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Drinking Water During Exercise Has An Unexpected Limitation
You’re halfway through a long run, the sun is beating down, and you reach for your water bottle.
You’ve always heard that staying hydrated helps you perform your best. Water replaces fluid lost through sweat and helps regulate body temperature, but does drinking more actually help you run faster or exercise longer?
A systematic review and meta-analysis of 24 studies1 examined how different hydration strategies affect endurance exercise, including whether following a drinking schedule works better than drinking when you're thirsty.
About the review
The review analyzed 24 randomized trials involving 225 participants in total.
The participants were adults who exercised continuously for at least 60 minutes. Rather than testing all three hydration approaches in one large group, the review combined results from separate trials that compared different strategies.
Some trials compared drinking fluids with drinking little or none, while others compared following a drinking schedule with drinking to thirst or consuming different amounts of fluid.
The trials measured exercise performance and physical responses, including heart rate and core temperature.
Drinking water didn't necessarily improve performance
Compared with drinking little or nothing, drinking during exercise led to no clear improvement in how quickly participants finished a time trial or how much work they completed in a set time.
Some studies suggested drinking might help people exercise longer before exhaustion, but the evidence was too uncertain to confirm this.
The physical effects were clearer. People who drank during exercise tended to have lower heart rates and core temperatures than those who drank little or nothing.
In separate comparisons, people who followed planned hydration schedules lost less body weight during exercise than those who drank when thirsty. However, the overall evidence is very uncertain, so these results aren't definitive.
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Why a cooler body doesn't mean a faster finish
Drinking during exercise may help your body manage heat and physical strain without necessarily making you faster.
A lower heart rate or core temperature doesn't guarantee better performance, which also depends on fitness, pacing, and workout conditions.
So, does everyone need to follow a strict drinking schedule? Not necessarily. For shorter workouts in moderate conditions, drinking to thirst may be enough for many people.
Longer sessions and hot, humid weather bring greater sweat losses, making hydration more important. The review doesn't establish one ideal strategy for everyone, but it suggests that drinking on a schedule doesn't automatically improve performance compared with drinking when thirsty.
How to hydrate without overdoing it
Rather than chasing a specific ounces-per-hour target, consider how long you're exercising, the weather, how much you sweat, and how comfortably you tolerate fluids.
- Adjust for conditions: A long summer run generally calls for more attention to hydration than a short workout in a cool gym.
- Pay attention to sweat loss: Longer sessions and heavier sweating increase the amount of fluid you may need to replace.
- Avoid forcing excess water: Drinking more than your body can handle can dilute sodium in your blood, causing a potentially dangerous condition called exercise-associated hyponatremia.
During prolonged exercise with substantial sweat loss, electrolytes, particularly sodium, may also be useful. Learn more about when you might need electrolytes instead of water.
The takeaway
Drinking during exercise can help your body regulate temperature and heart rate, but that doesn't guarantee a faster finish.
Match your hydration to your workout, the weather, and your sweat losses instead of assuming more water always means better performance.