Exercising in high heat can feel draining, but a new study suggests that drinking caffeine before a workout may help people push through the discomfort. Researchers recruited 17 trained participants for a randomized, double-blind study to test how caffeine affects performance in hot conditions.
Each person completed four workouts: one in a comfortable room at about 76 degrees Fahrenheit and three in a hot environment at about 92 degrees Fahrenheit. Before the hot workouts, participants took either a placebo, a moderate dose of caffeine at 3 milligrams per kilogram of body weight, or a higher dose at 6 milligrams per kilogram of body weight.
For a person weighing 150 pounds, the lower dose equals about 200 milligrams of caffeine, roughly two strong cups of coffee. The higher dose equals about 400 milligrams, closer to four or five strong cups. Researchers tracked endurance time, lung function, aerobic capacity, and how hard the workout felt.
The higher dose of caffeine produced the strongest results. Endurance time improved significantly, with the high dose fully canceling out the performance decline caused by heat. Participants who took caffeine also had better pulmonary ventilation, meaning they could take in more oxygen and move air through their lungs more efficiently.
Only the higher dose reduced how hard the exercise felt, even as intensity increased. Both caffeine groups showed improvement in VO2 peak, a key marker of aerobic capacity that indicates how long someone can sustain effort. The high-dose group had stronger results in this area.
Caffeine works by blocking adenosine receptors in the brain. This reduces the brain’s perception of fatigue and boosts motivation, making the workout feel less taxing than it actually is. The effect was most noticeable in how participants rated their level of exertion.
The study does not suggest everyone should take high doses before every workout. People who are sensitive to caffeine should start with a lower dose of 3 milligrams per kilogram or less. Even one cup of coffee can provide benefits for many people.
Timing matters. Most studies, including this one, gave caffeine about 60 minutes before exercise. This allows the body time to absorb and use it. Staying hydrated is also important, as caffeine is mildly diuretic and heat can compound dehydration.
Responses to caffeine can vary based on genetics, training status, and gender. While most participants benefited, individual results may differ. The study offers evidence that caffeine can help offset the typical drop in performance in hot conditions, improve breathing, and make tough workouts feel more manageable.
Related context on heat and exercise
Exercising in summer heat can cause heart rate to spike faster and breath to become shallow. Even light activity can drain energy in minutes. The body works harder to cool itself, which diverts blood flow away from muscles and can reduce endurance.
Proper hydration and timing of food and drink intake are common strategies for managing heat during workouts. Caffeine joins that list as a potential tool, but it should be used thoughtfully based on individual tolerance and needs.
