Source credit: PubMed record for Guan et al., published in the Journal of the International Society of Sports Nutrition; DOI: 10.1080/15502783.2026.2692017.
A new systematic review and meta-analysis in the Journal of the International Society of Sports Nutrition looked at randomized trials that manipulated the serotonergic system in healthy adults to study exercise performance and central fatigue. The review found outcome-specific signals, including small changes in motor response, EMG, heart rate, and blood glucose, while obvious performance and perceived-effort outcomes were more mixed.
Why it matters for lifters
For bodybuilders and strength athletes, the useful takeaway is not to chase serotonin-related drugs or supplement claims. It is that central fatigue is complicated: brain chemistry, muscle output, heart-rate response, fueling, sleep, heat, and session design can all shape how hard a set or conditioning block feels. If a product claims to “hack” fatigue with one pathway, this review is a reason to be skeptical.
Practical programming still comes back to controllable basics: keep hard sets high quality, manage failure work, separate heavy lower-body training from demanding conditioning when needed, and treat persistent unusual fatigue as a recovery or medical signal rather than a willpower problem.
What to watch next
Watch for larger trials that connect central-fatigue markers to real training outcomes such as completed volume, repeat-sprint output, strength retention late in a workout, or recovery between sessions. Also watch how sports-nutrition companies frame this research, because a mechanistic fatigue signal is not the same thing as proof that a consumer product improves performance.
Health disclaimer: This article is for informational purposes only and is not medical advice. Do not use prescription medicines, serotonin-active compounds, or supplement strategies to alter fatigue or performance without guidance from a qualified health professional.