Thirst is not perceived until loss of 2% body weight through sweating. But 2% fluid loss impairs performance! For that reason, we should drink with a plan rather than drink to thirst
Calculate your 2%
cramps, heat exhaustion, heatstroke No such thing as adaptation to dehydration.

Cardiovascular Psychological factors Respiratory system Central nervous system Skeletal muscle Other factors

Ambient temperature, rH, wind velocity, and solar radiation are sources of environmental heat stress. Sweat must evaporate to exert a cooling effect.

Acclimation and euhydration Exercise training: ^ blood volume ^ skin blood flow ^ size of sweat glands ^ sweat rate earlier onset of sweating

Sweat rates vary 0.5to 3 L/h during strenuous exercise in the heat. Collect regularly and in a variety of conditions.

Make drinks taste better ^ thirst ^ hydration Maintain fluid balance blood [sodium] body sodium Retains fluid Helps fluid absorption

Aim for euhydration 6-8 mL of fluid per kg of body weight ~2 h before exercise
Calculate!
Water with salty snack or CHO-electrolyte

Start drinking early Opportunities Availability Easy to ingest Doesn’t interrupt flow Cold or icy CHO + electrolytes for > 1h Ad libitum intake during exercise in the heat results in incomplete replacement of body-water losses

500-700 mg/L of sodium for exercise >1h 1.5 L per kg of weight loss to achieve euhydration within 6 h

Symptoms similar to dehydration Drink less than you sweat Should NOT gain weight