In 2004 the World Anti-Doping Agency (WADA) removed caffeine from its list of banned substances due in part to the stimulant’s ubiquitous presence in a variety of foods, drinks, and other nutritional products. The naturally occurring substance was simply too commonplace to police effectively. Since then, caffeine has found its way into almost every type of sports supplement, including energy bars, gels, pre- and post-workout shakes, pills, and even chewing gum. So just what benefit does caffeine offer that prompted WADA to list it alongside other vilified performance-enhancing drugs (PEDs) with scary names such as oxandrolone or stanozolol? In short, research has shown caffeine significantly improves performance in sustained endurance activities that predominantly utilize the aerobic metabolic pathways. These include continuous efforts lasting longer than a few minutes such as running, swimming, cycling, and probably even longer CrossFit WODs. According to a review of caffeine research, the stimulant provides an average 3% performance increase over placebo in endurance time-trials (Ganio et al., 2008). However, while most studies agree that caffeine provides a clear endurance benefit, the magnitude of enhancement will vary significantly depending on individual factors such as regular consumption habits, amount ingested, and ingestion timing. For example, consuming coffee or caffeine on a daily basis will limit the performance benefit of an acute dosage since the body is habituated to the stimulant’s effects. Regular caffeine habits also may portend a temporary drop in performance if the athlete ceases consumption abruptly. To fully optimize any ergogenic effect, most researchers recommend abstaining from caffeine for at least a few days before a targeted exercise bout or competition. Typical ergogenic doses fall within 2-9 milligrams per kilogram of bodyweight, although most studies used around 4-6 mg/kg, thereby minimizing potential negative side effects from too much caffeine such as nervousness, gastrointestinal distress, and headaches. For a 70 kg (155 lb.) person, the high-end dose of 6 mg/kg (420 mg total) would represent 4-5 cups of black coffee or roughly five 8 oz. Red Bull energy drinks. Caffeine is completely absorbed within 45 minutes after ingestion, meaning that the optimal time for consumption is about an hour before exercise or competition. The stimulant’s half-life – the time it takes for the body to eliminate only one-half of the initial caffeine concentration – ranges from 4-6 hours, which explains why a late afternoon cup of coffee can lead to sleeplessness later that evening. With all that being said, coaches and athletes should be wary of drastically changing dietary routines immediately before an important competition. As I always tell athletes, competition is not the place to experiment with massive amounts of Red Bull or Monster Energy, especially if the athlete does not normally consume energy drinks. Although caffeine’s ergogenic effect in endurance events is widely supported, the stimulant’s effect on anaerobic performance is less clear. This equivocality is somewhat unexpected considering the prevalence of caffeine in pre-workout supplements intended for anaerobic activities such as sprinting or resistance training. Astorino and Roberson (2010) showed that caffeine could have a positive effect on short-term high-intensity exercise but that the benefits are far less definitive than those seen with endurance exercise. Additionally, caffeine’s effect on resistance training may actually mimic its endurance benefits. In other words, caffeine is more likely to improve muscular endurance – the number of repetitions completed during a submaximal lifting task – rather than muscular strength – the maximum weight lifted during a 1-Repetition Maximum (1RM) test. Thus, caffeine may help you complete more rounds in a kettlebell-based AMRAP but probably will not help you set a new maximum in your squat. Acute creatine supplementation would be a better way to target improvements in muscular strength. Irrespective of these differences there are several hypotheses on the biological mechanism of caffeine’s performance enhancement. One theory posits that caffeine increases the usage of fat as a fuel source, which spares vital carbohydrate stores within the muscle and delays fatigue during an endurance event. Additionally, as a stimulant of the central nervous system (CNS), caffeine acts as an antagonist of adenosine, a fatigue-inducing compound that accumulates during strenuous exercise. Caffeine also contributes to dilated blood vessels and triggers the release of catecholamines such as adrenaline, both of which are processes beneficial to athletic performance. -Matt Crockett CSCS, USAW, RKC Astorino & Roberson (2010). Efficacy of acute caffeine ingestion for short-term high-intensity exercise performance: A systematic review. Journal of Strength and Conditioning Research, 24(1), 257-265. Ganio, Klau, Casa, Armstrong, & Maresh (2009). Effect of caffeine on sport-specific endurance performance: A systematic review. Journal of Strength and Conditioning Research, 23(1), 315-324.