Electrolyte

Magnesium

If sodium and potassium fire the muscle, magnesium lets it let go. It's required for muscles to relax after contracting — which is why low magnesium is linked with cramping and twitching. It's also involved in how your body produces energy at the cellular level, so it plays a role in endurance, not just cramp prevention. Sweat pulls magnesium out slowly but steadily, and it's one of the most common shortfalls in athletes' diets.