Metabolic responses to exercise on land and in water following glucose ingestion.
The aim of this study was to compare whole-body glucose uptake in cycling and running performed during physiological hyperinsulinaemia. On three occasions, seven male subjects underwent a hyperinsulinaemic (30 mU m−2 min−1), euglycaemic (5 mmol l−1) clamp for 120 min. On one occasion, subjects rested for the duration of the trial (CON). On the other two occasions, after an initial resting period of 30 min, subjects either cycled (CYC) or ran (RUN) for 90 min at 65% of maximal O2 uptake (V̇O2max). Insulin infusion resulted in physiological hyperinsulinaemia that was maintained for the duration of each trial [CON: 61 (3) mU l−1; CYC: 77 (7) mU l−1; RUN: 77 (5) mU l−1]. The rate of glucose uptake was greater during RUN than during CYC [last 30 min of exercise: 140 (4) vs 109 (8) μmol kg−1 min−1, respectively; P <0.01]. A differential amount of active muscle mass and/or muscle fibre type recruitment might account for the observed differences in glucose disposal between cycling and running.