What Is an Exercise-Associated Muscle Cramp (EAMC)?
EAMC’s can be defined as “painful, involuntary contractions of skeletal muscle that occur during or immediately after exercise and are common in endurance athletes.”1 Possible triggers for cramps include: history of cramping, salt loss, poor fitness, fatigue, muscle injury, intense exercise and dehydration.
Early research suggested that muscle cramps were caused by dehydration and/or electrolyte imbalances (especially sodium) often associated with high rates of sweating. But other research suggests otherwise. For example in a 2010 study of IRONMAN athletes by Schwellnus and associates, the researchers found that increased running speed and previous history of cramping rather than dehydration or changes in sodium predicted exercise-related muscle cramping.2 Another study by Braulick and colleagues in 2013 found that serious dehydration does not alter muscle cramp susceptibility when fatigue and intensity are controlled.3
More recent research suggests that cramping most likely results from hyperexcitability of motor neurons that result in a failure of neuromuscular control. A motor neuron is the nerve cell that connects the spine (nervous system) to the muscle. Muscle contraction is controlled by electrical nerve impulses from nerves in the spinal cord to the motor neuron, which activates the muscle. If the motor neuron becomes hyperexcited, it essentially keeps telling the muscle to contract again and again and again (i.e. cramping)
Stopping Cramping by Disrupting the Hyperexcited Motor Neurons
Transient receptor potential channels (TRP channels) are a group of ion channels located in the mouth, esophagus and stomach that regulate the flow of ions – charged particles like sodium [Na+] and potassium [K+] – across cell membranes. TRP channels mediate sensations like pain, warmth or coldness, hotness, different kinds of tastes, vision and pressure. TRP channels can be activated by ingesting naturally occurring food extracts like peppers, ginger and cinnamon.
Recent research suggests that ingesting naturally occurring TRPA1 and TRPV2 channel stimulators like cinnamon, chili peppers or mustard may reduce the intensity and/or duration of muscle cramps by interrupting the persistent firing of motor neurons through chemical neurostimulation.4,5
Common herbal compounds that stimulate TRPA1 and TRPV2 channels6 include:
- Capsicum (chili peppers) – TRPV1
- Ginger – TRPA1 and TRPV1
- Cinnamon – TRPA1
- Cloves – TRPA1
- Mustard – TRPA1
- Winter-green – TRPA1
So What Do the Experts Recommend?
The research is still relatively new so specific guidelines may not yet be available. However, in a presentation to IRONMAN University Coaches, researchers Murray, MacKinnon and Bean suggest the following for muscle cramp-prone athletes:7
- Follow established guidelines for hydration and nutrition.
- Pace yourself within limits.
- Experiment with spicy products consumed 15-30 minutes before exercise or at the first sign of a cramp.
Expect to see more nutritional supplement products on the market that contain spicy food extracts (like cinnamon, ginger, chili peppers and mustard).
David B. Glover, MSE, MS, CSCS
IRONMAN Certified Coach
Author of Full Time and Sub-Nine: Fitting Iron Distance Training into Everyday Life (eBook format)
- Schwellnus, Martin P. “Skeletal muscle cramps during exercise.” The physician and sportsmedicine 27.12 (1999): 109-115.
- Schwellnus, Martin P., Nichola Drew, and Malcolm Collins. “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 (2011): 650-656.
- Braulick, Kyle W., et al. “Significant and serious dehydration does not affect skeletal muscle cramp threshold frequency.” British journal of sports medicine 47.11 (2013): 710-714.
- Craighead, Daniel H., et al. “Orally Ingested Transient Receptor Potential (TRP) Channel Activators Attenuate the Intensity-Duration of Voluntarily Induced Muscle Cramps in Humans.” The FASEB Journal 30.1 Supplement (2016): lb706-lb706.
- Short, Glenn, et al. “Orally-administered TRPV1 and TRPA1 activators inhibit electrically-induced muscle cramps in normal healthy volunteers (S17. 003).”Neurology 84.14 Supplement (2015): S17-003.
- Vriens, Joris, Bernd Nilius, and Rudi Vennekens. “Herbal Compounds and Toxins Modulating TRP Channels.” Current Neuropharmacology 6.1 (2008): 79–96. PMC. Web. 27 June 2016.
- Murray, Bob, Rod MacKinnon and Bruce Bean. “Rethinking the Cause of Exercise Associated Muscle Cramping.” IRONMAN Coaches Association: Research to Practice Lecture Series (February 2016).