Caffeine is one of the most frequently consumed drugs in the world and for good reason. It has a positive effect on alertness and concentration, and can even decrease the risk of a multitude of chronic conditions, including cardiovascular and metabolic disorders.
In further support of this socially acceptable drug, caffeine has been shown to enhance exercise performance. More specifically, it has been observed that caffeine supplementation can improve aerobic endurance, muscular endurance, maximum strength, sprint performance, and high-intensity efforts. It has also been shown to decrease the rating of perceived exertion and pain during exercise.
While there are a few mechanisms that have been hypothesized to be driving the ergogenic effect of caffeine, the most widely accepted is its ability to act as an adenosine receptor antagonist. This leads to increased dopamine and noradrenaline release and ultimately promotes feelings of wakefulness and alertness.
As evidenced by the former, there are numerous benefits to be gained from ingesting caffeine. In terms of evidence-based supplements to improve athletic performance, caffeine is at the top of the list with creatine monohydrate. Considering the ability of caffeine to provide a competitive edge, there is growing interest in how to maximize the magnitude of effect derived from caffeine supplementation.
Research on caffeine has been generated to determine the best source, dose, and time of ingestion to enhance athletic performance. Trials have also been produced to elucidate whether the ergogenic effect of caffeine is reduced with habitual intake and if there is any advantage to abstaining from use for a brief period of time.
Within the sports nutrition community, it is traditionally believed that the ergogenic effect of caffeine decreases with chronic use. Furthermore, it is commonly recommended to remove caffeine from the diet in the days prior to competition in order to resensitize the body to its effects. The rationale being that this will facilitate a greater boost in performance from supplementation on game day.
The origins of this theory stem from research on rodents, which showed regular caffeine intake upregulated adenosine receptors, and as a consequence, the effect of a given dose of caffeine was blunted. These findings suggest that habitual caffeine users would need progressively higher doses over time to continue experiencing the same effects.
While studies on rodents provide useful mechanistic insight, the results cannot necessarily be extrapolated to humans. In this research, ridiculously high doses of caffeine were given (20 mg/kg). Moreover, this amount was given in a single dose, which might not mirror how most go about their daily caffeine use (e.g., multiple smaller doses throughout the day).
For these reasons, to determine whether or not the ergogenic effect of caffeine is reduced with habitual use, it’s important to look at placebo-controlled human trials that directly assessed performance outcomes.
Time Course of Caffeine Tolerance
In a double-blind, placebo-controlled, randomized, and cross-over experimental design, 11 healthy active subjects, who were light caffeine consumers (< 50 mg/day), took part in two identical protocols. In one protocol, participants ingested 3 mg/kg body mass of caffeine each day for 20 consecutive days. In the other protocol, they ingested a placebo for 20 days.
Three times per week during each intervention period, participants performed the same exercise regimen composed of a maximal graded exercise test on a cycle ergometer to volitional fatigue and an adapted version of the Wingate test (15-second all out sprint).
The results displayed that in comparison to the placebo, caffeine increased peak cycling power during the graded exercise test throughout the duration of the trial. The effect size of caffeine intake was large on days 1 and 4 and decreased to moderate afterward. A similar trend was observed for VO₂ max.
For the Wingate test, daily intake of caffeine increased peak power on days 1,4,15, and 18. The effect size of caffeine intake was large on days 1 and 4 and was reduced to moderate/small afterward.
In this trial, the ergogenic effect of caffeine peaked on day 1 of ingestion and decreased afterward. In light of this fact, caffeine supplementation did continue to exert small to moderate improvements in performance throughout the duration of the study.
In another study, 18 healthy, recreationally active men, who habitually consumed < 75 mg of caffeine per day, were randomly assigned to receive either daily caffeine supplementation (1.5 mg/kg body mass per day for seven days, followed by 3 mg/kg body mass per day) or placebo for 28 days.
Participants performed an exercise test on three occasions. The test featured 60 minutes of cycling at an intensity equivalent to 60% of VO₂ max, followed by a 2-3 minute delay. Performance was then assessed as the maximum amount of external work that could be completed in 30 minutes.
At baseline, each subject completed the exercise test after ingesting 3 mg/kg body mass of caffeine and placebo. Participants were then randomized to the caffeine or placebo group for 28 days and retested. During the retest, all participants consumed 3 mg/kg body mass of caffeine.
Similar to the previous trial, the results of this experiment displayed that after 28 days of regular caffeine use, supplementation still produced an improvement in performance, albeit less than it did at the initial test.
