Effect of pre-exercise caffeine intake on endurance performance and core temperature regulation during exercise in the heat: a systematic review and analysis.
Naulleau C, Jeker D, Pancrate T, Claveau P, Deshayes TA, Burke LM, Goulet EDB. Sports Med. 2022 May 26. doi: 10.1007/s40279-022-01692-1. Epub ahead of print.
Caffeine intake (6mg/kg) 1 hour before exercise in the heat has a minimal effect on improving endurance performance and increasing core body temperature.
Caffeine is an ergogenic aid; however, prior studies have led to conflicting results about the effect of caffeine during exercise in hot environmental conditions.
Naulleau and colleagues completed a systematic review and meta-analysis to assess the effect of pre-exercise caffeine intake on endurance performance and core body temperature regulation when someone exercises in the heat.
The researchers completed a comprehensive literature search. They included an article if it met five inclusion criteria: (1) placebo-controlled or randomized controlled trial study design, (2) included healthy adults, (3) studied endurance exercise for at least 20 minutes, (4) caffeine intake (swallowed without another compound) at least 30 minutes prior to exercise, (5) assessed core body temperature via rectal, esophageal, or gastrointestinal intake. The authors included 13 articles in the final systematic review. Twelve studies reported on core body temperature regulation, and 6 reported on exercise performance.
Overall, the average caffeine dose was 6mg/kg of body weight taken ~1 hour before exercise at 34oC. On average, participants exercised for ~70 minutes. The authors analyzed data from 212 participants (90% men). While caffeine had a no-to-minimal impact on exercise performance (-1 to 5% improvement), it caused a slightly greater rate of increase in core body temperature (0.10 oC/hour) compared to a placebo.
The authors demonstrated that caffeine intake had little impact on exercise performance and core body temperature changes in a hot environment. However, in some circumstances, a slight improvement in exercise performance may be beneficial. Hence, if an athlete wants to take caffeine before endurance exercise in the heat, we can at least be reassured that it is unlikely to adversely affect their core body temperature. However, we should be cautious in generalizing these results because the studies were primarily among healthy adult men. Hence, more high-quality research needs to assess caffeine in these conditions among females and younger athletes.
Sports medicine team members should be aware that caffeine’s effect on people exercising in the heat may be minimal, but we know very little about its impact on females or young athletes.
Questions for Discussion
How do you advise your athletes with regards to caffeine intake prior to exercise? Based on the conclusions of this study, would you be more or less likely to advise your athletes on the proper use of caffeine?
Written by: Kyle Harris
Reviewed by: Jeffrey Driban
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