Diabetes Epidemiology and Management (Oct 2021)
Transient effect of aerobic exercise training on insulin sensitivity
Abstract
Background: Aerobic exercise training has well established effects on increasing insulin sensitivity. However, the extent to which exercise in the absence of weight loss and/or negative energy balance results in sustained elevation in insulin sensitivity is unclear. Objective: This study aimed to assess the effects of long-term aerobic exercise training on insulin sensitivity in healthy premenopausal women while controlling for energy balance. Design: Female participants ages 20–40 (Mean BMI=27.0) trained three times per week throughout the study on a cycle ergometer under supervision of an exercise physiologist. Participants completed a pre-training evaluation and three post-training evaluations at times ranging from 8 to 20 weeks post-baseline, including insulin sensitivity and peak VO2 testing. Before each evaluation, participants stayed overnight in a room calorimeter for 23 h and food intake was adjusted to maintain energy balance. A cycle ergometer graded exercise test was completed after warm-up to determine peak oxygen uptake (VO2peak). Hyperinsulinemic-euglycemic clamp measures were conducted to determine insulin sensitivity. Adjusted and unadjusted models were performed for log insulin sensitivity and peak VO2 using linear model for repeated measures. Results: Data from 31 participants with complete data were analyzed. The models determined that mean VO2peak (F = 5.56 (3,89) p = 0.0015) and mean insulin sensitivity (F = 3.92 (3,65) p = 0.0123) differed among timepoints. Exercise training elicited an increase in VO2peak from pre-training (25.5 ± 1.15) to all three post-training evaluations (26.7 ± 1.15 vs. 27.4 ± 1.07 vs. 27.2 ± 1.17, respectively). In contrast, insulin sensitivity increased from pre-training to first post-training evaluation, but then returned to levels not different from baseline at the subsequent two evaluations. Conclusions: Improvement in insulin sensitivity resulting from exercise training appears to be transient and returns to baseline with continued training.
