Muscle cramps, and the remedy that failed

Cramp divides into two conditions that share a name and not much else: exercise-associated cramp, which happens during or after exertion, and nocturnal cramp, which happens in older adults at night, often with stretching. They have different evidence and different handling, and confusing them produces a well-sourced wrong answer.

Nocturnal cramp in older adults: magnesium does not work. This is the finding that matters most on this page. A Cochrane review concluded that magnesium was unlikely to provide meaningful prophylaxis in older adults, and a randomised trial found magnesium indistinguishable from placebo with a p-value around 0.93. The folk expectation — that night cramps are a magnesium deficiency — is not supported by the trials. A failed remedy recorded as failed is the point of this page, because otherwise magnesium is recommended again on the next pass with the same confidence.

What did work in the same trial space: compression. In the trial where magnesium did nothing, compression stockings reduced cramps by a meaningful amount per week at a real p-value. It is unglamorous and it is what the data supports.

Exercise-associated cramp is a different mechanism. The evidence points to neuromuscular fatigue and altered spinal reflex control rather than to electrolyte depletion in most cases, which fits the observation that cramping athletes usually have normal electrolytes. The famous exception is the pickle-juice trial: pickle juice reduced cramp duration in about a minute, which is far too fast for absorption — it rules out mineral delivery and implies the acid is triggering a reflex in the mouth and throat. Ask how fast an effect is claimed; faster than absorption is a different mechanism.

What genuinely helps, in order. Stop the activity and stretch the affected muscle; for night cramps, stand and put weight on the leg. Compression stockings for nocturnal cramp. Adequate conditioning and progressive loading for exercise-associated cramp. Hydration and salt for prolonged hot exercise, which is a real electrolyte scenario even if it is not the common one. Quinine works and must not be used — it causes thrombocytopenia, haemolytic-uraemic syndrome and renal failure, and its approval for cramp was withdrawn.

A test rather than a belief. Where evidence is weak in both directions, do a fixed six-week tally: cramps per week, at a stable starting point, with one intervention at a time.