Can Caffeine Improve Muscular Strength & Power Performance?

Caffeine in exercise/ sport
We here at OUTWRK have our own mini mount Rushmore of ergogenic (performance enhancing) aids. The three Cs - carbohydrates, creatine and caffeine. These three consumables all have a fairly extensive library of research supporting their use in improving exercise and sporting performance. For the sake of this article we will be solely focusing on caffeine. Whilst caffeine has been found to significantly improve muscular endurance, aerobic exercise performance (Ganio et al. 2009 ) and lower ratings of perceived exertion and pain (Astorino et al. 2011, Gliottoni et al. 2009), it's effect on maximal strength and power output remain uncertain.
Many sports and various forms of exercise activity require a performer to be able to incorporate and seamlessly transition across these various modalities without a compromise in performance. One moment the focus could be on a more aerobic focused element and then the performer may be required to perform a ballistic movement (or a number of these movements in rapid succession).
An example could be extrapolated from a game of rugby; a player may need to jog/run to get into a defensive backline position and then is required to make a tackle on an opposition player (where the goal is to either halt their progress immediately and or move them backwards to stop the opposing team "getting on the front foot"). If a player is unable to perform either modality to the required standard then a negative outcome could result - either the player could be called offside, not be in position to make the tackle and or if they do make the tackle they are unable to complete it and the opposing player breaks away and or the tackle is made but progress is not halted and the opposing team now have momentum in their attack. The necessity to be able to transition between the various performance related modalities is clear and the more skilled the individuals are performing the smaller the margin for error. This is why athletes look for aids which can improve performance, the smallest percentage of improvement can have a significant impact on the resulting outcome.
Caffeine in drug tested competition
It should be noted that caffeine is not on WADA's (World Anti-Doping Agency) prohibited substance list (both in and outside of performance) however is currently on their 2018 Monitoring Program (which is used to evaluate misuse of certain substances in sport) and so advice surrounding caffeine intake could be subject to change. When caffeine was more heavily regulated (meaning failed drug tests past a certain limit) the limit for intake was around 12 microgram per ml of urine. To put that into perspective (meaning essentially how worried you should be if you have a cup of coffee before a workout), that level would require the ingestion of around eight cups of espresso. Hopefully no one needs that amount of caffeine to go train or perform, although in saying that we need about ten some days, especially after squats and metcon the day before...
Recent findings
As mentioned, the focus of this article will be to evaluate the effectiveness of caffeine in improving maximal strength and power output performance. Previous research has yielded conflicting results on the subject. A recently published systematic review and meta-analysis (Grgic et al. 2018) aimed to proved clarity on the issue and summarized the results from individual studies on the effects of caffeine intake on muscle strength and power in their paper.
The Study
They conducted a search to find studies on the effects of caffeine on: (i) maximal muscle strength measure using one repetition maximum tests; and (ii) muscle power assessed by tests of vertical jumps. Skeletal muscle power is a well-known predictor of sports performance however direct measurement is difficult. Vertical jumps are employed as, although power and jumping are not identical, correlations link them to success in a variety of sports. Ten studies on the strength outcome (149 total participants) and ten studies on the power outcome (145 total participants) met the inclusion criteria for the meta-analyses.
Their Results
  • The results achieved showed that caffeine ingestion improved both strength and power significantly.
  • They also found that caffeine significantly improved upper body strength but not lower. Two included studies however did find improvement using the barbell back squat. It it worth nothing that the included studies did not report on the reliability of their strength assessment tests.
  • They found no significant difference in maximal strength testing following caffeine intake in trained vs untrained individuals (although trained individuals have reportedly seen significant improvements over untrained in previous studies). This may be limited by a small sample size (n=32).
  • The caffeine ingestion in the studies ranged from 0.9 to 7mg per kg.
  • They did find that males showed a significant improvement in strength with caffeine ingestion however the subgroup analysis for females was limited by a small sample size and not adequately reflect caffeine as an ergogenic aid for females when testing these two measures.
  • Improvements in performance measures were found in both habitual (up to 600mg a day) and non-habitual caffeine drinkers.
Practical applications
What are the practical applications of these findings? Well, first and foremost, this indicates that caffeine may be a useful aid in improving maximal strength and power. This can be applied both in competitive and recreational settings. The exact mechanisms of how caffeine improves performance outcomes is not fully understood. Caffeine may exert its effect through antagonism of the adenosine receptors in the brain – a pathway that leads to an increased production of adrenalin, which stimulates energy production and improves blood flow to the muscles and heart. Another theory is that it comes as a result of the increase in alertness, mood, cognitive processes and vigilance. Ingestion of caffeine up to 200mg has been shown to elicit these responses and may be a useful addition to training for both recreational and competitive exercisers/athletes. This can be a cup of black coffee, a number of pre-workout supplements or a calorie/sugar free energy drink. It should be noted that over ingestion of caffeine can be of detriment to performance, however determining what would be over consumption is difficult and highly varied. Our recommendations would be to trial black coffee before exercise (in varying strengths) before considering using another form or source of caffeine. For most, a black coffee before training and or a sports event is more than enough and should elicit some improvement in performance.
Caffeine has a significant effect on improving maximal strength and muscular power output. Practical implications for this would be a black coffee or other caffeine source before training/competition to gauge it's relative effect for a given person. It may be a useful method to gain an advantage in/improve exercise/sporting performance however is not a prerequisite and shouldn't be treated as such. Advising the use of should be handled on a case by case basis (depending on athlete preference, sustainability of use etc.) and background medical checks should be performed first to gauge the safety of use.
Additional Reading
Astorino T.A. et al. (2011) Effect of caffeine intake on pain perception during high-intensity exercise.Int J Sport Nutr Exerc Metab, 21(1):27-32.
Ganio M. S. et al. (2009) Effect of Caffeine on Sport-Specific Endurance Performance: A Systematic Review.J Strength Cond Res, 23(1):315-24.
Gliottoni R.C. et al. (2009) Effect of Caffeine on Quadricep Pain During Acute Cycling Exercises in Low Versus High Caffeine Consumers. Sport Nutr Exer Metab, 19:150-161
Grgic, J., Trexler, E., Lazinica, B. and Pedisic, Z. (2018). Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis. Journal of the International Society of Sports Nutrition, 15(1).

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