Exercise and glucose metabolism in older women: the roles of volume and intensity

 

Loretta DiPietro

Department of Exercise Science, The George Washington University School of Public Health and Health Services, Washington, DC, USA

 

We studied healthy, older (65-88 y) women over a 36-week training period to determine: 1) the effect of abdominal obesity on simultaneous measures of insulin resistance at the level of adipose tissue, liver, and skeletal muscle; 2) the effects of exercise intensity on multi-tissue insulin resistance; and 3) progressive improvements in glucose tolerance with exercise of different type and intensity. Subjects (N=25) were randomized to either a higher- (AT_H; 80% VO_2peak) or moderate-(AT_M; 65% VO_2peak) intensity aerobic training or a lower-intensity resistance training (RT_L) group. Subjects exercised under supervision on 4 days/week for 45-65 min. Abdominal obesity was defined as an abdominal circumference >97.5 cm. Peripheral, adipose tissue, and hepatic insulin sensitivity were determined 72-h after the last bout of exercise using in vivo methodology. Glucose tolerance was determined 48-h following exercise using the OGTT.  At baseline, we found evidence that dysregulated fatty acid reesterification with abdominal obesity serves as a pathophysiological link to perturbed glucose metabolism across multiple systems. After 36-weeks of training, we observed a greater short-term (i.e., 48-h) effectiveness of RT_L (p<0.05) compared with both AT_H and AT_M on improvements in glucose tolerance due, in part, to higher circulating levels of FFA after a large volume of aerobic exercise. In contrast, after 72 hours we observed improved peripheral glucose utilization (p<0.02) and glycerol turnover (p<0.05) with training that was statistically significant only in the AT_H compared with the AT_M and RT_L groups. These training-related improvements in insulin sensitivity and glucose tolerance were independent of changes in body composition and VO_2peak. We conclude that whereas higher-intensity aerobic exercise has more enduring benefits toward insulin action, the metabolic benefit-to-stress ratio of lower-intensity resistance exercise may be higher. These benefits may also decay more quickly, however, thus requiring lower-intensity exercise to be performed more frequently in order to result in improved metabolic function.

 

Key words: Aging, Diabetes, Exercise, Metabolism