Influence of Exercise Modality on Body Composition, Insulin Resistance and Functional Fitness in Aging: A Randomized Controlled Trial
Davidson, Lance Eric
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Excessive abdominal obesity, coupled with a decline in muscle mass and physical function that is exacerbated by sedentary living, contributes substantively to the disease and disability common to our aging population. The Senior Study, a randomized controlled trial designed to investigate the health benefits associated with performing resistance exercise (RE), aerobic exercise (AE), or a combination of both exercise modalities (RAE) for six months in the absence of caloric restriction, was conducted on otherwise healthy but abdominally obese, sedentary men (n=57) and women (n=79) between the ages of 60 and 80. The purpose of the first manuscript (Chapter 3) was to compare the effects of exercise modality on visceral obesity and insulin resistance in the Senior Study. All exercise groups significantly reduced total abdominal and visceral fat (P<0.05) and waist circumference (P<0.001), which measure explained 30% of the variance in total abdominal fat changes (P<0.001). AE and RAE improved insulin sensitivity (P<0.05), but the RE group did not (P>0.1). The greatest insulin sensitivity increase was observed within the RAE group (48% increase, P<0.001). The purpose of the second manuscript (Chapter 4) was to evaluate the effects of exercise modality on cardiorespiratory and functional fitness in the Senior Study. AE and RAE increased cardiorespiratory fitness (P<0.001), whereas RE did not (P>0.1). All exercise groups improved functional fitness performance (P<0.001), but age- and sex-specific percentile ranking improvement within RAE was greater than AE (P<0.01). RE and RAE significantly increased skeletal muscle (P<0.01), predominantly in the upper body, while AE did not (P=1.0). AE and RAE reduced total fat (P<0.001). Both fat loss and muscle gain were independent predictors of improvements in functional fitness (P<0.05). The findings from these studies demonstrate conclusively that a combined resistance and aerobic exercise program without caloric restriction is an optimal strategy for the therapeutic reduction of health risk in abdominally obese men and women. While each exercise modality offers distinct benefits and remains a viable option for needs-based exercise prescription, the combination was associated with the greater simultaneous improvements to body composition, insulin resistance, and cardiorespiratory and functional fitness than either resistance or aerobic exercise alone.