What Causes Exercise Associated Muscle Cramps?

What Causes Exercise Associated Muscle Cramps?

No matter if you’re an elite or a newbie, just about every athlete has experienced a muscle cramp at some point. Exercise associate muscle cramps are a struggle for many athletes. There’s plenty of advice on the internet and products on the market that claim they can prevent or cure muscle cramps with hydration and electrolytes. However, physiology experts agree that exercise-associated muscle cramping is multi-factorial.

What Is A Muscle Cramp?

A muscle cramp is a sudden and involuntary contraction of one or more muscles with delayed relaxation. Contraction = shortening of the muscle. It’s actually not entirely well understood. It’s also a common misconception that exercise associated muscle cramping is a single condition or one cause. A cramp could range in severity by affecting single muscle group or multiple muscle groups. 

Old School Of Thought

Dehydration and Electrolyte Imbalances

Cramping during exercise was previously thought to be a dehydration and/or electrolyte balance issue. An argument against electrolyte imbalances as a cause for most cramps is, if that were the primary culprit, then we would likely see systemic cramping, rather than cramping in isolated muscles. That’s not suggesting that hydration isn’t important- appropriate hydration can delay fatigue, which may play a role in muscle cramp prevention. Hyponatremia (low sodium, overhydration) can also cause systemic (whole body) cramping. Additionally, current literature doesn’t support this theory.

A study in 2011 looking into the causes of muscle cramps followed 210 ironman triathletes during an ironman. Blood samples were taken prior to the race on all athletes to determine electrolyte imbalances prior to racing. Of the 210 athletes, 43 experienced cramps during the race. Blood samples were collected post-race and no difference in occurrence of dehydration and electrolyte imbalances was found in the cramping group versus the non-cramping group. In fact, history of cramping and running speed was a much larger association with cramps during the race!


New School Of Thought // Latest Theory

Altered Neuromuscular Control Theory:

ANCT is the latest theory to explain exercise-induced muscle cramps. When a muscle is fatigued, it becomes more likely to misfire. This refers to the spindle activity that regulates the knee-jerk reaction (think about when a doctor uses the little rubber mallet on your knee). Fatigued muscle is actually more prone to contracting than it is relaxing. So, during muscle fatigue, the muscle becomes more excitable and less able to relax. 

Fatigue is the more likely culprit for muscle cramping! Cramping tends to also happen more at the start of the race season, when one is likely not in peak shape. Additionally, most cramps happen toward the end of race or after the race. Interestingly, studies also show athletes with faster race times tend to cramp more than the slower athletes. 


Some People Are More Prone To Cramping:

However, it does appear that certain athletes are more prone to cramping. Males tend to cramp more than females. Older men are more prone than younger men. Some lab models with induced cramps noted that cramping thresholds differ between individuals- participants with a lower threshold to cramping (via electrical stimulation) reported cramping more in races!  A couple studies on ironman triathletes showed an association among athletes who cramp and also have a family history of exercise-associated muscle cramping and associations with cramping and history of tendon/ligament injuries. 

Other Factors in Exercise-Associated Muscle Cramping:

  • You could be glycogen depleted
  • Hyponatremia (low sodium and also known as overhydration) can cause whole body cramps
  • Your medication could play a role. Cramping is a common side effect of statin drugs.


  • Eat Spicy Foods – You may have heard of some spicy tasting products (like Hotshot) to treat exercise muscle cramps. While the science is sound, these may be treating the symptom and not the underlying cause of the cramp. However, they seem to work!
  • Stretch – Gently stretching the muscle can help the muscle to relax.
  • Massage – Pushing on the muscle can help it relax.
  • Hyperventilate – I have personally found this helpful for side-stitches. And it’s as weird as it sounds! Rapid breathing where you are exhaling more than inhaling. 


  • Train harder! Make sure you are building duration and intensity. Make sure you include race-effort based workouts.
  • Have a fueling/hydration plan and practice it. You actually need to train your gut to tolerate fluid and calories which will set you up for peak performance.
  • Appropriately taper so you are super fresh on race day.
  • Runners should have their running form evaluated to prevent over-using certain muscle groups.
  • Cyclists should be appropriately fitted for their bike.
  • Rock climbers aiming for multipitch climbs with long and/or steep approaches should train for the approach and the climbing.
  • Although current literature suggests fatigue as the likely culprit, researchers emphasize that exercise associated cramping is complicated and more research is needed to hone in on better prevention methods, especially for those more prone to cramping.


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. Br J Sports Med, 45(8), 650-656. doi: 10.1136/bjsm.2010.078535

Miller, K. C., Mack, G. W., Knight, K. L., Hopkins, J. T., Draper, D. O., Fields, P. J., et al. (2010). Three percent hypohydration does not affect threshold frequency of electrically induced cramps. Med Sci Sports Exerc, 42(11), 2056-2063. doi: 10.1249/MSS.0b013e3181dd5e3a

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, 54(2), 177-185. doi: 10.1002/mus.25176

Schwellnus, M. P. (2009). Cause of exercise associated muscle cramps (EAMC)–altered neuromuscular control, dehydration or electrolyte depletion? Br J Sports Med, 43(6), 401-408. doi: 10.1136/bjsm.2008.050401

Schwellnus, M. P., Allie, S., Derman, W., & Collins, M. (2011). Increased running speed and pre-race muscle damage as risk factors for exercise-associated muscle cramps in a 56 km ultra-marathon: a prospective cohort study. Br J Sports Med, 45(14), 1132-1136. doi: 10.1136/bjsm.2010.082677

Schwellnus, M. P., Derman, E. W., & Noakes, T. D. (1997). Aetiology of skeletal muscle ‘cramps’ during exercise: a novel hypothesis. J Sports Sci, 15(3), 277-285. doi: 10.1080/026404197367281

Shang, G., Collins, M., & Schwellnus, M. P. (2011). Factors associated with a self-reported history of exercise-associated muscle cramps in Ironman triathletes: a case-control study. Clin J Sport Med, 21(3), 204-210. doi: 10.1097/JSM.0b013e31820bcbfd

Behringer Michael, Nowak Stephanie, et al. Effects of TRPV1 and TRPA1 activators on the cramp threshold frequency: a randomized, double-blind, placebo-controlled trail. European Journal of Applied Physiology, 117(8), 1641-1647. doi: 10.1007/s00421-017-3653-6.

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