Exercise Associated Muscle Cramps: Beyond Hydration

Exercise Associated Muscle Cramps (EAMCs) are involuntary contractions of the skeletal muscles that occur during or immediately following exercise. These painful, often unpredictable, spasms can last a few seconds or up to a few hours. Muscle cramps have been documented in a variety of athletes including 67% of triathletes and 30%-53% of American football players10.

The cause has long been attributed to dehydration, leading many athletes to supplement their diets with large quantities of fluid and electrolytes. However, decades of research have revealed the true etiology to be more complex with more than one plausible explanation.

Dehydration And Electrolyte Imbalance Theory

Loading up on sodium and other electrolytes came from the more than 100-year-old dehydration and electrolyte imbalance theory of muscle cramps. Early evidence of this theory was developed from observations of industrial workers in hot, humid environments who were believed to have cramped due to large fluid and electrolyte losses through sweat, or overconsumption of water3.

Despite these original beliefs, evidence of this theory in athletes derives mainly from small-scale, anecdotal studies. While cramp-prone athletes can be salty or heavy sweaters, dehydration itself is more of a systemic issue whereas the EAMCs observed in athletes are often localized or unilateral. Newer studies have found no difference in the hydration status of endurance athletes who cramp versus those who do not16.

In addition, EAMCs are frequently observed in moderate temperatures and in the absence of an electrolyte imbalance. While dehydration is certainly a factor in the development of EAMCs, it can not explain the cause of all muscle cramps.

Altered Neuromuscular Control Theory

The newer altered neuromuscular control theory hypothesizes that EAMCs result from signaling disturbances between the muscle and brain secondary to muscular fatigue. It is now believed that, when contracted into a shortened position, a fatigued muscle can experience a combination of increased excitatory activity in the muscle spindles and decreased inhibitory activity in the golgi tendon organ (GTO). As a result of this signal imbalance, the muscle loses its ability to “turn off,” leading to a sustained involuntary contraction. This is exacerbated by muscle-overload and repetitive strenuous exercise10.

Treatment & Prevention Strategies

In addition to the theories mentioned above, other risk factors playing a role include previous injury, genetics, and cramping history17. Since general muscle fatigue can lead to altered neuromuscular control, anything creating excess fatigue can increase risk too. This could include repetitive movement, attempting unaccustomed exercise or being under trained, low energy availability, and inadequate sleep. EAMCs are multifactorial, so we must consider the multiple mechanisms in action when assessing potential causes and searching for effective interventions.

From a nutrition standpoint, stimulating transient receptor potential (TRP) channels in the mouth and esophagus may be one solution. These receptors help send sensory information from the mouth → brain → muscles to decrease that neurological hyperexcitability, consequently alleviating the cramp2. Two major compounds that have been found to stimulate these receptors and help athletes manage EAMCs are acetic acid and capsaicin.

Acetic Acid

Pickle juice and mustard are common sources of acetic acid used to relieve muscle cramps in athletics11. Consuming 1 ml/kg body weight of pickle juice has been shown to decrease the duration of a cramp by 45%12. While this effect has long been attributed to electrolyte replacement, there are likely alternate explanations. First, the electrolyte content in the usual 1-3 fl oz. dose of pickle juice may be too low to make a substantial difference in serum electrolyte concentrations. In addition, pickle juice theoretically slows down digestion which would not allow enough time for the electrolytes to get absorbed and circulated to the cramping muscle. Instead, it is speculated that the acetic acid triggers TRP receptors to decrease the excitatory response in cramping muscles. In fact, ingesting a capful of vinegar alone alleviated a muscle cramp within 35 seconds19.

