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-dependent and -independent mechanisms. We evaluated whether these two effects of exercise on glucose disposal can be detected with the minimal model technique. Seven healthy volunteers were submitted at random order to two frequently sampled intravenous glucose tolerance test (FSIVGTTs), one at rest and the other 25 minutes after a 15-minute exercise test. This exercise included 5 minutes of increasing workload on a cycloergometer followed by 10 minutes at 85% of the maximal theoretic heart rate. Bergman's minimal model of insulin action was used to analyze the two FSIVGTTs and produced the following parameters: coefficient of glucose tolerance (Kg), ie, the slope of the exponential decrease in glycemia between 4 and 19 minutes after intravenous glucose; insulin sensitivity (Sl); and glucose effectiveness at basal insulin (Sg). Sg was divided into its two components: basal insulin effectiveness ([BIE] Sl x basal insulin) and glucose effectiveness at zero insulin ([GEZI] Sg-BIE). After the exercise bout, subjects had an increased Kg (3.44 +/- 0.44 v 2.06 +/- 0.28 x 10(-2).min-1, P < .02), Sl (11.43 +/- 1.27 v 6.23 +/- 0.97 x 10(-4) microU/mL.min-1, P < .01), and Sg (4.40 +/- 0.55 v 2.81 +/- 0.36 x 10(-2).min-1, P < .02). The increase in Sg 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 increase in BIE (0.80 +/- 0.12 v 0.47 +/- 0.08 x 10(-2).min-1, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)