Effect of acute melatonin administration on physiological response to prolonged exercise

Abstract

Exogenous melatonin supplementation may enhance endurance performance because of its pre-cooling effect. The present study aimed to evaluate the effect of acute melatonin ingestion on rectal temperature (Tre) response to submaximal exercise performed in moderate temperature. Eight students moderately trained aged between 20–23 years completed two experimental sessions in a randomized order. The subjects ran on a treadmill for 45 minutes at 60% of their maximal aerobic speed (MAS) after either melatonin-(6mg) or placebo ingestion. Tre, heart rate (HR), thermal sensation (TS) and rating of perceived exertion (RPE) were measured. Blood samples were taken before and after exercise to measure the hemoglobin (Hb), hematocrit (Hct), sodium (Na+) and potassium (K+) concentrations. Melatonin decreased resting Tre by ≈ 0.2°C, but it did not attenuate the increase in core temperature during exercise. At the end of the exercise, HR was significantly attenuated in melatonin condition compared with placebo condition. High dose of melatonin (>5 mg) is not recommended to attenuate the increase of core temperature during continuous exercise. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.