Young Ju, Ph.D.

Athletes in almost every type of sports, including and especially tennis, experience muscle cramps (aka exercise-associated muscle cramps or EAMCs) during or shortly after exercise. Despite the high prevalence of EAMCs, their causes, risk factors, and underlying mechanisms are not well understood. There are many home remedies for treatment or prevention of cramps. Some may reduce cramping; some may not. The purpose of this article is to address why we have EAMCs and what we can do to relieve them.

EAMC (1)

Muscle cramping is characterized as a temporary, painful, and involuntary contraction of a muscle or a muscle group. EAMCs are the most common muscle cramps caused by long and excessive exercise with the highest reported prevalence in a study on triathlons (2). There are also other types of muscle cramps which are associated with many factors, such as liver disease, hypothyroidism, stroke, malnutrition, certain medications (e.g., blood pressure medications), neuromuscular disorders, neurodegenerative disease (e.g., Parkinson’s disease), and nocturnal leg cramps of the elderly, etc. This article is focusing on EAMC.

Although there is no clear understanding of the EAMC mechanism, two main categories of theories have been put forward.

Dehydration, Electrolyte Imbalance, and Environmental Theories (3, 4)  During prolonged exercise, sweating and inadequate hydration may lead to fluid imbalance. These alterations can affect certain nerve pathways, alter excitability (neuronal firing), and cause electrolyte deficits–leading to a muscle cramp. However, the limited research measuring blood volume and electrolyte concentrations does not always support this hypothesis. Also, there is no study that actually measures hydration status. It appears, EAMCs are most frequent during hot and humid conditions (This type of cramping in environmental theory may also be referred to as heat cramps.). In particular, tennis players are at risk in competition with environmental factors, lengthy matches, and repeated bouts of competition. However, there is no clear association between body temperature and EAMC (5). 

Altered Neuromuscular Control Theory (6): Muscle fatigue could lead to overexcitation of the motor nerves. This newer theory suggests that the involuntary contraction of a muscle cramp occurs when nerve messages to the spinal column are altered, maybe due to muscle fatigue, resulting in an imbalance between muscle spindles and golgi tendon organs (Figure 1). Muscle spindles and golgi tendon organs work together reflexively to regulate muscle stiffness. Muscle spindles are sensory receptors that are located within skeletal muscles. Muscle spindles trigger a muscle action when the muscle spindle is stretched. Golgi tendon organs are sensory receptors that are located at the muscle-tendon junction. Golgi tendon organs detect changes in muscle tension and force produced by muscle contractions. If there is too much muscle tension, the golgi tendon organ will inhibit the muscle from creating any force, thus protecting from muscle injury. It appears that muscle fatigue increases muscle spindle excitation and decreases golgi tendon organ activity–leading to muscle cramps. The scientific evidence of this neuromuscular theory has been accumulating. These research findings are tending to prove that a fatigued muscle is unable to fully relax leading to the imbalance between excitatory signals to muscle spindles and inhibitory signals to the golgi tendon organs.

Signs and Symptoms (1, 8)

EAMCs usually occur acutely during or after exercise. People often report subtle muscle twitching before the EAMCs began (called cramping-prone state). Symptoms include sudden muscle pain, stiff muscles with the joint locked in its range of motion, and visible and palpable knotting. Athletes with more serious EAMCs may also have other serious medical conditions, e.g., low sodium. There is no validated and comprehensive cramp scale.

Contributing Factors (1, 9, 10, 11, 12)

There is a clear association between intense, extremely long-duration, high-intensity exercise and more skeletal muscle cramps. Also, there is a possible association between lack of training and/or training in a hot, humid environment and muscle fatigue and muscle cramping. Research also shows other potential factors including older age, a longer history of running, higher body mass index, shorter daily stretching time, irregular stretching habits, and a family history of cramping in the elderly. These factors need more research, but athletes and trainers need to be aware of them. Although the research shows that poor or inadequate stretching may predispose a person to muscle cramps, there is no evidence-based recommendation for what type of stretches and how much stretching should be done to reduce cramps.

