Effect of mild exercise training on glucose effectiveness in healthy men

OBJECTIVE - To detect whether mild exercise training improves glucose effectiveness (S-G), which is the ability of hyperglycemia to promote glucose disposal at basal insulin, in healthy men. RESEARCH DESIGN AND METHODS - Eight healthy men (18-25 years of age) underwent ergometer training at lactate threshold (LT) intensity for 60 min/day for 5 days/week for 6 weeks. An insulin-modified intravenous glucose tolerance test was performed before as well as at 16 h and 1 week after the last training session. S-G and insulin sensitivity (S-I) were estimated using a minimal-model approach. RESULTS - After the exercise training, Vo(2max) and Vo(2) at LT increased by 5 and 34%, respectively (P < 0.05). The mild exercise training improves S-G measured 16 h after the last training session, from 0.018 +/- 0.002 to 0.024 +/- 0.001 min(-1) (P < 0.05). The elevated S-G after exercise training tends to be maintained regardless of detraining for 1 week (0.023 +/- 0.002 min(-1), P = 0.09). S-I measured at 16 h after the last training session significantly increased (pre-exercise training, 13.9 +/- 2.2; 16 h, 18.3 +/- 2.4, x 10(-5) . min(-1) . pmol/l(-1), P < 0.05) and still remained elevated 1 week after stopping the training regimen (18.6 +/- 2.2, x 10(-5) . min(-1) . pmol/l(-1), P < 0.05). CONCLUSIONS - Mild exercise training at LT improves S-G in healthy men with no change in the body composition. Improving not only S-I but also S-G through mild exercise training is thus considered to be an effective method for preventing glucose intolerance.