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A Single Bout of Exercise at Higher Intensity Enhances Glucose Effectiveness in Sedentary Men

Division of Sports Medicine (Y.H., S.Nu., D.J.L., Y.T., H.O., K.To., K.Ta.), School of Comprehensive Human Science, and Institute of Health and Sport Sciences (K.To., K.Ta.), University of Tsukuba, Ibaraki 305-8574, Japan; and Division of Endocrinology and Metabolism, Department of Medicine (S.Na., N.T., I.K., S.I.), Jichi Medical School, Tochigi 329-0498, Japan

Address all correspondence and requests for reprints to: Kiyoji Tanaka, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8574, Japan. E-mail: tanaka{at}sports.taiiku.tsukuba.ac.jp.

Objective: Previous studies have shown that glucose effectiveness and insulin sensitivity are acutely enhanced by exercise at various intensities. The aim of this study was to determine the effects of a single bout of exercise at intensities recommended by the American Diabetes Association (ADA) and the American College of Sports Medicine (ACSM) on glucose uptake-specific glucose effectiveness (S_G²*) and insulin sensitivity (S_I²*). S_G²* and S_I²* were estimated by a two-compartment minimal model.

Design: Six healthy men (age, 28.5 ± 2.0 yr) performed a stable-labeled frequently sampled iv glucose tolerance test (FSIGT) under three separate conditions: without any prior exercise, and immediately after single 20-min bouts of cycle ergometer exercise at an intensity of 50% and 70% of maximal oxygen uptake (O_2max). The exercise intensities were close to the lower and upper boundaries recommended by the ADA and ACSM.

Results: Glucose disappearance constant (K_G), S_G²*, and S_I²* increased after exercise in an intensity-dependent manner. Increases in S_G²* (+237.1 ± 50.5%), S_I²* (+225.6 ± 51.9%), and K_G (+151.7 ± 16.5%) following exercise at 70% O_2max were statistically significant (P < 0.05), whereas those at 50% O_2max were not.

Conclusions: In conclusion, a single bout of exercise acutely improves S_I²* and S_G²* in individuals with normal glucose tolerance in an intensity-dependent manner.