Caffeine is a legal performance-enhancing drug. In fact, it's even on the WADA's monitoring program for possible in-competition abuse. Caffeine has been shown to have performance-enhancing effects physically, mentally and metabolically. But caffeine also has some downsides if used improperly. These include anxiety, sleep deprivation and an elevated heartbeat.
The most common dietary sources of caffeine include coffee, teas and chocolate. It's important for athletes to know the basics of how caffeine is processed in the body to get a better understanding of the proper ways to use coffee for sports performance without impacting their sleep or cortisol levels.
Understanding some of the basic pharmacokinetics of caffeine is important, knowing how much to use it when to use it, and your body's response can help you utilize caffeine as a performance booster while minimizing its negative effects.
Caffeine takes about five hours to metabolize in the body. Of course this varies among individuals as some are more sensitive than others (and a tolerance can be developed over time resulting in a need for larger dosages to get the same effect as before). The CYP1A2 gene is the gene primarily responsible for influencing how effectively we break down caffeine. Stimulatory effects may begin as early as 15 minutes after ingestion but normally takes about 30-60 minutes for levels to peak. Athletes see benefits with dosages from 3-6 mg/kg of body weight.
Caffeine consumption is associated with ergogenic effects for endurance, high intensity and power performance markers. In endurance-based activities it's effective for increasing VO2, reducing time trial events and aiding with prolonged exercise. For high-intensity activities, it's been shown to increase peak power and work capacity.
- Caffeine ingestion was found to have a beneficial effect on maximal velocity contraction strength and muscular endurance.
- Caffeine ingestion resulted in greater amount of sprint work performed during a training session and greater peak power score during sprints.
- Consuming a beverage containing caffeine prior to performing ballistic bench press throws resulted in a significant increase in peak power, peak force and peak velocity.
- A study compared the effects of consuming a caffeine drink on muscle performance by comparing a control drink (no caffeine), a 1mg-per-kg of body weight caffeine drink and a 3-mg-per-kg of body weight caffeine drink. The 3-mg-per-kg of body weight caffeine drink significantly increased maximal power in the half squat and bench press.
- A study on males and females ingesting Turkish coffee an hour before exercise noted that caffeine consumption resulted in significant improvements in reaction time
- A study on the effects of caffeine consumption on well-trained middle distance runners during 1500m running was conducted. The ingestion of caffeine resulted in a higher VO2 during the run, increased speed during the "finishing burst" and a decrease in time to completion.
Caffeine consumption prior to training has even been shown to affect testosterone and cortisol levels by elevating both. Elevated testosterone levels are associated with increased lean body mass and greater levels of peak strength. However elevated cortisol can be concerning. If this stress hormone is chronically elevated it can impact sleep and body composition.
In a study on 16 professional rugby players, ingesting either a placebo or 4mg/kg caffeine 1 hour before exercise. Athletes were classified as sleep deprived (6 hours or fewer of sleep) or non-deprived (8+ hours of sleep) and completed exercises at 65% of their 1RM in the bench, squat, and bent-over rows for a total of 4 sets per exercise. Athletes were asked to perform AMRAP (as many reps as possible) on each set. Saliva was collected before placebo/caffeine administration, before exercise and immediately after to assay for testosterone and cortisol levels. Sleep deprivation produced large decreases in total load (although caffeine ingestion moderately helped these individuals). Testosterone response to exercise increased with caffeine compared to placebo (as did cortisol response)
24 professional rugby players ingested caffeine doses of 0, 200, 400, and 800 mg one hour before resistance training and had saliva samples collected at the time of ingestion and at 15-minute intervals throughout their training session and then 15 and 30 minutes after training. Testosterone concentration increased by 15 percent during exercise, and caffeine raised this concentration in a dose-dependent manner by a further 21% at the highest dose. The 800 mg caffeine dose also increased cortisol a 52%. Caffeine produced a small decline in the testosterone: cortisol ratio of 14%
Caffeine has exercise performance-enhancing benefits in regard to reaction time, power and endurance. It can also elevate serum testosterone levels. On the opposite end, it takes a fairly significant amount of time to metabolize caffeine and it can elevate serum cortisol levels in a dose-dependent manner, which can impact anxiety and sleep. In addition to that, studies have shown there are responders and non-responders to caffeine, meaning that some individuals respond better to it than others. Caffeine can also be habituating which can reduce its effectiveness over time.
Taking this information into account it would be wise for athletes to take a few steps into consideration:
- Because of caffeine's 5 hours (on average) half-life, abstaining from evening dosages would be a wise choice.
- In studies athletes tend to benefit from the 3-6 mg/kg body weight dosage range; starting on the low end of this dosage range would be the best bet.
- It takes 30-60 minutes after ingestion to reach peak serum caffeine levels.
- Because caffeine can be habituating and it's effectiveness can wane, athletes would be wise to cycle usage by abstaining from consuming caffeine during certain phases of their training cycle.