The Complexity of Exercise-Associated Muscle Cramps: Evidence-Based Insights and Recommendations

Exercise-associated muscle cramps (EAMCs) are painful, involuntary muscle contractions that occur during or after exercise, primarily affecting muscles spanning multiple joints that are frequently used during physical activity. The severity of EAMCs can range from a “cramp-prone state” to mild (usually self-treatable and not limiting exercise performance) to serious (requiring medical intervention and exercise cessation). Factors such as neuromuscular excitability and the presence of systemic symptoms determine the clinical severity of EAMCs.

EAMCs are not related to body temperature and can occur in various ambient conditions. Terms like “heat cramps,” “spasms,” “contractures,” “tics,” “fasciculations,” and “tremors” are inaccurate descriptors for EAMCs, as they either lack pain or involve neuromuscular abnormalities.

EAMCs are a common condition among athletes, with the incidence varying based on factors such as sport, age, and sex. They are more frequent during hot months and can occur at rates ranging from 1.01 to 3.07 per 1000 athlete-exposures, depending on the sport and circumstances. Less experienced, older, and faster-paced athletes are at a higher risk of experiencing EAMCs.

A review of the EAMC literature published in Journal of Athletic Training examined the evidence to offer recommendations for evidence-based treatment and prevention strategies. While the exact underlying mechanisms of EAMCs may be subject to debate, recent research indicates that these cramps likely result from a combination of various intrinsic and extrinsic factors, rather than being attributed to a single cause.

Pathophysiology of exercise-associated muscle cramps

The pathophysiology of exercise-associated muscle cramps (EAMCs) has been explored through various theories:

1. Dehydration and Electrolyte Imbalance Theory: This theory suggests that EAMCs result from sweating, leading to a contracture of the interstitial fluid space, increased excitatory neurochemicals, and mechanical pressure on motor-nerve terminals. However, several studies and observations have challenged this theory, questioning the role of dehydration and electrolyte imbalances as the primary cause of EAMCs.
2. Altered Neuromuscular Control Theory: This theory proposes that EAMCs occur due to fatigue and other factors that disrupt the balance between excitatory and inhibitory stimuli at the α motor nerve. It suggests that alterations in neuromuscular control play a significant role in EAMC development, especially in muscles that cross multiple joints and contract in shortened positions.
3. Multifactorial Theory of EAMCs: This theory suggests that multiple intrinsic and extrinsic risk factors interact to elicit EAMCs. These factors coalesce through different pathways, leading to an imbalance in neuromuscular control and the induction of EAMCs. Factors such as muscle injury, deconditioning, pain, exercise intensity, and more may contribute to EAMC development.

In terms of diagnosis and treatment of acute EAMCs, diagnosis is typically based on clinical examination and history. Patients may experience muscle twitching before the onset of EAMCs, and cramping muscles become rigid. Stretching is often the first-line treatment, followed by rehydration with oral fluids (water or carbohydrate-electrolyte beverages), rest, and pain-relieving agents. Some individuals also use transient receptor potential receptor agonists (e.g., pickle juice) to relieve EAMCs, although the evidence is limited. Other remedies like bananas and quinine have been explored but are not strongly recommended for EAMC treatment.

The diagnosis and treatment of chronic or recurrent exercise-associated muscle cramps

The diagnosis and treatment of chronic or recurrent exercise-associated muscle cramps (EAMCs) involve several key steps. First, a comprehensive medical evaluation should be conducted to identify any intrinsic risk factors such as a history of injury, chronic medical conditions, medications, or allergies. If an underlying condition is found, it should be treated before addressing EAMC prevention.

Once intrinsic factors are ruled out, clinicians should assess for extrinsic or intrinsic risk factors such as pain, previous EAMCs, muscle damage or injury, prolonged exercise durations, and faster finishing times than expected. Realistic goal-setting, adequate sleep, incorporating rest and recovery, and training conditions similar to competition can help mitigate these risk factors.

EAMCs are believed to be related to changes in the neuromuscular system, and questions about factors affecting nervous system excitability should be asked before and after each EAMC to identify consistent risk factors. Targeted prevention strategies can then be developed.

Preventing EAMCs involves various recommendations, but many lack strong scientific support. Hydration and electrolyte consumption alone should not be overemphasized, as excessive consumption can lead to problems like hyponatremia. A multifactorial approach to prevention is recommended, including education about EAMC causes and safe hydration practices, thorough medical examinations, and cautious implementation of prevention strategies.

Carbohydrate-electrolyte beverages and electrolyte supplements are commonly suggested but require further research to determine their effectiveness. Caffeine-containing sports drinks should be used with caution due to their potential to increase nervous system excitability.

Sodium supplementation has shown mixed results in studies, and more research is needed. Sweat testing can help assess hydration needs, but it requires specific equipment. Intravenous (IV) fluids are not recommended for prophylactic use, as oral rehydration is usually sufficient.

Prophylactic stretching is ineffective for preventing EAMCs. Neuromuscular retraining through exercise, focusing on muscle balance, strength, and endurance, may hold promise for prevention. Ensuring appropriate work-to-rest ratios during exercise is also important to prevent EAMCs, as fatigue is a contributing factor.

Summary

In the past century, our understanding of exercise-associated muscle cramp (EAMC) causes has evolved. Recent research suggests that alterations in neuromuscular excitability, and to a lesser extent, dehydration and electrolyte losses, play significant roles in their development. Strong evidence supports EAMC treatments involving rest and gentle stretching, followed by addressing the underlying factors.

However, there is limited patient-oriented evidence regarding EAMC prevention methods. Instead of offering general advice, it is recommended that clinicians adopt a multifaceted and personalized approach, considering an individual’s unique risk factors when attempting to prevent EAMCs.