# Acute Effects of Different Melatonin Doses on Performance and Psychophysiological Responses During Exhaustive Cycling Exercise: A Double-Blind Crossover Study

## TL;DR

This study found that taking different doses of melatonin before cycling exercise does not improve performance or affect physical or psychological responses in healthy men.

## Contribution

The novel contribution is the evaluation of acute melatonin effects on cycling performance and responses in a controlled, crossover design.

## Key findings

- Acute melatonin doses (5–20 mg) did not improve time to exhaustion during cycling.
- No significant differences in physiological or psychophysiological responses were observed between melatonin and placebo conditions.
- Baseline values were consistent across sessions, and no dose–response relationship was detected.

## Abstract

Background/Objectives: This study examined the acute effects of different doses of melatonin on performance, physiological, and psychophysiological responses during individualized exhaustive cycling exercise. Methods: Fifteen physically active but cycling-inexperienced men (18–35 years) completed a double-blind, randomized, placebo-controlled, crossover protocol. Following an incremental test to determine the anaerobic threshold (AnT), participants performed four exhaustive exercise sessions at 80% of AnT after ingesting placebo or melatonin (5, 12.5, or 20 mg), administered approximately 30 min before exercise. Time to exhaustion (TLim) was considered the primary performance outcome. Heart rate, peripheral oxygen saturation, blood lactate concentration, blood glucose, and ratings of perceived exertion were assessed before, during, and after exercise. Results: No significant differences were observed between experimental conditions for TLim or for any physiological or psychophysiological variable. Only main effects of time were detected, reflecting expected exercise-induced responses, with small effect sizes and no evidence of a dose–response relationship across melatonin conditions. Baseline values were comparable among sessions. These findings indicate that acute melatonin administration at doses ranging from 5 to 20 mg does not elicit ergogenic effects nor modulate physiological or psychophysiological responses during prolonged individualized cycling exercise in healthy individuals. Conclusions: In male, healthy, physically active individuals inexperienced in cycling, acute melatonin administration at the doses tested did not produce ergogenic effects or alter physiological and psychophysiological responses during prolonged, individualized cycling exercise.