Your Basic Trainer

Library / Conditions

Muscle cramps

Also called exercise-associated muscle cramps, exercise-associated muscle cramp, EAMC, muscle cramp, cramp, cramps

Painful, involuntary muscle contractions during or soon after exercise. How reviews define them, who reports them, the two competing explanations, and what small laboratory studies of drinks and stretching found.

Region
Across the body
Muscles
quadriceps, hamstrings, gastrocnemius
Updated
October 15, 2026
Reviewed
October 15, 2026 · how entries are checked

What it is

How reviews define a cramp

A 2022 evidence-based review describes exercise-associated muscle cramps as involuntary, painful tightening of a skeletal muscle while exercising or soon after1. A 2026 systematic review, a study that searches for all the research on a question in a set, checkable way, used a near-identical definition3. The 2022 review states that these cramps typically strike hard-working muscles that cross more than one joint, such as the quadriceps1. The same review calls “heat cramps” an inaccurate name, since the cramps are unrelated to body temperature1.

The 2022 review describes a scale of severity1. It runs from a cramp-prone state, through mild cramps that usually do not limit exercise, to serious cramps1. Serious cramps force a stop and come with other whole-body signs1.

Two explanations

A 2019 review describes two main proposed causes and states that the evidence for each side is weak2. It appeared in a journal supplement supported by the Gatorade Sports Science Institute, a division of PepsiCo2. One cause is a disturbance of water and salt balance; the other lies in the nervous system2.

  • Water and salt. The same review reports early industrial studies of steel mill workers2. Adding saline (sterile salt water) to the drinking water of 12,000 workers almost abolished cramps, against nearby mills on plain water2.
  • Nerve control. A 2022 review describes the altered neuromuscular control theory1. In it, fatigue and other factors upset the balance of “go” and “stop” signals at the motor neuron, the nerve cell that drives muscle fibres1,9.

Three reviews favour the nerve explanation, and one of them is by an author of the 2022 review1,10,11,12. A 2009 review by Martin Schwellnus alone states that data are building in support of it, though more evidence is needed1,10. A 2016 narrative review, a summary written without a set search method, points to an imbalance between two kinds of sensor11. These are muscle spindles (stretch sensors in the muscle) and Golgi tendon organs (tendon sensors)11. A 2018 review of 69 papers concludes the nerve explanation may prevail, with recent evidence pointing to the spinal cord12.

The 2022 review notes that well-trained athletes still cramp, so fatigue is not the sole cause1. The same review says recent evidence points to a mix of internal and external factors1. The 2019 review concludes there are likely different types of cramp with different triggers2.

Who it affects

How often it is reported

A 2019 review notes that its own figures by sport mix single-event and lifetime rates2.

Group studiedWhat was countedFigure
IRONMAN World Championship, 49,530 entrantsCramps seen in the medical tent57.8 per 1,000 entrants13
Two Oceans Marathon entrants, 21.1 and 56 kmEver had cramps while exercising12.8% overall; 20.0% at 56 km, 8.5% at 21.1 km14
Cycling race, 21,460 entrantsEver had cramps while exercising30.5%15
103 male rugby league players, one seasonAt least one calf cramp52 players, about half16
Triathletes; marathoners or endurance cyclists; American football players (2019 review)Cramps, single-event and lifetime rates mixed67%; 18 to 70%; 30 to 53%2
Endurance events (2026 systematic review)At least one crampAbout one quarter; up to 40% in ultramarathons, races longer than a marathon3

Where, when and how badly

Among Two Oceans entrants, cramps most often began in the last quarter of a race, and the calves were the muscles most often affected14. In that survey, 95% of cramps were mild to moderate14. Among the cyclists, cramps were mainly in the quadriceps and in the last quarter of a race15. The 2022 review states that most people can finish after mild cramps, though some athletes cannot complete their event1. In a 4-year study of 65,865 road race starters, serious cramping was among the most common specific medical problems17.

What goes with it

In the 2026 meta-analysis, a history of cramps was linked with about 4.4 times the odds of a further episode3. It found strong evidence of no link with age, body mass or height3. Most of its findings rested on limited evidence, and every included study controlled poorly for confounders, other factors that could explain a link3. Its studies were of triathletes, distance runners and rugby players, mostly men aged 18 to 453.

Single studies that followed athletes forward in time also point to past cramps, and two point to pace18,19:

  • In 210 Ironman triathletes, faster race time and a history of cramps were the only two independent risk factors18.
  • In 49 runners in a 56 km race, past cramps and a faster pace over the first 28 km were risk factors19.
  • In 103 rugby league players, past calf cramps, competition level and past low back pain that cost field time predicted calf cramps16.

