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The effects of resistance training during early cardiac rehabilitation (phase II) on strength and body composition

University of British Columbia

The effects of combined resistance training (RT)and aerobic exercise were compared to aerobic only (AO) exercise on measures of strength, fat mass (FM), lean mass (LM), and muscle mass (MM). Twenty-seven haemodynamically stable male cardiac patients (age range 39-66 years) performed 3 weeks (6 sessions) of aerobic exercise 2x/week before being randomly assigned to one of three groups: aerobic only (AO; n = 10) early-start resistance training (ESRT; n = 8) and late-start resistance training (LSRT; n =9). All three groups participated in 16 weeks (32 sessions) of aerobic exercise, however, the ESRT and LSRT groups performed 12 and 6 weeks (24 or 12 sessions respectively) of moderate-high intensity (70-79% of 1RM) weight training (7 exercises). There were no haemodynamic complications due to the RT over the course of the study. Body composition was measured using anthropometric girths, sum of skinfolds (SOS), body weight (BW), waist-to-hip ratio (WHR), Near Infrared Photospectometry (NIR) and Dual- Energy X-ray Absorptiometry (DXA), DXA measures were only done for 14 subjects (AO & LSRT, n=4; ESRT, n=6) and due to the small group numbers results were used as supplemental information. MM was calculated from a regression equation based on skinfold-corrected limb girths. Results: A 3 (Group) X 4 (Time) ANOVA with repeated measures on the last factor, indicated no significant changes for the group effect in BW (p=0.6) and SOS (P=0.9), DXA & NIR L M (both p=0.6); DXA & NIR FM (p=0.4 & p=0.9, respectively) or M M (p=0.2), or individual girths. However, a significant difference occurred for the time factor for WHR (F[sub 3,72]= 5.4, p<.002) and for waist girths (F[sub 3,72]= 4.02, p<.01) with no changes to hip girths (p=0.7) or umbilicus skinfolds (p=0.9)suggesting a decrease in subjects' visceral fat. The group X time factor showed significance for the DXA LM (F[sub 2,11]= 5.7; p<.02), and MM (F[sub 6,72]= 5.1, p<.001) indicating that changes in response to the RT interventions over time were dissimilar between the groups at specific assessment periods. The AO group lost 2 ± 1.5% DXA LM[sub pre-to-post] and 3.3 ± 2.1% MM while the ESRT and LSRT groups gained DXA LM[sub ESRT] 3.9% ±1% and MM [sub ESRT] 4.0 ± 1.4% MM and DXA LM[sub LSRT] .8 ± 1.1% and MM[sub LSRT] 4.0± 1.4%. Overall pre-to post-training strength changes were significantly different (F[sub 2,22]= 9.5, p<.001) between groups with the greatest changes occurring in the ESRT group (27± 4.2%) followed by the LSRT group (25 ± 3.3%) and then the AO group (7.3 ± 2.6%). A post-hoc Tukey HSD analysis revealed the significant difference to be between the RT and AO groups (p<.05); no significant difference existed between the two RT groups (p=.35). Upper and lower body pre-to post training strength changes were significantly different (F[sub 2,22] = 5.8, p<.009 and F2,22 = 7.4, p<.004, respectively) with the upper body increasing 6.5%[sub AO], 17.9% [sub ESRT], 18.4% [sub LSRT] and lower body increasing 7.5% AO, 39.0% [sub ESRT], 33.8% [sub LSRT]. Conclusions: RT significantly increased strength with the greatest gains occurring in subjects who started RT earlier rather than later in the cardiac rehabilitation program (CRP). However, there were no significant strength differences between the ESRT and the LSRT groups suggesting that RT can begin as late as 10 weeks after starting a CRP and show similar strength gains to those who start RT earlier. There were no significant changes in body composition between groups, however, the AO group showed a numerical loss in MM and DXA LM while the RT groups showed a numerical increase in these variables. A statistically significant group X time interaction effect for MM (p<001) and DXA LM ((p<.02) suggests that RT maintains or increases MM and DXA LM, while AO exercise actually caused losses in these variables. WHR for all groups significantly decreased over time regardless of training intervention suggesting that RT may not play a primary function on WHR changes. WHR changes were due to a loss in waist girths suggesting a loss in visceral fat. The primary goal of a CRP is to return the patient to a normal life as quickly as possible, RT can play a vital role in this process. RT can begin as early as 4 weeks post-cardiac event with minimal risk of haemodynamic complications in selected low-moderate risk cardiac patients. RT has many physiological benefits and by incorporating it earlier in a CRP, cardiac patients have an opportunity to incur these benefits sooner. This may then facilitate a quicker return to work and leisure activities.

Thesis/Dissertation

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2009-05-05

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http://hdl.handle.net/2429/7879

Human Kinetics

University of British Columbia

UBCV

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