What Causes Exercise-Associated Muscle Cramps?

The Long-Standing Explanation

For decades, exercise-associated muscle cramps were almost universally attributed to dehydration and electrolyte depletion — sodium, potassium, magnesium and calcium imbalances disrupting normal muscle function during prolonged exertion.

An Explanation the Evidence Doesn't Fully Support

A detailed review of the evidence found this dehydration/electrolyte theory poorly supported by the available research — cramping athletes often show blood electrolyte and hydration levels no different from non-cramping athletes in the same event, and cramps frequently occur in specific, localised muscles rather than the generalised pattern that systemic electrolyte depletion would be expected to produce (Schwellnus, 2009).

A More Supported Alternative: Altered Neuromuscular Control

The same review found stronger support for an "altered neuromuscular control" theory, proposing that cramps arise from a localised imbalance between excitatory signals from muscle spindles and inhibitory signals from Golgi tendon organs, triggered by muscle fatigue — essentially a localised failure of the reflex circuit that normally regulates muscle contraction, rather than a whole-body chemical imbalance.