Together, these studies suggest that regular caffeine use can reduce its ergogenic effect, but not eliminate it. In further analysis of this sentiment, there are some important points to consider, such as the dose of caffeine utilized.
In both of these trials, the dose of caffeine remained stagnant throughout the intervention. Moreso, the dose ingested prior to the exercise tests was the same as the daily dose.
What would happen if the dose was increased prior to the test? Would we see the same effect size observed at the initial test (i.e., before high habitual caffeine use)? Also, would we see less attenuation of the ergogenic effect if the dose was periodized over the course of the intervention?
We will return to some of these ideas later on in the article, but first, I would like to explore some other research to tease out the answer to our primary question: does habitual caffeine use reduce its ergogenic effect?
To accomplish this task, let’s take a look at a few trials that featured both high and low habitual caffeine users, and then assessed whether users with high daily intake, experienced less of an ergogenic effect than users with low daily intake.
The Effect of Caffeine in Low Versus High Habitual Users
In a double-blind, counterbalanced, crossover study, titled “Dispelling the myth that habitual caffeine consumption influences the performance response to acute caffeine supplementation,” 40 recreationally trained male cyclists underwent three experimental trials: caffeine supplementation (6 mg/kg body mass of caffeine), placebo supplementation, and no supplement (CON).
The exercise component of each experimental trial featured a cycling time trial test where participants were required to perform a set amount of work in the shortest time possible.
To test the influence of caffeine intake on the exercise response to acute caffeine supplementation, participants were allocated into tertiles based on their dietary intake of caffeine. Low consumers were classified by an intake of 58 ± 29 mg/day, moderate consumers were classified by an intake of 143 ± 25 mg/day, and high consumers were classified by an intake of 351 ± 139 mg/day.
It was reported (can you guess based on the title?) that time trial performance was significantly improved with caffeine compared to placebo (+2.4%) and control (+3.3%). Further analysis revealed that the level of habitual caffeine ingestion was not associated with the magnitude of improvement in cycling time trial performance following acute caffeine supplementation.
When interpreting the results of this trial, it’s critical to consider the dose of caffeine supplementation. When you look at the average body weight of the subjects in each group (72.08, 74.95, and 76.05 kg, respectively), and multiply that by the amount of caffeine given, the average dose was ~430-455 mg, which far exceeds the intake of the vast majority of subjects.
With that being said, the findings of this trial indicate that caffeine habituation can potentially be offset by utilizing a higher dose.
In another study featuring a within-subject design, 18 active college students completed a 12 x 30-meter sprint test to test the ergogenic effect of caffeine. The subjects were classified as caffeine naive (~27.66 mg/day) and habitual users (~314.80 mg/day).
Subjects were randomized to receive 6 mg/kg body mass of caffeine mixed in a sports drink or a placebo (plain sports drink) one hour prior to testing. The dose of supplementation equated to 425.57 mg on average and this was above all of the participants’ normal caffeine consumption.
At the end of the trial, it was found that caffeine supplementation led to faster mean sprint times, though only sprints three and five out of 12 reached significance. In addition, no significant difference was found in the fastest individual sprint times with caffeine ingestion between caffeine naive and habitual consumers.
Moving on to a brand new trial that utilized a randomized, double-blind, counterbalanced design, participants were tested on four occasions and stratified based on their habitual caffeine use.
Participants with a daily intake of <165 mg, were classified as low users, and participants with an intake > 165 mg/day were classified as moderate-high users.
The first two sessions served as familiarization sessions, while sessions three and four were experimental sessions consisting of caffeine and placebo supplementation. Caffeine supplementation (3 mg/kg) was provided 60 minutes before the start of exercise.
The exercise sessions were as follows: movement velocity and power in the bench press were assessed with loads of 25%, 50%, 75%, and 90%. At each load, participants performed two sets of one repetition. This was followed by a muscular endurance test that involved a performance of one set to momentary muscular failure in the bench press with 85% 1RM. After the muscular endurance test, subjects performed three countermovement jumps. Lastly, subjects completed a Wingate test (30-second cycling sprint).
In the end, it was found that the effects of caffeine on various modes of exercise were not significantly different between groups.
Similar to the previously discussed studies, the amount of caffeine given prior to the exercise sessions was equal to or greater than the amount of caffeine taken habitually for 21 out of the 24 participants.
In combination, these three trials suggest that any potential attenuation in the ergogenic effect of caffeine from habitual use can be offset by ingesting a greater than usual dose.
