Research
Energy balance
Dehydration exceeding 2% of body mass impairs aerobic performance in warm-hot environments, contradicting the 'drink to thirst' approach for severe events.
Start your event well-hydrated (drink 6ml/kg every 2-3 hours before). During the event, try to replace sweat losses. After the event, drink fluids with meals and electrolytes to recover fully. Don't rely solely on thirst if you are sweating heavily.
GoodQualifiesHIGH confidence
Numerous studies report that dehydration impairs aerobic performance in the condition that if exercise is performed in warm-hot environments and that body water deficits exceed at least ~2% of body mass.
Why this rating
Consensus statement acknowledging a polarized debate but citing numerous studies.
Source
Consensus recommendations on training and competing in the heat
Sébastien Racinais et al. · British Journal of Sports Medicine · 2015
DOI 10.1136/bjsports-2015-094915
clinical_guidelineCited 330×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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