Abstract

This study compared concentric cycling (CONC) and two bouts of eccentric cycling (ECC1, ECC2) for substrate utilisation and resting energy expenditure (REE). Ten men (28 +/- A 8 years) performed each cycling bout for 30 min at 60 % of maximal concentric power output, with 2 weeks between bouts. Fat and carbohydrate (CHO) utilisation were assessed during and after cycling, and REE was measured before and 2 days after CONC, and before, 2 and 4 days after ECC1 and ECC2, using indirect calorimetry. An oral glucose tolerance test was performed before and 1 day after CONC, and before and 1 and 3 days after ECC1 and ECC2, and both peak and area-under-the-curve (AUC) of the glucose concentration were compared between bouts. Energy expenditure and CHO utilisation during cycling were 36 and 42 % less in ECC1, and 40 and 52 % less in ECC2, than CONC (P < 0.05). Fat utilisation was greater during ECC1 (72 %) and ECC2 (85 %) than CONC, and 48 % greater during ECC2 than ECC1 (P < 0.05). Post-exercise energy expenditure and fat utilisation were less for ECC1 than CONC (30 and 52 %, respectively), but similar between CONC and ECC2. REE did not change from baseline after any bouts. Peak and AUC glucose concentration decreased 3 days after ECC1, but no changes were evident after CONC or ECC2. These results show greater fat utilisation during eccentric than concentric cycling at the same workload, and greater fat oxidation during and after secondary eccentric cycling bout without glucose uptake impairment.