Cramps : Muscle cramps during racing

Involuntary, painful muscle contractions that often occur late in a race, linked to fatigue and dehydration.

Race cramps have two main causes: neuromuscular fatigue (muscles pushed beyond their capacity) and electrolyte deficit (sodium, potassium, magnesium) worsened by sweat losses. In Ironman, they typically strike in the last two-thirds of the marathon. Prevention involves adequate training at target volume, a rigorous fuelling strategy, and heat acclimatisation if racing in hot conditions.

Source Schwellnus M.P. et al., 2019 : Cause of Exercise Associated Muscle Cramps - Altered Neuromuscular Control, Dehydration or Electrolyte Depletion (Br J Sports Med)