HIGHLIGHTED TOPIC Eccentric Exercise A contralateral repeated bout effect attenuates induction of NF- B DNA binding following eccentric exercise

Xin L, Hyldahl RD, Chipkin SR, Clarkson PM. A contralateral repeated bout effect attenuates induction of NFB DNA binding following eccentric exercise. J Appl Physiol 116: 1473–1480, 2013. First published August 15, 2013; doi:10.1152/japplphysiol.00133.2013.—We investigated the existence of contralateral repeated bout effect and tested if the attenuation of nuclear factor-kappa B (NFB; 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 4 wk later. Vastus lateralis muscle biopsies of both exercised and control legs were taken 3 h postexercise. Knee extension isometric and isokinetic strength (60°/sec and 180°/sec) were measured at baseline, pre-exercise, immediately postexercise, and 1/day for 5 days postexercise. Serum creatine kinase (CK) activity and muscle soreness were assessed at baseline and 1/day for 5 days postexercise. NFB (p65) DNA-binding activity was measured in the muscle biopsies. Isometric strength loss was lower in bout 2 than in bout 1 at 24, 72, and 96 h postexercise (P 0.05). Isokinetic strength (60°/s and 180°/s) was reduced less in bout 2 than in bout 1 at 72 h postexercise (P 0.01). There were no significant differences between bouts for postexercise CK activity or muscle soreness. p65 DNA-binding activity was increased following eccentric exercise (compared with 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 NFB DNA-binding activity postexercise was attenuated after bout 2 (P 0.0008). Repeated eccentric exercise results in a contralateral repeated bout effect, which could be due to the attenuated increase in NFB activity postexercise.