Impact of Eccentric or Concentric Training on Body Composition and Energy Expenditure
Résumé
PURPOSE: To compare the effects of 8-week eccentric (ECC) versus concentric (CON) training using downhill and uphill running in rats on whole body composition, bone mineral density (BMD), and energy expenditure (EE). METHODS: Animals were randomly assigned to one of the following groups: 1) control (CTRL), 2) +15% uphill-running slope (CON), 3) -15% downhill-running slope (ECC15) and 4) -30% downhill-running slope (ECC30). Those programs enabled to achieve conditions of iso-power output for CON and ECC15 and of iso-oxygen uptake (VO2) for CON and ECC30. Trained rats ran 45min at 15 mmin five times per week. Total (TBM), fat (FBM) and lean (LBM) body mass measured through EchoMRI, and 24-hour EE including basal metabolic rate (BMR) assessed using PhenoMaster/LabMaster cage system were obtained before and after training. At sacrifice, the right femur was collected for bone parameters analysis. RESULTS: While TBM increased in all groups over the 8-week period, almost no change occurred for FBM in exercised groups (CON: -4.8+/-6.18 g; ECC15: 0.6+/-3.32 g; ECC30: 2.6+/-6.01 g). The gain in LBM was mainly seen for ECC15 (88.9+/-6.85 g) and ECC30 (101.6+/-11.07 g). ECC was also seen to positively affect BMD. An increase in BMR from baseline was seen in exercise groups (CON: 13.9+/-4.13 kJ.day; ECC15: 11.6+/-5.10 kJ.day; ECC30: 18.3+/-4.33 kJ.day) but not in CTRL one. This difference disappeared when BMR was normalized for LBM. CONCLUSIONS: Results indicate that for iso-VO2 training, the impact on LBM and BMD is enhanced with ECC as compared to CON, and that for iso-power but lower VO2 ECC, an important stimulus for adaptation is still observed. This provides further insights for the use of ECC in populations with cardiorespiratory exercise limitations.