Capsaicin

Capsaicin, the active component in hot peppers, is another compound used to attenuate muscle cramps. The heat and spice trigger TRP receptors in the mouth to counteract neuromuscular fatigue1. The theoretical mechanism behind this is an increase in calcium reuptake in the working muscle, thereby contributing to muscular relaxation5. The specific dose of capsaicin to elicit these effects is still in question, however it is generally recommended to start small as gastrointestinal distress can occur from overconsumption. Access to products containing capsaicin may be a barrier compared to the use of pickle juice or mustard.

While both acetic acid and capsaicin can trigger inhibitory supraspinal reflexes, the research is still in its infancy and so far inconclusive. Both are generally well-tolerated assuming the athlete does not have a related allergy. However, these compounds may only help alleviate an active muscle cramp rather than prevent a future one. With that, what can be done to help our athletes combat EAMCs? Refer to the checklist below.

  1. Prioritize fueling. Inadequate carbohydrate intake and glycogen depletion can induce early muscle fatigue and cause cramping. Excessive caffeine and other stimulants may also increase EAMC susceptibility and should be limited14.
  2. Acclimatize to the training conditions. Heavy exercise in hot environments or high altitudes can increase risk of EAMCs. Gradual acclimatization over 1-2 weeks is typically recommended6.
  3. Passively stretch. As mentioned, fatigued muscles contracting in a shortened position are at a higher risk for motor neuron hyperexcitability. Passive stretching triggers the GTO to inhibit further muscle tension8.
  4. Hydrate. Muscles are 75% water. Even mild dehydration (<2% body water loss) can contribute to muscle fatigue and significantly impair both physical and cognitive performance. Simple ways to monitor hydration status include analyzing urine color and body weight.
  5. Add electrolytes. Sodium is the primary electrolyte lost in sweat. Encourage heavy sweaters to salt their food, choose salty snacks, and utilize carbohydrate-electrolyte beverages around exercise.
  6. Try TRP agonists. If an athlete is actively cramping, introduce products that can help reset excited motor neurons. In addition to acetic acid and capsaicin mentioned above, cinnamon and ginger can also be TRP receptor agonists13. When successful, these products will work within the first couple of minutes of ingestion.

Our current understanding is that EAMCs are not one-dimensional. There are many different causes, and sodium is not the only solution. With our new knowledge of neuromuscular excitability, the foundation of EAMC management should include proper nutrition and adequate training without excluding the possibility of dehydration and electrolyte imbalances. This could be supplemented with acetic acid, capsaicin, or other TRP agonists when an athlete is actively cramping. Since multiple mechanisms are involved, it is crucial to collaborate with other disciplines to help athletes reduce their risk of developing EAMCs altogether.

This article was written by Rachel Sachs, MS, RDN, a Collegiate and Professional Sports Dietitians Association Registered Dietitian (RD). To learn more about sports nutrition and CPSDA, go to www.sportsrd.org.

