The Influence of Caffeine Supplementation on Resistance Exercise: A Review

Abstract

This paper aims to critically evaluate and thoroughly discuss the evidence on the topic of caffeine supplementation when performing resistance exercise, as well as provide practical guidelines for the ingestion of caffeine prior to resistance exercise. Based on the current evidence, it seems that caffeine increases both maximal strength and muscular endurance. Furthermore, power appears to be enhanced with caffeine supplementation, although this effect might, to a certain extent, be caffeine dose-and external load-dependent. A reduction in rating of perceived exertion (RPE) might contribute to the performance-enhancing effects of caffeine supplementation, as some studies have observed decreases in RPE coupled with increases in performance following caffeine ingestion. However, the same does not seem to be the case for pain perception, as there is evidence showing acute increases in resistance exercise performance without any significant effects of caffeine ingestion on pain perception. Some studies have reported that caffeine ingestion did not affect exercise-induced muscle damage but that it might reduce perceived resistance exercise-induced delayed onset muscle soreness; however, this needs to be explored further. There is some evidence that caffeine ingestion, compared to a placebo, may lead to greater increases in the production of testosterone and cortisol following resistance exercise. However, given that the acute changes in hormone levels seem to be weakly correlated with hallmark adaptations to resistance exercise, such as hypertrophy and increased muscular strength, these findings are likely of questionable practical significance. Although not without contrasting findings, the available evidence suggests that caffeine ingestion can lead to acute increases in blood pressure (primarily systolic), and, thus, caution is needed regarding caffeine supplementation among individuals with high blood pressure. In the vast majority of studies, caffeine was administered in capsule or powder forms, and therefore, the effects of alternative forms of caffeine such as chewing gums or mouth rinses on resistance exercise performance remain 3 unclear. The emerging evidence suggests that coffee might be at least equally ergogenic as caffeine alone when the caffeine dose is matched. Doses in the range of 3 to mg•kg-1 seem to be adequate for eliciting an ergogenic effect when administered 60 min pre-exercise. In general, caffeine seems to be safe when taken in the recommended doses. However, at doses as high as 9 mg•kg-1 or higher, side-effects such as insomnia might be more pronounced. It remains unclear whether habituation reduces the ergogenic benefits of caffeine on resistance exercise, as no evidence exists for this type of exercise. Caution is needed when extrapolating these conclusions to females as the vast majority of studies involved only male participants. Key points  Caffeine supplementation may acutely enhance muscular endurance, maximal strength, and power in resistance exercise.  Doses in the range 3 to 9 mg...

Acute Caffeine Supplementation Does Not Improve Performance in Trained CrossFit® Athletes

“…In this study, the effects of caffeine supplementation on CrossFit ® performance for a 20-min muscular endurance workout ("Cindy") were examined. Similar to previous investigations documenting caffeine's ergogenic effects for other types of training programs [5,31,33], it was hypothesized that caffeine supplementation would result in an increase in CrossFit ® performance during a high-volume muscular endurance workout that taxed multiple muscle groups with limited recovery, as well as a decrease in perceptual responses to exercise (i.e., perceived exertion).…”

“…The purpose of this investigation was to determine the effects of acute caffeine supplementation on CrossFit ® performance and perceptual responses to exercise in CrossFit ® -trained men. Because of the well-documented ergogenic effects of caffeine that are likely due to central mechanisms [2,3,5,42], it was hypothesized that caffeine supplementation would improve CrossFit ® performance. The hypothesis was not supported, as no significant improvement in CrossFit ® performance or perceptual responses was found after caffeine supplementation.…”

“…Support for this strategy is recognized by the International Olympic Committee and the International Society of Sports Nutrition, who both acknowledge caffeine as a dietary supplement with "good evidence" for its ergogenic effects, benefiting endurance and strength/power in athletes [2,3]. The majority of this evidence has been established utilizing singular exercise modalities when assessing muscle function (muscular strength and endurance) or exhaustive protocols (time-to-exhaustion and repeated-sprint ability) [4][5][6][7][8]. However, some athletes are not easily classified into physical demands that are strictly endurance-or strength/power-based in nature and require multiple facets of health-(e.g., aerobic capacity and muscular strength) and skill-related (e.g., agility, speed, and power) physical fitness [9].…”

“…These limitations may be resolved with larger sample sizes, using exercises that tax other aspects of muscular fitness, and greater workout durations, the latter of which may reveal caffeine's ergogenic properties [31,32]. Ostensibly, caffeine represents an ideal candidate for investigation, with "good evidence" establishing its ergogenicity across a variety of exercise protocols (e.g., endurance, high-intensity, muscular endurance, sprint performance, and maximal strength) and muscle groups [5,31,33]. However, the effects of caffeine supplementation on performance during high-volume muscular endurance workouts that tax multiple muscle groups with limited recovery remains unknown.…”

The Effects of Caffeine Ingestion on Measures of Rowing Performance: A Systematic Review and Meta-Analysis

“…The increase in V E following caffeine ingestion might not be due to caffeine per se, as it seems more likely this occurred as a consequence of the improvements in performance. This may especially be the fact if we consider that caffeine's ergogenic effect on exercise performance is mostly due to its ability to bind to adenosine receptors and increase motor unit recruitment [2,25].…”