Effects of aerobic and resistive exercise training on glucose disposal and skeletal muscle metabolism in older men

Abstract

Background: Aging is associated with insulin resistance, primarily as a result of physical inactivity and increased abdominal obesity. We hypothesized that aerobic (AEX) or resistive (RT) exercise training would result in comparable improvements in glucose disposal in older men, but that there would be different metabolic adaptations in skeletal muscle.

Methods: Thirty-nine older (63+/-1 years, mean+/-standard error of the mean), overweight and obese (body mass index=30.3+/-0.4 kg/m2) men were assigned to AEX (treadmill walking and/or jogging, n=19) or RT (upper and lower body, n=20) programs 3 d/wk for 6 months, with 9 completing AEX and 13 completing RT. Testing before and after the exercise programs included body composition, euglycemic-hyperinsulinemic clamps, and vastus lateralis muscle biopsies.

Results: Maximal oxygen consumption (VO2max) increased by 16% after AEX (p<.01), while leg and arm muscle strength increased by 45+/-5% and 27+/-5% after RT (p<.0001). Although participants were monitored to maintain their body weight during the exercise program, body weight decreased by 2% after AEX (p<.05), and increased by 2% after RT (p<.05). Whole-body glucose disposal, determined during the last 30 minutes of a 2-hour 480 pmol/m2/min euglycemic-hyperinsulinemic clamp, increased comparably by 20%-25% after AEX (51+/-5 to 61+/-5 microM/kgfat-free mass/min, p<.05) and RT (49+/-3 to 58+/-3 microM/kgfat-free mass/min, p<.05). The increase in vastus lateralis muscle glycogen synthase fractional activity in response to insulin stimulation was significantly higher after AEX compared to after RT (279+/-59% compared to 100+/-28% change, p<.05). Neither AEX nor RT altered muscle glycogen synthase total activity, glycogen content, or levels of phosphotidylinositol 3-kinase.

Conclusion: These results suggest that AEX and RT result in comparable improvements in glucose metabolism in older men, whereas an increase in insulin activation of glycogen synthase occurred only with AEX. These improvements in insulin sensitivity could reduce the risk of metabolic syndrome and type 2 diabetes and attenuate the development of cardiovascular disease.