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Effect of Exercise Training on Physical Fitness in Type 2 Diabetes

Combined training does not provide additional benefits or show improvements in fitness in younger subjects compared with aerobic and resistance training alone. In older subjects, there was a trend to greater aerobic fitness gains with aerobic + resistance versus aerobic alone….

Few studies have compared changes in cardiorespiratory fitness between aerobic training only or in combination with resistance training. In addition, no study to date has compared strength gains between resistance training and combined exercise training in Type 2 diabetes (T2DM).

The study evaluated the effects of aerobic exercise training (A group), resistance exercise training (R group), combined aerobic and resistance training (A + R group), and sedentary lifestyle (C group) on cardiorespiratory fitness and muscular strength in individuals with T2DM.

Two hundred and fifty-one participants in the Diabetes Aerobic and Resistance Exercise trial were randomly allocated to A, R, A + R, or C. Peak oxygen consumption (V·O2peak), workload, and treadmill time were determined after maximal exercise testing at 0 and 6 months. Muscular strength was measured as the eight-repetition maximum on the leg press, bench press, and seated row. Responses were compared between younger (aged 39–54 yr) and older (aged 55–70 yr) adults and between sexes.

Results: V·O2peak improved by 1.73 and 1.93 mL O2·kg−1·min−1 with A, and A + R, respectively, compared with C (P < 0.05). Strength improvements were significant after 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 V·O2peak more with A + R (+1.5 mL O2·kg−1·min−1) than with A only (+0.7 mL O2·kg−1·min−1).

The prevalence of T2DM typically increases with age, and aging is usually associated with progressive decrements in various components of physical work capacity and notable declines in cardiorespiratory fitness and muscle strength. Moreover, exercise capacity has been shown to be reduced in people with T2DM compared with age-, body mass-, and activity-matched controls even in the absence of diabetic complications. Low cardiorespiratory fitness and decrements in bone density and skeletal muscle strength are strong predictors of disability among older individuals. A  combined exercise program seems to generate greater reductions in HbA1c value than either aerobic or resistance training alone. It remains unclear, nonetheless, whether combined exercise training would provide similar gains in both cardiorespiratory fitness and strength compared with either mode of training alone in individuals with T2DM. On the one hand, increased fatigue might have a negative impact on workout intensity compared with doing just one kind of exercise. Conversely, older individuals often have sarcopenia, and strength training might be helpful in permitting them to maximize their aerobic workouts.

In the present study, we report the effects of aerobic exercise training, resistance exercise training, and the combination of aerobic and resistance exercise training on cardiorespiratory fitness and muscular strength in the Diabetes Aerobic and Resistance Exercise (DARE) trial. An additional purpose of this investigation was to examine if fitness exercise responses in the training groups were affected by age and sex. We hypothesized that changes in cardiorespiratory fitness and strength would be similar in the aerobic exercise training and resistance exercise training groups, respectively, compared with the combined aerobic and resistance training group. We also hypothesized that younger and older adults as well as men and women would respond similarly to exercise training.

In summary, combined exercise training did not seem to provide additional benefits nor did it mitigate changes in physical fitness in younger participants compared with the effects of aerobic training alone on aerobic fitness or resistance training alone on muscular fitness. In older subjects, there was a trend to greater aerobic fitness gains with combined training versus aerobic training alone. These findings provide further evidence supporting the additional health benefits of combined aerobic and resistance exercise training especially for older people with T2DM.

Medicine and Science in Sports and Exercise®. 2010;42(8):1439-1447