Exercise and improved insulin sensitivity in older women: evidence of the enduring benefits of higher intensity training

Few studies have compared the relative benefits of moderate- vs. higher intensity exercise training on improving insulin sensitivity in older people while holding exercise volume constant. Healthy older ( 73 +/- 10 yr) women ( N = 25) who were inactive, but not obese, were randomized into one of three training programs ( 9-mo duration): 1) high- intensity [ 80% peak aerobic capacity ( V-O2 peak); TH] aerobic training; 2) moderate- intensity ( 65% V-O2 peak; T-M) aerobic training; or 3) low-intensity ( stretching) placebo control (50% V-O2 peak; C-TB). Importantly, exercise volume ( 300 kcal/session) was held constant for subjects in both the T-H and the T-M groups. V-O2 peak was determined by using a graded exercise challenge on a treadmill. Total body fat and lean mass were determined with dual-energy X-ray absorptiometry. The rate of insulin-stimulated glucose utilization as well as the suppression of lipolysis were determined similar to 72 h after the final exercise bout by using a two-step euglycemic-hyperinsulinemic clamp. We observed improved glucose utilization at the higher insulin dose with training, but these improvements were statistically significant only in the T-H (21%; P = 0.02) compared with the T-M ( 16%; P = 0.17) and C-TB ( 8%; P = 0.37) groups and were observed without changes in either body composition or V-O2 peak. Likewise in the T-H group, we detected a significant improvement in insulin-stimulated suppression (%) of adipose tissue lipolysis at the low-insulin dose ( 38-55%, P < 0.05). Our findings suggest that long-term higher intensity exercise training provides more enduring benefits to insulin action compared with moderate- or low-intensity exercise, likely due to greater transient effects.