Muscle soreness-induced reduction in force generation is accompanied by increased nitric oxide content and DNA damage in human skeletal muscle

We examined the effect of exercise-induced muscle soreness on maximal force generation, tissue nitric oxide (NO) and 8-hydroxydeoxyguanosine (8- OHdG) content in human skeletal muscle. Female volunteers were assigned to control (C) and muscle soreness (MS) groups (n = 6 in each). MS group performed 200 eccentric muscle actions of the rectus femoris to induce muscle soreness. Maximal force generation was measured 24 h before and after exercise in both groups. Needle biopsy samples were assayed for NO content with electron spin resonance spectroscopy after ex vivo spin trapping, and 8- OHdG content were measured with an enzyme-linked immunoassay. Maximal force decreased by 11 ± 5.4% (p < .05) 24 h after exercise in MS group. Muscle soreness increased NO and 8-OHdG contents from their control values of 0.39 ± 0.08 arbitrary units and 0.035 ± 0.004 pmol/μmol DNA to 0.96 ± 0.05 (p < .05) arbitrary units and 0.044 ± 0.005 (p < .05) pmol/μmol DNA, respectively. This is the first demonstration that muscle soreness-induced decrease in maximal force generation is a result of an increase in muscular NO content and associated with enhanced formation of 8-OHdG in human skeletal muscle.