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How Hydration Affects Exercise Performance
Hydration status has a measurable, well-documented effect on exercise performance, and even small fluid deficits can noticeably impact how a workout feels and performs.
The effect on endurance
Fluid loss equal to just 2% of body weight — a little over 1kg (2 lbs) for a 70kg person — has been shown in research to reduce endurance performance, increase perceived effort, and raise heart rate at a given pace compared to being well hydrated.
The effect on strength and power
Strength and power output are somewhat more resilient to mild dehydration than endurance performance, but more significant fluid loss still impairs focus, coordination, and overall training quality.
Hydrating before, during, and after
Drinking fluids in the hours before exercise, sipping regularly during longer sessions (especially over an hour), and rehydrating afterward based on how much weight was lost through sweat all support better performance and faster recovery.
A practical approach
Rather than a rigid formula, checking urine color before a workout, drinking to thirst during shorter sessions, and being more deliberate about fluids and electrolytes during long or hot-weather training covers most people's needs.
Put it into practice
Try the Water Intake Calculator →
Estimate your daily water intake target.
Frequently Asked Questions
Yes — drinking excessive amounts during very long endurance events without adequate sodium can lead to a dangerous condition called hyponatremia, so more isn't always better during extended exercise.
Medical disclaimer
This article is for general informational and educational purposes only and isn’t a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your specific health situation.
