Muscle Cramping - Is Neuromuscular Control or Hydration Status to Blame?
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June 16, 2017
By Kristen Andrews, MS, RDN, CSCS
We all know the drill. Your athletes have been playing hard: sprinting to capture stray balls, out hustling the other team and staying focused as the game nears the final minutes. Then it happens. One of your players goes down and doesn’t get back up. You quickly stand to see what’s wrong. They’re grabbing their calf in pain; you have an immediate suspicion. They’re cramping.
What is the most effective way to treat your athlete? And furthermore, how do you decrease the likelihood of it happening again?
Muscle cramping, referred to as exercise associated muscle cramping (EAMC), is one of the most common medical conditions experienced by athletes during competition (Schwellnus et al., 2008).EAMC is a syndrome of “involuntary painful skeletal muscle spasms that occur during or immediately after physical exercise,” and most often affects the quadriceps, hamstrings and calves (Schwellnus et al., 2010). The prevalence of EAMC has been reported at 52% for rugby players, 60% for cyclist, and 67-68% for triathletes (Schwellnus et al., 2008).
While the experience of muscle cramping in sports is nearly universal, a clear understanding of the etiology is surprisingly lacking. There are many hypotheses, the most well-known of which-namely that dehydration and electrolyte depletion are to blame, is not well supported by research (Schwellnus et al., 2010). In fact, Schwellnus, Nicol, Laubscher, and Noakes (2004) found no relationship between serum electrolyte concentrations and hydration status and the occurrence of EAMC in long distance runners participating in a 56-kilometer race. Furthermore, researchers have documented EAMC occurring in athletes with serum sodium and potassium levels well within the normal rage (Murray et al., 2016).
If dehydration and electrolyte imbalances are not the cause of muscle cramping, what is? Muscle fatigue, leading to neuromuscular fatigue, and eventual loss of neuromuscular control has been investigated by researchers as a cause of EAMC since the late 1990’s (Schwellnus et al., 2010). According to the muscle fatigue hypothesis, “fatigue increases the muscle spindle afferent activity and decreases the Golgi tendon organ afferent activity, which may result in increased alpha motor neuron activity” (Schwellnus et al., 2010). In other words, the balance between the excitatory effects of muscle spindles and the inhibitory effects of Golgi tendon organs is lost, leading to uncontrolled contraction of the muscle fibers.
Two specific risk factors have been identified for the development of EAMC: a previous history of EAMC, and prolonged exercise at a greater relative intensity than normal training (Schwellnus et al., 2010). In addition, exercising in hot and humid environmental conditions has been linked to an increased risk for cramping (Schwellnus et al., 2008). Muscle cramping occurs incrementally. Skeletal muscle fatigue often experienced due to a lack of fitness acts as the first step in the chain reaction, followed by muscle twitching, spasmodic spontaneous contractions and complete muscle cramps if the exercise is not discontinued (Schwellnus et al., 2008).
Your best bet to decrease the occurrence of cramping is to adopt strategies which delay exercise-induced muscle fatigue, such as utilizing appropriate training and nutrition regimens (Nelson et al., 2016).
Preventing Muscle Cramps4
Follow these 5 recommendations to prevent the occurrence of EAMC
- Carefully track athletes’ training loads to ensure fitness levels are adequate to complete training and competitions.
- Guide EAMC prone athletes to complete exercise at lower intensities and for shorter durations than non-EAMC prone athletes.
- Encourage athletes to regularly stretch cramp-prone muscle groups.
- Ensure nutritional intake (consumption of carbohydrate specifically) during the period around exercise is adequate. Consult with a Registered Dietitian Nutritionist if necessary.
- Be aware that the occurrence of EAMC increases in hot and humid conditions; Be prepared to help athletes follow recommendations 1-4.
Managing Muscle Cramps4
Follow these 5 steps to manage an athlete experiencing EAMC:
- Immediately stop exercise and pull athlete aside for full assessment and diagnosis.
- Once EAMC is confirmed, begin passive stretching of the affected muscle groups (passive stretching increases muscle tension, effectively increasing the Golgi tendon organ’s inhibitory activity). Stretching should occur for 20-30 minutes or until cramping ceases.
- Encourage the consumption of carbohydrate containing fluids.
- Help the athlete return to a comfortable body temperature.
- If the athlete has recurrent EAMC, further assessment is indicated to exclude the possibility of an underlying medical condition.
- Murray, D., Miller, K. C., & Edwards, J. E. (2016).Does a Reduction in Serum Sodium Concentration or Serum Potassium Concentration Increase the Prevalence of Exercise-Associated Muscle Cramps? Journal of Sports Rehabilitation, 25, 301-304.
- Nelson, N. L., & Churilla, J. R. (2016). A narrative review of exercise-associated muscle cramps: Factors that contribute to neuromuscular fatigue and management implications. Muscle Nerve, 52(2), 177-185.
- Schwellnus, M. P., Nicol, J., Laubscher, R., Noakes, T. D. (2004). Serum electrolyte concentrations and hydration status are not associated with exercise associated muscle cramping (EAMC) in distance runners. British Journal of Sports Medicine, 38, 488-492.
- Schwellnus, M. P., Drew, N., & Collins, M. (2008). Muscle Cramping in Athletes- Risk Factors, Clinical Assessment, and Management. Clinical Sports Management, 27, 183-194.
- Schwellnus, M. P., Drew, N., & Collins, M. (2010). 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. British Journal of Sports Medicine. Doi: 10.1136/bjsm.2010.078535.
About the Author
Kristen Andrews is the Sports Dietitian for the US Men’s National team and the Los Angeles Galaxy, where she works with top national and international professional soccer players, as well as up-an-coming young stars, helping them to maximize their performance by being well-rounded, purposeful eaters. She is a Registered Dietitian Nutritionist, has a bachelor’s degree in dietetics from the University of Arkansas, a master’s degree in nutritional science from California State University Long Beach and is a Certified Strength and Conditioning Specialist.