Purpose: To compare concentric and eccentric cycling performed by older adults for metabolic demand and post-exercise oxidative stress, inflammation and muscle damage.
Methods: Eight male and two female healthy older adults (60.4 ± 6.8 years) performed 30 min of moderate-intensity concentric (CONC-M: 50% maximum power output; POmax) and eccentric cycling (ECC-M: 50% POmax) and high-intensity eccentric cycling (ECC-H: 100% POmax) in a randomized order. Average power output (PO), oxygen consumption (VO2), heart rate (HR) and rate of perceived exertion were recorded during cycling. Some indirect markers of muscle damage were assessed before, and immediately, 24 and 48 h after cycling. Markers of oxidative stress (malondialdehyde: MDA, protein carbonyl), antioxidant (total antioxidant capacity, glutathione peroxidase activity: GPx) and inflammation (IL-6, TNF-α) were measured before and 5 min after cycling.
Results: PO in ECC-H (202.6 ± 78.5 W) was > 50% greater (P < 0.05) than that of CONC-M (98.6 ± 33.1 W) and ECC-M (112.0 ± 42.1 W). VO2 and HR were also greater (P < 0.05) for ECC-H than CONC-M (50% and 17%, respectively) and ECC-M (40% and 23%, respectively). Muscle strength loss at 1 day post-exercise (8-22%), peak soreness (10-62 mm) and creatine kinase activity (30-250 IU/L) after ECC-H were greater (P < 0.05) than those after ECC-M and CONC-M. MDA decreased (P < 0.05) after CONC-M (- 28%) and ECC-M (- 22%), but not after ECC-H. GPx activity increased after all exercises similarly (20-27%). IL-6 increased (P < 0.05) only after ECC-H (18%).
Conclusion: Oxidative stress was minimal after eccentric cycling, but high-intensity eccentric cycling induced moderate muscle damage and inflammation, which is not desirable for older individuals.
Keywords: Creatine kinase; Interleukin 6; Lengthening muscle action; Muscle soreness; TBARS; TNF alpha; Total antioxidant capacity.