Possible Prevention and Treatments (1, 8, 12)

While there is no standard treatment nor one single treatment that is proven, both nonpharmacological and pharmacologic options may be effective for you. These include stretching, rest, rapid-relief agents, pain-relief treatments, and rehydration.  

• Stretching: The fastest, safest, and most effective treatment is self-administered or clinician-administered gentle stretching. Generally, stretching may relieve muscle cramping which is often self-limiting. Regular stretching with proper body alignment after a training or exercise session is recommended.

• Rest: Lowering the intensity of or stopping exercise helps to normalize neuromuscular activity. If you are in the middle of a tennis match, currently, the United States Tennis Association (USTA) allows “one 3-minute medical timeout as needed”.

• Rapid-relief agents: If tolerable, substances can be considered for rapid relief such as pickle juice, mustard, and acetic acid. However, reported outcomes are mixed. 

• Pain-relief treatments: For severe cases, treatments like ice and heat, cryotherapy, massage, and electrical stimulation can be used to interrupt the pain-spasm cycle. Prescription medications for treatment of muscle cramps with known causes are also available; however, many of these agents show severe side effects.

• Rehydration: Rehydrating with water or carbohydrate-electrolyte beverages or intravenous fluids injection (among professional athletes) by a trained person may reduce duration/incidence.

Conclusions

Current research findings suggest that alteration in neuromuscular excitability is the predominant factor in muscle cramping; there is weak evidence for dehydration, electrolyte loss, and environmental factors in EAMC. Research evidence also supports that rest and gentle stretching are effective to relieve EAMC symptoms. However, there are limited studies regarding the best methods for EAMC prevention and treatment. It is also important to determine if muscle cramping is associated with exercise or with other health conditions. Therefore, rather than providing generalized advice, a multifaceted and targeted approach to an individual would be recommended. Talk to your health care providers who can help you and also refer you to other experts for related health problems.

Have you had successful results with improving your muscle cramping in tennis? Share your experiences (including when EAMC occurred, environmental conditions, methods and/or agents used etc) by emailing to my attention at info@nwto.us by Feb. 15.

People with any health problems should talk to their healthcare providers. This information is provided for your reference and you use at your own risk; you should rely on your medical professional for medical advice.

References

1. Dijkstra et al. Muscle cramps and contractures: causes and treatment. Prac Neurol 2023, 23:23.

2. Kantarowski et al. 620 Cramping studies in 2600 endurance athletes. Medicine & Sci in Sports & Exercise 1990, 22:S104.

3. Schwellnus et al. Aetology of skeletal muscle 'cramps' during exercise: A novel hypothesis. Journal of Sports Science, 1997, 15(3): 277.

4. Armstrong & Maresh. The exertional heat illness: a risk of athletic participation. Med Exerc Nutr Health 1993, 2:125.

5. Cooper et al. Exertional heat illness and environmental conditions during a single football season in the Southeast. J Athl Train. 2006, 41(3):332.

6. Giuriato et al. Muscle cramps: a comparison of the two-leading hypothesis. Journal of Electromyography and Kinesiology. 2018, 41:89.

7. Realzola & Kravitz. Ouch! What causes muscles to cramp. https://www.unm.edu/~lkravitz/Article%20folder/musclecramps.htmll

8. Miller et al. An evidence-based review of the pathophysiology, treatment, and prevention of exercise-associated muscle cramps. J Athletic Training 2022, 57(1):5.

9. Manjra et al. Risk factors for exercise associated muscle cramping (EAMC) in marathon 

10. Schwellnus et al. Increased running speed and previous cramps rather than dehydration or serum sodium changes predict exercise-associated muscle cramping: a prospective cohort study in 210 Ironman triathletes. Br J Sports Med 2010, 45:650.

11. Schwellnus. Muscle cramping in the marathon: aetiology and risk factors. Sports Med 2007, 37:364.

12. Troyer et al. Exercise-Associated Muscle Cramps in the Tennis Player. Current Reviews in Musculoskeletal Medicine 2020, 13:612.

This information is provided for your reference and you use at your own risk; you should rely on your medical professional for medical advice.