Past about an hour of hard exercise, in heavy sweating heat, or during vomiting and diarrhea - the rest of the time, water covers it.
The ACSM position stand is specific: electrolyte-carbohydrate drinks are recommended for exercise over one hour (sodium 0.5 to 0.7 g/L aids retention and guards against hyponatremia); under an hour, evidence shows little difference from plain water. A sodium review adds that even athletes do not need elevated day-to-day sodium - kidneys regulate ordinary losses. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper .
What to do
Common questions
When do I actually need electrolytes?
Three real situations - and the gym-bag daily habit is not one of them. The American College of Sports Medicine's position is specific: adding electrolytes to fluid is recommended for exercise lasting longer than one hour, where sodium (0.5 to 0.7 grams per liter) aids fluid retention and guards against hyponatremia - while for exercise under an hour there is little evidence of any difference between an electrolyte drink and plain water. Situation two: heavy sweating in heat, where sweat sodium losses are genuinely high and variable between people. Situation three: illness - vomiting and diarrhea drain sodium and potassium fast, which is what oral rehydration solution exists for. What does not make the list: desk days, moderate workouts under an hour, and normal eating - a sodium-focused review notes there is no evidence athletes even need elevated day-to-day sodium, because kidneys regulate losses, and a normal diet replaces what ordinary exercise takes. The sports drink industry sells to hour three of a marathon and gets bought for a 40-minute jog; water handles the jog.