Muscle cramps during sport: causes and clinical management

The dominant explanation for exercise-associated muscle cramps (EAMC) is dehydration and electrolyte depletion. If this were the primary mechanism, cramping would be consistent across similarly dehydrated athletes, and it is not. Some athletes cramp after 45 minutes of moderate effort. Others do not cramp in 6-hour ultras.

The dehydration model explains some cramping, particularly in very high-heat conditions with significant sweat loss. It does not explain most EAMC in controlled conditions.

The neuromuscular fatigue model (developed by Schwellnus and colleagues) proposes that EAMC originates from altered neuromuscular control at a fatigued muscle. When a muscle fatigues, the balance between excitatory signals (from muscle spindles) and inhibitory signals (from Golgi tendon organs) shifts, the muscle receives more excitatory drive and loses the inhibitory regulation that prevents sustained involuntary contraction.

This explains why: cramps typically affect the most heavily loaded muscles, cramps occur toward the end of intense or unfamiliar effort, and stretching (which activates the Golgi tendon organ and increases inhibitory signalling) provides immediate relief.

Training load specificity: muscles that cramp in races have not been adequately prepared for that load in training. Pacing: EAMC risk increases dramatically with effort intensity above what the athlete has trained at. Strength training for the muscles at highest risk, particularly the calves and hamstrings in runners, increases their fatigue resistance.

Salt supplementation (pickle juice, electrolyte tablets) has some evidence for reducing severity and duration, but it works partly through a nervous system reflex response, not solely through electrolyte replacement.

Athletes who maintain regular soft tissue therapy show lower cramping frequency in clinical observation, likely because manual work reduces baseline muscle overactivity and improves tissue quality, allowing the muscle to sustain load longer before reaching the fatigue threshold where cramping occurs.