Electrolytes are minerals that carry an electrical charge in body fluids, enabling nerve signalling, muscle contraction, and fluid balance. The primary electrolytes for athletic performance are sodium, potassium, magnesium, calcium, and chloride. Sweat loss depletes these minerals, and significant depletion impairs performance and, at extremes, creates medical emergencies.
Sodium is the primary sweat electrolyte and the most important to replace during exercise. It maintains blood plasma volume, helps retain fluid in the bloodstream, and prevents hyponatraemia (dangerously low blood sodium from drinking too much plain water without replacing sodium). Sweat rates and sodium concentrations vary significantly between individuals - "salty sweaters" (those with visible white residue on skin after exercise) need considerably more sodium than average. Potassium works with sodium to maintain cellular fluid balance and is crucial for proper muscle contraction and preventing cramps. Dietary sources: bananas, potatoes, spinach, avocado.
For exercise under 60-90 minutes in moderate conditions, water alone is sufficient for most athletes. Beyond 90 minutes, particularly in heat: use electrolyte drinks, tablets (Nuun, Hydralyte), or add a small pinch of salt to water with a squeeze of lemon. Sports drinks like Gatorade provide electrolytes but also substantial sugar (appropriate for endurance athletes needing carbohydrates, but excessive for shorter duration activities). Low-sugar electrolyte options are better for strength athletes who don't require carbohydrate supplementation during training.