A new study suggests that drinking caffeine before exercising in hot weather may help improve endurance and make workouts feel less difficult.
Researchers recruited 17 trained participants for a randomized, double-blind study. 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 (3 mg per kilogram of body weight), or a higher dose of caffeine (6 mg per kilogram of body weight). For a 150-pound person, 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.
Higher caffeine doses showed better results
Both caffeine doses helped, but the higher dose stood out. Endurance time improved significantly, fully eliminating the performance decline caused by the heat. Participants who took caffeine 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. Both caffeine groups showed improved VO2 peak, a key marker of aerobic capacity, with stronger results in the high-dose group.
Caffeine appeared to help most with the subjective side of exercise, or how exhausting it felt. This effect is tied to caffeine’s ability to block adenosine receptors in the brain, reducing the perception of fatigue and boosting motivation.
Considerations before using caffeine for hot workouts
The results suggest caffeine, especially at 6 mg per kilogram, can be a useful tool for training or competing in hot conditions. But the study authors advise caution. People who are sensitive to caffeine should start with a lower dose of 3 mg per kilogram or less. Caffeine should be taken about 60 minutes before exercise to allow time for absorption. Staying hydrated is important, as caffeine is mildly diuretic and heat can compound dehydration. Responses to caffeine can vary based on genetics, training status, and gender.
The study provides evidence that caffeine, when used thoughtfully and in the right dose, can help offset the typical drop in performance, improve breathing, and make tough workouts feel more manageable.
