We investigated the existence of contralateral repeated bout effect (RBE) and tested if the attenuation of nuclear factor-kappa B (NF-κB; an important regulator of muscle inflammation) induction following eccentric exercise is a potential mechanism. Thirty-one healthy men performed two bouts of knee extension eccentric exercise, initially with one leg, and then with the opposite leg four weeks later. Vastus lateralis muscle biopsies of both exercised and control legs were taken 3 h post-exercise. Knee extension isometric and isokinetic strength (60°/sec and 180°/sec) were measured at baseline, pre-exercise, immediately post-exercise, and once/day for five days post-exercise. Serum creatine kinase (CK) activity and muscle soreness were assessed at baseline and once/day for five days post-exercise. NF-κB (p65) DNA-binding activity was measured in the muscle biopsies. Isometric strength loss was lower in Bout 2 than in Bout 1 at 24 h, 72 h, and 96 h post-exercise (p<0.05). Isokinetic strength (60°/sec and 180°/sec) was reduced less in Bout 2 than in Bout 1 at 72 h post-exercise (p<0.01). There were no significant differences between bouts for post-exercise CK activity or muscle soreness. p65 DNA-binding activity was increased following eccentric exercise (as compared to the control leg) in Bout 1 (122.9% ± 2.6%; p<0.001) and Bout 2 (109.1% ± 3.0%; p<0.05). Compared with Bout 1, the increase in NF-κB DNA-binding activity post-exercise was attenuated after Bout 2 (p = 0.0008). Repeated eccentric exercise results in a contralateral RBE, which could be due to the attenuated increase in NF-κB activity post-exercise.
- eccentric exercise
- muscle damage
- inflammatory response
- Copyright © 2013, Journal of Applied Physiology