What causes muscle cramps?

The familiar explanation is dehydration and electrolyte depletion, and it is repeated so consistently that most people take it as established. The trial evidence is weaker than that suggests: studies comparing athletes who cramp against those who do not have generally found no reliable difference in hydration status or blood electrolyte levels, and cramps occur frequently in people who are neither dehydrated nor depleted. The leading current explanation is altered neuromuscular control, in which fatigue increases excitatory signaling from muscle spindles while decreasing inhibitory signaling from Golgi tendon organs, leaving the motor neuron firing when it should be quiet.

That model fits observations the older one struggles with. Cramps tend to occur in muscles that are shortened and fatigued, often late in exercise or at night, and they respond immediately to stretching, which activates the inhibitory reflex. It also explains why pickle juice appears to work faster than any electrolyte could be absorbed, with research suggesting the effect comes from receptors in the mouth and throat triggering a reflex that dampens motor neuron firing rather than from replacing anything.

Practical guidance follows the evidence: stretch and gently massage the affected muscle, which usually resolves an acute cramp within seconds to minutes, and address fatigue through conditioning and pacing rather than relying on supplements. Adequate hydration and nutrition still matter for performance and health broadly, so this is not an argument against them. Nocturnal leg cramps are common in older adults and pregnancy and are usually benign. Worth seeing a doctor if cramps are frequent and severe, occur alongside muscle weakness or wasting, or begin after starting a medication, since diuretics, statins, and several other drug classes are associated with them, and since underlying conditions including thyroid disorders, nerve compression, and circulation problems can present this way.