A recent study involving researchers from Tunisia, Spain, and Norway explored how caffeine, melatonin, and their combined effects impact male participants during shuttle runs. The results indicated that combining these substances might enhance athletic performance, although further research is needed to understand their effects on sleep.
Melatonin is known as a chronobiotic, meaning it can help reset the body’s circadian rhythms. Additionally, it possesses antioxidant properties that assist in reducing inflammation and cellular damage, particularly in mitochondria, thereby promoting recovery after exercise.
Caffeine, a well-researched psychostimulant and ergogenic aid, is frequently utilized by athletes to boost performance. Though less extensively studied, caffeine may also exhibit antioxidant and anti-inflammatory effects.
Despite its performance-enhancing qualities, caffeine can disrupt sleep when consumed later in the day due to its action on adenosine receptors, which may adversely affect physical performance and recovery.
Given the opposing physiological effects of melatonin and caffeine, the researchers aimed to investigate the impact of administering these substances in various combinations or at different times.
The study’s results confirmed the positive effects of caffeine on athletic performance, a finding consistent with established knowledge about its influence on the nervous system. Additionally, the researchers found that combining these supplements led to enhanced performance, which they suggest could be partly attributed to melatonin’s regulatory effects on autonomic balance, as indicated by lower peak heart rate responses observed.
Study details
This randomized double-blind placebo-controlled crossover study included 14 trained male athletes who abstained from caffeine for two days prior. Participants experienced four different conditions, separated by a seven-day washout period: (1) PLA + PLA: placebo before sleep and placebo in the morning; (2) PLA + CAF: placebo before sleep and caffeine (3 mg·kg−1) in the morning; (3) MEL + PLA: melatonin (6 mg) before sleep and placebo in the morning; and (4) MEL + CAF: melatonin before sleep followed by caffeine in the morning.
Exercise testing took place one hour after ingestion in the morning. It consisted of warm-up exercises followed by a 5-meter shuttle run test (5mSRT), which included six repetitions of 30-second maximal shuttle sprints, with a 35-second passive recovery period between each sprint. Performance was measured in terms of speed, perceived exertion (RPE), heart rate, peak heart rate, and blood samples were analyzed for markers of muscle damage and inflammation.
The findings showed no significant differences in sleep quality or duration among the various conditions. Participants’ total distance in the shuttle run test improved with all active conditions compared to placebo. Additionally, the combined supplementation resulted in lower markers of muscle damage and inflammation when compared to single supplementation and placebo.
“These findings suggest that nocturnal melatonin did not significantly enhance sleep quality or quantity. However, it may positively influence subsequent high-intensity performance and alleviate physiological stress. Combining melatonin with caffeine could help maintain performance-related outcomes,” the researchers noted.
The researchers acknowledged some limitations, such as the small sample size, urging caution in interpreting the results. They also recommended that future studies explore various dosages and involve larger, more diverse populations.
Journal: Nutrients; doi: 10.3390/nu18091425; “Melatonin, Caffeine, or Their Combination: Effects on Sleep, Performance, and Perceived Exertion in a Placebo-Controlled Crossover Study.” Authors: N. Mahdi et al.
