INFLUENCE OF SHORT-TERM SUBMAXIMAL EXERCISE ON PARAMETERS OF GLUCOSE ASSIMILATION ANALYZED WITH THE MINIMAL MODEL

After exercise, glucose uptake in tissues increases by insulin-depende nt and -independent mechanisms. We evaluated whether these two effects of exercise on glucose disposal can be detected with the minimal mode l technique. Seven healthy volunteers were submitted at random order t o two frequently sampled intravenous glucose tolerance tests (FSIVGTTs ), one at rest and the other 25 minutes after a 15-minute exercise tes t. This exercise included 5 minutes of increasing workload on a cycloe rgometer followed by 10 minutes at 85% of the maximal theoretic heart rate. Bergman's minimal model of insulin action was used to analyze th e two FSIVGTTs and produced the following parameters: coefficient of g lucose tolerance (K-g), ie, the slope of the exponential decrease in g lycemia between 4 and 19 minutes after intravenous glucose; insulin se nsitivity (S-I); and glucose effectiveness at basal insulin (S-g). S-g was divided into its two components: basal insulin effectiveness ([BI E] S-I x basal insulin) and glucose effectiveness at zero insulin ([GE ZI] S-g - BIE). After the exercise bout, subjects had an increased K-g (3.44 +/- 0.44 v 2.06 +/- 0.28 x 10(-2). min(-1), P < .02), S-I (11.4 3 +/- 1.27 v 6.23 +/- 0.97 x 10(-4) mu U/mL . min(-1). P < .01), and S -g (4.40 +/- 0.55 v 2.81 +/- 0.36 x 10(-2). min(-1), P < .02). The inc rease in S-g was mainly explained by a 60% increase in GEZI (3.6 +/- 0 .57 v 2.25 +/- 0.36 x 10(-2). min(-1), P < .02), but also by an increa se in BIE (0.80 +/- 0.12 v 0.47 +/- 0.08 x 10(-2). min(-1), P < .05). Thus, a FSIVGTT sensitively detects an acute increase in glucose assim ilation after exercise, as demonstrated by an increase in K-g and its two components S-I and GEZI. GEZI seems to provide a measurement of th e non-insulin-mediated recruitment of glucose transporters in exercise d muscles. In addition, FSIVGTT protocols have to be carefully standar dized for previous exercise, since minimal model measurements are sens itive to these acute effects of muscular activity. Copyright (C) 1995 by W.B. Saunders Company