A new study suggests that caffeine taken before exercise in hot conditions can help improve endurance and make the workout feel easier.
Researchers recruited 17 trained participants for a randomized, double-blind study. Each person completed four different workouts. One workout took place in a comfortable room at about 76 degrees Fahrenheit. The other three workouts were in a hot environment at about 92 degrees Fahrenheit.
Before the hot workouts, participants took one of three things: a placebo with no caffeine, a moderate dose of caffeine at 3 mg per kilogram of body weight, or a higher dose of caffeine at 6 mg per kilogram of body weight. For a person weighing 150 pounds, the lower dose equals about 200 mg of caffeine, roughly two strong cups of coffee. The higher dose equals about 400 mg, closer to four or five strong cups.
During the workouts, researchers tracked endurance time, lung function, aerobic capacity, and how hard the workout felt to each person.
The results showed that both caffeine doses helped, but the higher dose had stronger effects. Endurance time improved significantly with the higher dose. Participants who took caffeine had better pulmonary ventilation, meaning they could take in more oxygen. The higher dose also reduced how hard the exercise felt. Both caffeine groups showed improved aerobic capacity, with stronger results in the high-dose group.
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 study suggests that caffeine at 6 mg per kilogram can be a useful tool for training or competing in hot conditions. However, the researchers advise starting with a lower dose for people who are sensitive to caffeine. Even one cup of coffee can provide benefits for many people.
Timing also matters. Most studies, including this one, gave caffeine about 60 minutes before exercise. Staying hydrated is important because caffeine is mildly diuretic, and heat can worsen dehydration. Responses to caffeine can vary based on genetics, training status, and gender.
The findings indicate that caffeine can help offset the typical drop in performance in hot weather, improve breathing, and make tough workouts feel more manageable. People who already drink coffee before a morning run may be getting a legitimate performance edge from their habit.
