This Common Ingredient Can Make Your Hot Workouts Feel Way Easier
If you’ve ever cut a workout short because the heat was too much, you’re not alone. Exercising in the summer sun can feel like moving through molasses—your heart rate spikes faster, your breath gets shallow, and even light activity can drain your energy in minutes.
But a new study suggests a surprisingly simple tool might help you power through: caffeine. Specifically, the right dose of caffeine taken before a workout in the heat could be the difference between quitting early and pushing through strong.
This research dives into how caffeine affects endurance, lung function, and perceived fatigue in hot conditions. And the findings could shift how we think about pre-workout fueling, especially if you train outdoors or in warm environments.
How caffeine affects performance in the heat
To figure out whether caffeine can help counteract the usual performance dip that comes with hot-weather exercise, researchers recruited 17 trained participants for a randomized, double-blind study. Each person completed four different workouts: one in a comfortable room (around 76°F) and three in a hot environment (about 92°F).
Before the hot workouts, participants took either:
- A placebo (no caffeine)
- A moderate dose of caffeine (3 mg/kg body weight)
- A higher dose of caffeine (6 mg/kg body weight)
For reference, a 150-pound person would get about 200 mg of caffeine at the lower dose (roughly two strong cups of coffee) and 400 mg at the higher dose (closer to four or five strong cups). While some people may mesh well with this amount of caffeine pre-workout, not everyone can (or should) handle doses that high.
During the workouts, researchers tracked several key performance markers: endurance time, lung function, aerobic capacity (VO2 peak), and how hard the workout felt (known as “perceived exertion”).
Higher caffeine = better endurance & easier breathing
So what did they find? Both caffeine doses helped, but the higher dose stood out in several important ways:
- Endurance time improved significantly: The higher dose fully eliminated the performance decline caused by the heat, while the moderate dose helped slightly.
- Breathing became easier: Participants who took caffeine had better pulmonary ventilation, meaning they could take in more oxygen and move air through their lungs more efficiently.
- The workout felt easier: Only the higher caffeine dose significantly reduced how hard the exercise felt, even as intensity increased.
- VO2 peak increased: This is a key marker of aerobic capacity, and higher VO2 typically means you can go harder for longer. Both caffeine groups improved, with stronger results in the high-dose group.
Interestingly, caffeine seemed to help the most with the subjective side of exercise (aka how exhausting it felt). This is a known effect of caffeine, tied to its ability to block adenosine receptors in the brain.
By doing this, caffeine reduces the brain’s perception of fatigue and boosts motivation, basically making your brain think the workout is less taxing than it actually is.
So, should you take caffeine before every hot-weather workout?
The results suggest that caffeine, especially at 6 mg/kg, can be a powerful tool if you’re training or competing in hot conditions. But that doesn’t mean everyone should start doubling their cold brew.
Here’s what to keep in mind:
- Start small: If you’re caffeine-sensitive, try a lower dose first (3 mg/kg or less). For many people, even a cup of coffee can provide noticeable benefits.
- Time it right: Most studies (including this one) administered caffeine about 60 minutes before exercise. That gives your body time to absorb and use it.
- Stay hydrated: Caffeine is mildly diuretic, and heat can compound dehydration. Make sure you're drinking enough water, especially during longer sessions.
- Listen to your body: While caffeine helped most participants, responses can vary based on genetics, training status, and even gender.
The takeaway
Working out in the heat can be brutal, but it doesn't have to be a struggle. This study offers strong 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.
If you're already reaching for coffee before a morning run, you're not just fueling motivation; you could be giving your body a legitimate performance edge. And if you’ve been dragging through hot workouts, this research might give you a smart (and science-backed) reason to experiment with a bit more.