Prior exercise and postprandial substrate extraction across the human leg

Prior exercise decreases postprandial plasma triacylglycerol (TG) concentra tions, possibly through changes to skeletal muscle TG extraction. We measur ed postprandial substrate extraction across the leg in eight normolipidemic men aged 21-46 yr. On the afternoon preceding one trial, subjects ran for 2 h at 64 +/- 1% of maximal oxygen uptake (exercise); before the control tr ial, subjects had refrained from exercise. Samples of femoral arterial and venous blood were obtained, and leg blood flow was measured in the fasting state and for 6 h after a meal (1.2 g fat, 1.2 g carbohydrate/kg body mass) . Prior exercise increased time averaged postprandial TG clearance across t he leg (total TG: control, 0.079 +/- 0.014 ml.100 ml tissue(-1).min(-1); ex ercise, 0.158 +/- 0.023 ml.100 ml tissue(-1).min(-1), P < 0.01), particular ly in the chylomicron fraction, so that absolute TG uptake was maintained d espite lower plasma TG concentrations (control, 1.53 +/- 0.13 mmol/l; exerc ise, 1.01 +/- 0.16 mmol/l, P < 0.001). Prior exercise increased postprandia l leg blood flow and glucose uptake (both P < 0.05). Mechanisms other than increased leg TG uptake must account for the effect of prior exercise on po stprandial lipemia.