Salt your food. Salt your water. Salt your life on long runs.
Sodium Needs
500–1000mg per hour during exercise in heat. Individual sweat rates vary widely.
Signs of Imbalance
Headache, nausea, muscle cramps, and confusion signal hyponatremia or dehydration.
Testing
Weigh yourself before and after a 60-minute session. Each pound lost equals ~16 oz fluid deficit.