When assessing the literature as a whole, it’s difficult to come to any strong conclusion on the topic of whether high habitual caffeine users experience less of an ergogenic effect from caffeine supplementation than low habitual users. The reason for this is heterogeneity between studies.
As evidenced by the above, there is wide variation between trials in the exercise intervention, the dietary questionnaire used to assess habitual caffeine intake, and the criteria used to classify subjects as high or low habitual caffeine users.
While I don’t think we can say for sure whether or not high habitual caffeine users experience less of an ergogenic effect from caffeine supplementation, it does seem likely, and I would venture to say that most anecdotal evidence would agree.
Transitioning to what we can confidently conclude from the available research, high habitual caffeine use does not completely eliminate its ergogenic effect. Also, it seems clear that any possible reduction in the ergogenic effect of caffeine from habitual use can be offset by consuming a greater than usual dose.
With those primary points out of the way, we can move on to our last area of interest, that is, does abstaining from caffeine use resensitize the individual to its physiological effects?
Resensitizing to Caffeine
In an older experiment conducted by Van Soeren and Graham, six recreational male athletes with a very high habitual caffeine intake (761 ± 11.8 mg/day) performed seven trials with a minimum of ten days between trials.
On the day of the exercise trial, subjects ingested either placebo or 6 mg/kg body mass of caffeine one hour before cycle ergometry to exhaustion at 80-85% of maximum oxygen uptake.
The first two trials were completed without any withdrawal to caffeine and subjects were assigned randomly to either placebo or caffeine. Subsequent exercise tests were conducted after periods of either a two or four day withdrawal from caffeine. In the last experiment, all subjects participated in a placebo-repeat trial without any period of withdrawal from caffeine.
It was found that time to exhaustion was longer in all caffeine trials compared to placebo, but no significant differences existed between withdrawal periods, though it did appear that abstaining from caffeine use slightly boosted its effects.
The results also showed that all of the subjects reported withdrawal symptoms from abstaining from caffeine. These included severe headaches, fatigue, and lethargy.
In a more recent study, 12 well-trained cyclists and triathletes with a habitual caffeine intake of 240 ± 162 mg/day completed four experimental trials. The treatment conditions involved ingestion of placebo or caffeine (3 mg/kg body mass) for four days followed by an acute administration of placebo or caffeine on trial day.
This translated to placebo for four days plus placebo 90 min prior to the exercise test, placebo for four days plus caffeine prior to the exercise test, caffeine for four days plus placebo prior to the exercise test, and caffeine for four days plus caffeine prior to the exercise test.
Each exercise test was separated by at least seven days and involved a cycling time trial that required participants to complete a set amount of work as fast as possible, equivalent to one hour of cycling at 75% peak power output.
It was found that there was no difference in time for caffeine plus placebo and placebo plus placebo. The same was observed for placebo plus caffeine and caffeine plus caffeine.
To add, 20 of the 24 trials were faster when caffeine was administered on trial day, regardless of the pre-trial treatment condition. Overall, the researchers found that a four day withdrawal period had no impact on the ergogenic effect of caffeine
Similar to the previous study, a multitude of withdrawal symptoms were reported by all participants except one. These included headaches, fatigue, and a lack of focus and motivation.
Together, the available evidence suggests that abstaining from caffeine intake for a brief period of time does not enhance the ergogenic effect of caffeine, but it does induce a variety of symptoms that negatively impact the subjects’ well-being.
While we can’t rule out that four days might be an insufficient amount of time to truly resensitize to the ergogenic effect of caffeine, the current research reports that short-term withdrawal from caffeine does not significantly enhance its ergogenic effect. Rather, it merely reverses the side effects associated with withdrawal.
Is it necessary to cycle caffeine? Perhaps not, but it may be worthwhile to maximize its ergogenic effect.
It appears that high habitual caffeine use can reduce its ergogenic effect, but not eliminate it. In addition, ingesting a larger than usual dose can counter this attenuation. Lastly, removing caffeine from the diet for a few days does not seem to resensitize the individual to its effects, but it does induce some pretty nasty withdrawal symptoms.
For these reasons, I think it may be useful to apply some form of periodization to caffeine ingestion to potentially augment its effects when they’re needed the most. The sports nutrition literature points toward 3-6 mg/kg body mass of caffeine as a sufficient dose to provide an ergogenic effect.
With that information in mind, it may be wise to limit caffeine intake to ~ 3 mg/kg on days with easy to moderate training sessions, utilize the upper end of the aforementioned range (if needed) for hard training sessions and competition, and keep it to a minimum or remove it entirely on rest days.