Melatonin may have detrimental effects on the delayed-0nset muscle soreness

Melatonin is the hormone with different physiological effects, especially on analgesic and anti-inflammatory properties. contradictory reports published on the effect of melatonin on exercise performance. The present study attempt aimed to determine the effect of one-week oral administration of melatonin on delayed-onset muscle soreness (DOSM).  In this semi-experimental study, 24 healthy male subjects randomly divided into experimental and control groups. The experimental group received 6 mg per day melatonin, seven days before eccentric exercise and control group similarly received placebo. Muscle soreness produced in both feet during descending from a 50 cm bench. Serum Lactate dehydrogenase (LDH) and Creatine phosphokinase (CPK) concentration and total Antioxidant capacity (TAC) as well as the Visual Analogue Scale (VAS) of the pain and pressure pain, 7 days before eccentric protocol and 24, 48 and 72 hours after that were measured. Repeated measure analysis of variance (ANOVA) with Bonferroni comparison between two groups in each time was employed at p CPK concentration was significantly increased in the placebo group when compared before and 24 hours after DOMS (P<0.001). Perceived pain and pressure pain, 7 days before protocol and 24 and 48 hours after protocol were significantly higher in the experimental group (P<0.01). The results of this study indicated no significant increase in the TAC and the same oral supplementation with melatonin consumption (6 mg per day for seven days) had no positive effect on TAC and the biochemical and clinical symptoms of the DOMS, therefore it seems melatonin increases pain in the DOMS.