How much caffeine should you take, and when?
The most effective dose for endurance is 3–6 mg per kilogram of body weight, taken about 60 minutes before exercise. A 2021 position stand from the International Society of Sports Nutrition (ISSN) concluded that doses in this range consistently improve aerobic endurance, with benefits also seen at doses as low as 2 mg/kg [3]. For a 70 kg (154 lb) person, that means 210–420 mg of caffeine—roughly 2–4 cups of coffee.
Timing matters: most research uses a 60-minute pre-exercise window, but caffeine chewing gum may work faster [3]. A 2022 survey of endurance athletes found that about half take caffeine within 30 minutes of training or races, and recreational athletes often use lower doses (1.6 mg/kg before training) than the research-tested amounts [5]. This suggests many athletes could benefit from slightly higher, properly timed doses.
Why does caffeine work better for some people than others?
Your genes play a big role. A key gene called CYP1A2 controls how fast you metabolize caffeine. A 2019 study of 101 competitive male cyclists found that those with the 'AA' genotype (fast metabolizers) improved their 10-km cycling time by 6.8% with 4 mg/kg of caffeine, while those with the 'CC' genotype (slow metabolizers) actually got 13.7% slower on the same dose [9]. A 2022 study confirmed this pattern and added that another gene (HTR2A) also influences the effect: among fast metabolizers, those with the CC version of HTR2A improved by 2.4 minutes on a 10-km time trial, while those with the TT version improved only 0.7 minutes [4].
This means that for about 40–50% of the population (the fast metabolizers), caffeine is a reliable performance booster. For slow metabolizers, high doses can backfire. A 2021 study on muscle strength found that slow metabolizers (CC genotype) lost 12.8% of handgrip strength after 4 mg/kg of caffeine [8]. So if you feel jittery or perform worse after coffee, your genes might be the reason.
Does regular coffee drinking reduce the benefit?
Yes, habitual caffeine use can blunt the performance boost. A 2025 study of 80 men found that those who consumed caffeine daily for 8 weeks had a smaller improvement in a 3-km run and Wingate power test compared to non-habitual users [2]. However, the study also found that taking a higher dose (6 mg/kg instead of 3 mg/kg) or taking a short break from caffeine (a few days) restored the ergogenic effect [2].
On the other hand, a 2026 study of 21 collegiate baseball players found that 3 mg/kg of caffeine did not improve strength or endurance at all, regardless of whether they were habitual users or not [6]. And a 2020 study on athletes who consumed about 411 mg of caffeine daily found that very high doses (9 and 11 mg/kg) also failed to improve bench press performance [7]. So while habituation can reduce the effect, the optimal strategy may be to cycle caffeine use or increase the dose slightly, but not to extreme levels.
Sources used in this answer
Caffeine Increases Exercise Performance, Maximal Oxygen Uptake, and Oxygen Deficit in Elite Male Endurance Athletes
Caffeine (4.5 mg/kg) increased time to exhaustion by 5.5% and maximal oxygen uptake (VO2max) by 1.2% in elite male endurance athletes.
Habitual Caffeine Consumption and Training Status Affect the Ergogenicity of Acute Caffeine Intake on Exercise Performance
Habitual caffeine consumption reduced the ergogenic effect of caffeine on 3-km run time and Wingate power; a higher dose (6 mg/kg) or short-term withdrawal restored it.
International society of sports nutrition position stand: caffeine and exercise performance
The ISSN position states that 3–6 mg/kg caffeine improves aerobic endurance, muscular endurance, and cognitive function, with benefits also at 2 mg/kg.
Effect of Caffeine on Endurance Performance in Athletes May Depend on HTR2A and CYP1A2 Genotypes.
Among CYP1A2 fast metabolizers, those with the HTR2A CC genotype improved 10-km cycling time by 2.4 minutes with 4 mg/kg caffeine, versus 0.7 minutes for TT.
Caffeine Supplementation Strategies Among Endurance Athletes
A survey of 254 endurance athletes found that 24% used caffeine supplements; recreational athletes used lower doses (1.6 mg/kg) than research protocols.
The Effect of Habitual Caffeine Use on Strength, Power, and Muscular Endurance Performance in Collegiate Athletes.
Caffeine (3 mg/kg) did not improve strength, power, or muscular endurance in 21 collegiate baseball players, regardless of habitual use.
The Effects of High Doses of Caffeine on Maximal Strength and Muscular Endurance in Athletes Habituated to Caffeine.
High doses of caffeine (9 and 11 mg/kg) did not improve bench press strength or endurance in athletes habituated to caffeine.
CYP1A2 Genotype Modifies the Effects of Caffeine Compared With Placebo on Muscle Strength in Competitive Male Athletes
Caffeine (4 mg/kg) decreased handgrip strength by 12.8% in individuals with the CYP1A2 CC genotype, but had no effect in AA or AC genotypes.
Caffeine, CYP1A2 Genotype, and Endurance Performance in Athletes.
Caffeine (4 mg/kg) improved 10-km cycling time by 6.8% in CYP1A2 AA fast metabolizers but worsened it by 13.7% in CC slow metabolizers.