From the Guidelines
Exercise-associated muscle cramps (EAMC) are primarily caused by heat-induced symptoms, dehydration, and electrolyte imbalances, as evidenced by the American Heart Association guidelines 1. When engaging in vigorous exercise, the body loses water and essential electrolytes, such as sodium, potassium, magnesium, and calcium, through sweat. This loss can disrupt the electrical signals that control muscle function, leading to involuntary contractions or cramps.
- Dehydration reduces blood volume and impairs muscle function, increasing the risk of cramps.
- Electrolyte imbalances, particularly low levels of sodium, potassium, magnesium, and calcium, can disrupt muscle contraction and relaxation.
- Heat-induced symptoms, such as heat cramps, heat exhaustion, and heat stroke, can also contribute to the development of EAMC. To prevent EAMC, it is essential to:
- Stay well-hydrated before, during, and after exercise by drinking water regularly 1.
- Consume electrolyte-containing sports drinks or foods, especially for exercises lasting longer than an hour.
- Gradually increase exercise intensity and duration to build muscle endurance.
- Incorporate strength training to improve overall muscle function and resilience.
- Be aware of the signs and symptoms of heat illness, such as headache, dizziness, faintness, nausea, coolness, cramps, and palpitations, and stop exercising immediately if any of these symptoms occur 1.
From the Research
Causes of Exercise-Associated Muscle Cramps (EAMC)
- EAMC are believed to be multifactorial in nature, stemming from an imbalance between excitatory drive from muscle spindles and inhibitory drive from Golgi tendon organs to the alpha motor neurons 2
- This imbalance is thought to result from neuromuscular overload and fatigue, rather than dehydration or electrolyte deficits 2, 3
- Disturbances at various levels of the central and peripheral nervous system and skeletal muscle are likely to be involved in the mechanism of cramp 4
- Exercise-induced muscle cramp may not be associated with gross disturbances of fluid and electrolyte balance 3
- Some cases of EAMC may be associated with disturbances of water and salt balance, while others appear to involve sustained abnormal spinal reflex activity secondary to fatigue of the affected muscles 5
Risk Factors for EAMC
- Neuromuscular fatigue and overload 2
- Intense exercise and exercise to fatigue 4
- Faulty posture and shortened muscle length 4
- Dehydration and electrolyte imbalances may contribute to EAMC in some cases, but the evidence is not conclusive 6, 3, 5