The Effect of Exercise Training on Physical Fitness in Type 2 Diabetes Mellitus

Abstract

Several studies have examined the effects of aerobic exercise training and resistance exercise training on physical fitness. Few studies, however, have compared changes in cardiorespiratory fitness between aerobic training only or in combination with resistance training. Additionally, no study to date has compared strength gains between resistance training and combined exercise training in type 2 diabetes mellitus (T2DM). PURPOSE: We evaluated the effects of aerobic exercise training (A), resistance exercise training (R), combined aerobic and resistance training (A+R) and a sedentary control group (C) on cardiorespiratory fitness and muscular strength in individuals with T2DM. METHODS: 251 participants in the Diabetes Aerobic and Resistance Exercise (DARE) trial were randomly allocated to A, R, A+R or C. Peak oxygen consumption (VO2peak), maximal workload and treadmill time were determined following maximal exercise testing at 0 and 6 months. Muscular strength was measured as the 8 RM on the leg press, bench press and seated row. Responses were compared between younger (39-54) and older (55-70) adults and between sexes. RESULTS: VO2peak improved by 1.73 and 1.93 mLO2/kg/min with A and A+R respectively compared to C (p<0.05). This was paralleled by improvements in workload (23.6 and 19.8 W for A and A+R respectively) as well as significant changes in treadmill time (1.2 and 1.1 min for A and A+R respectively) (p<0.05). Strength improvements were observed after A but gains were greater following A+R and R on the leg press (A+R:48%, R:65%) bench press (A+R:38%, R:57%) and seated row (A+R:33%, R:41%)(p<0.05). There was no main effect of age or sex on training performance outcomes. There was however a tendency for older participants to increase VO2peak more with A+R (+1.5 mLO2/kg/min) than with A only (+0.7 mLO2/kg/min) whereas improvements among younger participants were similar between A+R (+1.71 mLO2/kg/min) and A (+1.91 mLO2/kg/min). CONCLUSION: Aerobic training improved cardiorespiratory fitness and resistance training improved strength. Combined training did not provide any additional benefits nor did it mitigate improvements in fitness in younger subjects. In older subjects, there was a trend to greater aerobic fitness gains with combined training versus aerobic training alone. Funding support: Canadian Institutes of Health Research, Canadian Diabetes Association.