advice, of any other physical reason against your exercising without medical supervision? 8. Are you pregnant? Are you currently taking any medications? Including the Pill? Please List: Do you have asthma, other lung problems or significant illness? Please List: 92 Do you currently smoke? YES / NO Are you a past smoker? YES / NO Do you do an hour or more of vigorous exercise per week? If yes, please indicate the type of activity, average frequency and duration: How many months over the past year have you exercised a similar amount? How many years have you exercised a similar amount? Menstrual History 1. Are you having regular periods? YES / NO 2 . How long is your cycle length? (days) 3. How many days long is your flow? (days) 4 . Can you usually tell, by the way you feel, that your period is coming? YES / NO 5. Do you usually experience the following symptoms ? Breast tenderness YES / NO Appetite changes YES / NO Mood Changes YES/NO Fluid retention YES / NO 6. How many times did you menstruate in the past year? 7. How many periods have you missed in the last five years? 93 8. Are you currently taking oral contraceptives? YES / NO If yes, for how long? ; 8. What is the name of the oral contraceptive pill which you are taking? . 9. When was the last start of your period? (DAY 1) VChmax prediction equation (George et al., Med Sci Sports and Exerc 29(3):415-423, 1997) Perceived functional ability (PFA) Suppose you were going to exercise continuously on an indoor track for 1 mile. Which exercise pace is just right for you? Circle the appropriate number: 1 Walking at a slow pace (18mins per mile or more) 2 ' • 3 Walking at a medium pace (16 mins per mile 4 5 Walking at a fast pace (14 mins per mile) 6 7 Jogging at a slow pace (12 mins per mile) 8 9 Jogging at a medium pace (10 mins per mile) 10 II Jogging at a fast pace (8 mins per mile) 12 13 Running at a fast pace (7 mins per mile) How fast could you cover a distance of 3 miles and NOT become breathless or overly fatigued? Be realistic. Circle the appropriate number 1 I could walk the entire distance at a slow pace (18mins per mile or more) 2 3 I could walk the entire distance at a medium pace (16 mins per mile) 4 5 I could walk the entire distance at a fast pace (14 mins per mile) 6 7 I could jog the entire distance at a slow pace (12 mins per mile) 8 9 I could jog the entire distance at a medium pace ( 10 mins per mile) 10 I I I could jog the entire distace at a fast pace (8 mins per mile) 12 13 I could run the entire distance at a fast pace (7 mins per mile) 95 Physical activity rating (PA-R) Select the number that best describes your overall level of physical activity for the previous 6 months: 0 = avoid walking or exertion; e.g. always use the elevator and drive instead of walking 1 = light activity: walk for pleasure, routinely use stairs, occasionally exercise sufficiently to cause heavy breathing 2 = moderate activity: 10 to 60 minutes per week of moderate activity; such as golf, aerobics, tennis, bowling, weight lifting, yard work, walking. 3 = moderate activity: over 1 hour per week of moderate activity as described above 4 = vigorous activity; run less than one mile per week or spend less than 30 minutes in comparable activity such as running or jogging, swimming, cycling, rowing, aerobics, soccer, basketball, tennis, racquetball, squash. 5 = vigorous activity: run one mile to less than 5 miles per week or spiend 30 mins to less than 60 minutes per week in comparable activity. 6 = vigorous activity: run 5 miles to less than 10 miles per week or spend one hour to less than 3 hours per week in comparable activity. 7 = vigorous activity: run 10 miles to less than 15 miles per week or spend 3 hours to less than 6 hours per week in comparable activity. 8 = vigorous activity: run 15 miles to less than 20 miles per week or spend 6 hours to less than 7 hours per week in comparable activity. 9 = vigorous activity: run 20 to 25 miles per week or spend 7 to 8 hours per wekk in comparable physical activity. 10= vigorous activity: run over 25 miles per week or spend of 8 hours per week in comparable activity. V0 2 max (ml/kg/min) prediction equation = 45.513 + (6.564 * gender) - (0.749 * BMI) + (0.724 * PFA) + (0.788 * PA-R) Gender (0 = females, and 1 = males) R = 0.86, SEE = 3.44 ml/kg/min 96 

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