References

  1. Bevan, S., Quallo, T., Andersson, D.A. (2014). TRPV1. In: Nilius, B., Flockerzi, V. (eds) Mammalian Transient Receptor Potential (TRP) Cation Channels. Handbook of Experimental Pharmacology, vol 222. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-54215-2_
  2. Craighead, D.H., Shank, S.W., Alexander, L.M. and Kenney, W.L. (2016), Orally Ingested Transient Receptor Potential (TRP) Channel Activators Attenuate the Intensity-Duration of Voluntarily Induced Muscle Cramps in Humans. The FASEB Journal, 30: lb706-lb706. https://doi.org/10.1096/fasebj.30.1_supplement.lb706
  3. Dill, D.B., Bock, A.V., Edwards, H.T., Kennedy, P.H. (1936). Industrial Fatigue. Journal of Industrial Hygiene and Toxicology. Vol.18 pp.417-31 ref.35
  4. Georgieva, Julia, et al. Effectiveness of Mouth Rinsing versus Ingesting Pickle Juice for Alleviating Electrically Induced Cramp in Physically Active Adults. Applied Sciences, vol. 11, no. 24, 2021, p. 12096., https://doi.org/10.3390/app112412096.
  5. Giuriato, G., Venturelli, M., Matias, A., Soares, E., Gaetgens, J., Frederick, K. A., & Ives, S. J. (2022). Capsaicin and Its Effect on Exercise Performance, Fatigue and Inflammation after Exercise. Nutrients, 14(2), 232. https://doi.org/10.3390/nu14020232
  6. Heat stress: Acclimatization – centers for disease control and prevention. (n.d.). Retrieved November 1, 2022, from https://www.cdc.gov/niosh/mining/UserFiles/works/pdfs/2017-124.pdf
  7. Jahic, D., & Begic, E. (2018). Exercise-Associated Muscle Cramp-Doubts About the Cause. Materia socio-medica, 30(1), 67–69. https://doi.org/10.5455/msm.2018.30.67-69
  8. Malcolm, Corrine. (2019). Muscle Cramps: Causes and Remedies Based on Latest Science. CTS. https://trainright.com/muscle-cramp-cause-remedy.
  9. Maquirriain, J., & Merello, M. (2007). The athlete with muscular cramps: clinical approach. The Journal of the American Academy of Orthopaedic Surgeons, 15(7), 425–431. https://doi.org/10.5435/00124635-200707000-00007
  10. Maughan, R. J., & Shirreffs, S. M. (2019). Muscle Cramping During Exercise: Causes, Solutions, and Questions Remaining. Sports medicine (Auckland, N.Z.), 49(Suppl 2), 115–124. https://doi.org/10.1007/s40279-019-01162-1
  11. Miller, K. C., Electrolyte and Plasma Responses After Pickle Juice, Mustard, and Deionized Water Ingestion in Dehydrated Humans. J Athl Train 1 June 2014; 49 (3): 360–367. doi: https://doi.org/10.4085/1062-6050-49.2.23
  12. Miller, K. C., Mack, G. W., Knight, K. L., Hopkins, J. T., Draper, D. O., Fields, P. J., & Hunter, I. (2010). Reflex inhibition of electrically induced muscle cramps in hypohydrated humans. Medicine and science in sports and exercise, 42(5), 953–961. https://doi.org/10.1249/MSS.0b013e3181c0647e
  13. Miller, K.C, McDermott, B. P, Yeargin, S. W., Fiol, A., Schwellnus, M. P. (2022). An Evidence-Based Review of the Pathophysiology, Treatment, and Prevention of Exercise-Associated Muscle Cramps. J Athl Train 1 January 2022; 57 (1): 5–15. doi: https://doi.org/10.4085/1062-6050-0696.20
  14. Molema, M. M., Dekker, M. C., Voermans, N. C., van Engelen, B. G., & Aarnoutse, R. E. (2007). Caffeine and muscle cramps: A stimulating connection. The American Journal of Medicine, 120(8). https://doi.org/10.1016/j.amjmed.2006.07.035
  15. O’Neill, J., Brock, C., Olesen, A. E., Andresen, T., Nilsson, M., & Dickenson, A. H. (2012). Unraveling the mystery of capsaicin: a tool to understand and treat pain. Pharmacological reviews, 64(4), 939–971. https://doi.org/10.1124/pr.112.006163
  16. Schwellnus, M. P., Drew, N., & Collins, M. (2011). 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, 45(8), 650–656. https://doi.org/10.1136/bjsm.2010.078535
  17. Troyer, W., Render, A., & Jayanthi, N. (2020). Exercise-Associated Muscle Cramps in the Tennis Player. Current reviews in musculoskeletal medicine, 13(5), 612–621. https://doi.org/10.1007/s12178-020-09662-8
  18. Williams RB, Conway DP. (2000). Treatment of Acute Muscle Cramps with Pickle Juice: A Case Report. J Athl Train. 2000;35(suppl2):S24
  19. Williams R, Conway D. Treatment of acute muscle cramps with vinegar: a case report. J Athl Train. 2001;36:S106.

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