Energy expenditure and substrate oxidation during and after eccentric cycling
Faculty of Health, Engineering and Science
Centre for Exercise and Sports Science Research
Purpose: This study compared concentric cycling (CONC) and two bouts of eccentric cycling (ECC1, ECC2) for substrate utilisation and resting energy expenditure (REE). Methods: Ten men (28 ± 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. Results: 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. Conclusion: 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.