To Örebro University

BACKGROUND: Caffeine is widely recognized as an ergogenic aid to enhance athletic performance, yet its effects in hot environments remain relatively underexplored.

AIMS: To provide a comprehensive overview of the research landscape and identify research themes in this field.

METHODS: We systematically searched the Web of Science (WoS) and SCOPUS databases using keywords related to caffeine (e.g., caffe*), hot environments (e.g., heat, hot, or therm*), and athletic performance (e.g., cardio, endurance, or strength). The Bibliometrix package in R was used for bibliometric analysis and result visualization, while a narrative review was subsequently performed to identify research themes.

RESULTS: We found that studies examining the impact of caffeine on exercise in hot conditions are relatively sparse and have progressed slowly in recent years. Research in this domain has predominantly been concentrated within an academic network led by Professor Lawrence Armstrong. Recent contributions have been sporadically made by emerging scholars, with collaborations largely confined to a few research groups and countries. Key research themes identified include exercise performance, thermoregulation, fluid balance, physiological responses, immune responses, synergistic effects with other compounds, and the influence of individual differences. Of these, the first three themes-exercise performance, thermoregulation, and fluid balance-have received the most attention.

CONCLUSIONS: Caffeine's effects on exercise performance in hot environments have not been thoroughly studied. The existing research themes are varied, and the conclusions show considerable inconsistencies. Our study highlights the need for further research into the effects of caffeine dosage, administration methods, and population-specific variables. We also call for increased collaboration among research groups to advance scientific understanding and address the gaps in this field.