madman
Super Moderator
14 Conclusions
Current evidence suggests that caffeine ingestion increases maximal strength, as assessed by 1RM and MVC tests, and muscular endurance. Furthermore, studies show that power is enhanced by caffeine supplementation, although this effect might be caffeine dose- and external load-dependent. While a reduction in RPE potentially contributes to the performance-enhancing effects of caffeine supplementation, the same was not found for pain perception. Some studies have reported that caffeine ingestion did not affect exercise induced muscle damage, but that it might even reduce resistance exercise-induced DOMS. There is some evidence that caffeine ingestion, compared with placebo, leads to greater increases in the production of testosterone and cortisol following resistance exercise. However, given that the acute changes in hormone levels are weakly correlated with long term 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 the effects of alternative forms such as chewing gums or mouth rinses on resistance exercise performance therefore remain unclear. The emerging evidence suggests that coffee is at least equally ergogenic as caffeine alone when the caffeine dose is matched. Nevertheless, more research is needed on this topic. Doses in the range of 3–9 mg·kg−1 seem to be adequate for eliciting an ergogenic effect when administered 60 min pre-exercise. It remains unclear what the minimal effective doses are for different types of resistance exercise.
In general, caffeine was found 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 are more pronounced, which needs to be considered when prescribing caffeine supplementation. It remains unclear whether habituation cancels out the ergogenic benefits of caffeine on resistance exercise performance as no evidence exists for this type of exercise. In some cases, administering placebo alone with the suggestion that it is caffeine has also been shown to enhance performance and reduce RPE. Therefore, the effectiveness of the blinding needs to be considered in future research. Caution is needed when extrapolating these conclusions to females as the vast majority of studies involved only male participants. Finally, most of the studies conducted in this area report small-to-moderate acute improvements in resistance exercise performance with caffeine ingestion. Therefore, future long-term intervention studies are needed to explore if such acute increases in performance with caffeine ingestion also impact long-term adaptations to resistance exercise.
Key Points
Caffeine supplementation may acutely enhance muscular endurance, maximal strength, and power in resistance exercise.
Doses in the range of 3–9 mg·kg−1 seem to be adequate for eliciting ergogenic effects. Caffeine seems to be generally safe when taken in these doses; however, at doses as high as 9 mg·kg−1 or higher, side effects might be more pronounced.
Blood pressure may be increased following caffeine ingestion, and therefore caution is needed regarding caffeine supplementation among individuals with high blood pressure.
The mechanism by which caffeine intake affects resistance exercise performance is likely multifactorial.
Current evidence suggests that caffeine ingestion increases maximal strength, as assessed by 1RM and MVC tests, and muscular endurance. Furthermore, studies show that power is enhanced by caffeine supplementation, although this effect might be caffeine dose- and external load-dependent. While a reduction in RPE potentially contributes to the performance-enhancing effects of caffeine supplementation, the same was not found for pain perception. Some studies have reported that caffeine ingestion did not affect exercise induced muscle damage, but that it might even reduce resistance exercise-induced DOMS. There is some evidence that caffeine ingestion, compared with placebo, leads to greater increases in the production of testosterone and cortisol following resistance exercise. However, given that the acute changes in hormone levels are weakly correlated with long term 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 the effects of alternative forms such as chewing gums or mouth rinses on resistance exercise performance therefore remain unclear. The emerging evidence suggests that coffee is at least equally ergogenic as caffeine alone when the caffeine dose is matched. Nevertheless, more research is needed on this topic. Doses in the range of 3–9 mg·kg−1 seem to be adequate for eliciting an ergogenic effect when administered 60 min pre-exercise. It remains unclear what the minimal effective doses are for different types of resistance exercise.
In general, caffeine was found 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 are more pronounced, which needs to be considered when prescribing caffeine supplementation. It remains unclear whether habituation cancels out the ergogenic benefits of caffeine on resistance exercise performance as no evidence exists for this type of exercise. In some cases, administering placebo alone with the suggestion that it is caffeine has also been shown to enhance performance and reduce RPE. Therefore, the effectiveness of the blinding needs to be considered in future research. Caution is needed when extrapolating these conclusions to females as the vast majority of studies involved only male participants. Finally, most of the studies conducted in this area report small-to-moderate acute improvements in resistance exercise performance with caffeine ingestion. Therefore, future long-term intervention studies are needed to explore if such acute increases in performance with caffeine ingestion also impact long-term adaptations to resistance exercise.
Key Points
Caffeine supplementation may acutely enhance muscular endurance, maximal strength, and power in resistance exercise.
Doses in the range of 3–9 mg·kg−1 seem to be adequate for eliciting ergogenic effects. Caffeine seems to be generally safe when taken in these doses; however, at doses as high as 9 mg·kg−1 or higher, side effects might be more pronounced.
Blood pressure may be increased following caffeine ingestion, and therefore caution is needed regarding caffeine supplementation among individuals with high blood pressure.
The mechanism by which caffeine intake affects resistance exercise performance is likely multifactorial.
