Effects of acute melatonin and caffeine supplementation on sleepiness and performance in trained runners

Abstract Sports nutrition, which uses ergogenic substances, has emerged as an important tool that favors athletes’ performance. Like caffeine, melatonin has been investigated as a potential ergogenic aid; however, its effects are not yet fully understood. This study aimed to evaluate the effects of acute melatonin and caffeine intake on performance and sleepiness of runners in the 1 mile physical test. A total of 24 healthy, active, and experienced male runners were selected. Participants completed a 1 mile run under three supplementation conditions (placebo, melatonin, and caffeine), each separated by a 1 week washout period. All evaluations were carried out at the same time. Sleepiness was assessed for 5 h after each supplementation. The results showed that performance over 1 mile across the three supplementation conditions did not differ. Melatonin consumption maintained an increase in sleepiness up to 5 h after the test. These findings caution against melatonin for performance, particularly when used outside its sleep-promoting context.