Moderate intensity exercise reduces postprandial triacylglycerol (TG) concentrations. We tested whether this reflects increased TG clearance. Eight normotriglyceridaemic men, aged 48.3 +/- 7.3 years (mean +/- SD), performed two oral fat tolerance tests (blood samples taken in the fasted state and for six hours after a high-fat meal containing 1.00 g fat, 0.97 g carbohydrate, 58 kJ energy kg-1 fat-free body mass) and two intravenous fat tolerance tests (blood samples in the fasted state and after a bolus injection of Intralipid, 0.1 g fat kg-1 body mass). The afternoon before one oral and one intravenous test, subjects walked briskly for 90 min; no exercise was performed before the control tests. Prior exercise reduced fasting TG concentration similarly in the oral (16 +/- 7 %) (mean +/- SEM) and intravenous (18 +/- 7 %) tests, and reduced postprandial TG concentrations in the oral test by 18 +/- 6 % (all P < 0.05). However, prior exercise did not increase Intralipid clearance (disappearance curve slopes: control, 4.69 +/- 0.49 % min-1; exercise, 4.85 +/- 0.40 % min-1). These data suggest that mechanisms other than increased TG clearance mediate the lower postprandial TG concentrations seen after moderate exercise.

Purpose: To quantify net glycogen utilisation in the vastus lateralis (VL) and gastrocnemius (G) of male (n=11) and female (n=10) recreationally active runners during three outdoor training sessions. Methods: After 2 days standardisation of carbohydrate (CHO) intakes (6 g.kg -1 body mass per day), glycogen was assessed before and after 1) a 10-mile road run (10-mile) at lactate threshold, 2) 8 x 800 m track intervals (8 x 800 m) at velocity at V O2max and 3) 3 x 10 minute track intervals (3 x 10 min) at lactate turnpoint. Results: Resting glycogen concentration was lower in the G of females compared with males (P<0.001) though no sex differences were apparent in the VL (P=0.40). Within the G and VL of males, net glycogen utilisation differed between training sessions where 10-mile was greater than both track sessions (all comparisons, P<0.05). In contrast, net glycogen utilisation in females was not different between training sessions in either muscle (all comparisons, P>0.05). Net glycogen utilisation was greater in males than females in both VL (P=0.02) and G (P=0.07) during the 10-mile road run. With the exception of males during the 3 x 10 min protocol (P=0.28), greater absolute glycogen utilisation was observed in the G versus the VL muscle in both males and females and during all training protocols (all comparisons, P<0.05). Conclusion: Data demonstrate 1) prolonged steady state running necessitates a greater glycogen requirement than shorter but higher intensity track running sessions, 2) females display evidence of reduced resting muscle glycogen concentration and net muscle glycogen utilisation when compared with males and 3), net glycogen utilisation is higher in the gastrocnemius muscle compared with the vastus lateralis.

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