What studies found

Water and salt in race studies

A 2009 review states that the support for fluid and salt loss as causes comes mainly from anecdote, case series and one small case-control study10. A case-control study compares people who have a condition with similar people who do not. The case series held 18 cases in all, and four prospective cohort studies, which follow people forward in time, do not support these causes10. Two race studies found no difference in body salts or fluid between those who cramped and those who did not18,21:

  • In 210 Ironman triathletes, the 43 who cramped did not differ in blood electrolyte (body salt) or body weight changes18.
  • In 88 marathon finishers, the 20 who cramped did not differ in fluid or blood salt measures21. They had higher creatine kinase and lactate dehydrogenase, markers of muscle damage21.

Across 30 years of IRONMAN World Championship records, athletes with cramps had lost more weight, and dehydration was linked with cramping13. Blood sodium and potassium did not differ, and the authors note the result goes against earlier findings13. The newer 2026 meta-analysis partly agrees with the 2009 review: it found no consistent link with body mass change or sodium3. It did find higher post-race potassium in people who cramped, on moderate evidence3. The 2019 review argues that blood tests may miss changes inside the muscle, and are usually taken after the cramp has passed2.

Drinks in the laboratory

Laboratory models bring on a cramp with hard contractions of small, shortened muscles, or with electrical stimulation2. That means small currents applied through the skin to make a muscle contract. The 2019 review states that such models show dehydration does not change the stimulation needed to start a cramp2. It adds that their relevance to cramps during exercise is questionable2.

  • Sports drink, 13 men. In 13 men prone to cramps exercising in heat, 9 cramped with a carbohydrate-electrolyte drink and 7 when underhydrated22. In the 7 who cramped both times, cramps came later with the drink: 36.8 against 14.6 minutes22.
  • Water or a rehydration drink, 10 men. Two crossover studies, in which each person tries every option in turn, ran 10 men downhill in heat5,23. Plain water lowered the stimulation needed to cause a calf cramp5,23. An oral rehydration solution raised it5,23.
  • Electrolyte drink, 9 people. A study of 9 cramp-prone people compared an electrolyte drink with a placebo (dummy) drink4. The drink slightly raised the stimulation needed to cause a cramp and lowered reported pain, but no participant was kept from cramping4.
  • Pickle juice, dehydrated men. In men who had lost about 3% of body weight, an electrically induced foot cramp lasted 49.1 seconds less after pickle juice than water24. Blood composition changed little24. The 2019 review states this was not a study of exercise cramps, so it cannot count as evidence for them2. That review adds that an effect of trial order was not ruled out2.

The authors of the 13-man study concluded that fluid and salt loss are not the sole causes22. The 2026 systematic review states that current evidence does not show a consistent benefit from electrolyte supplements, though its own analysis covered risk factors3. The 2022 review states that overemphasis on fluids and salts against cramps contributed to two high school athletes’ deaths in 20141. The cause was hyponatremia (low blood sodium)1.

Stretching

The 2022 review assessed stopping exercise and stretching gently until a cramp eases, and the review graded this evidence as strong1. The same review states that which kind of stretch works best on an active cramp has not been studied1.

Held stretches before testing did not change cramp measures, and stretching habits did not predict who cramped6,25,26. In a crossover study of 17 healthy college-aged people, a held stretch did not change the stimulation needed to cause a foot-muscle cramp6.

A crossover study of 15 people used 3 minutes of held or proprioceptive neuromuscular facilitation stretching, which mixes held stretches with contractions25. Big-toe range rose, but cramp threshold, a laboratory measure of cramp proneness, did not change25. Its Crossref record, filed by the publisher, names a Central Michigan University research office as the funder25. A 2024 short summary of the best few studies found stretching habits did not predict who cramped in competition26.

Kevin Miller, first author of the 2022 review, also led the 15-person stretching study and the pickle juice study1,24,25,26. The 2022 review’s references for those two studies are his own papers1. He is also the second of two authors of the 2024 summary1,24,25,26.

Other approaches

  • Spicy-ingredient drinks, 39 people. A double-blind crossover trial compared a drink of TRP-channel activators (spicy ingredients) with a flavoured control drink7. The active drink delayed a voluntarily induced calf cramp, 36.9 against 27.8 seconds, and lowered muscle activity, but left its length unchanged7. Flex Pharma funded it, and a placebo with the same spicy taste could not be made7. One author later joined the firm’s advisory board, with no conflicting tie during the experiments7.
  • TRP-activator mixture, 22 men. A double-blind, placebo-controlled trial randomly assigned 22 healthy men27. TRP-channel activators had a small, short-lived effect on the stimulation needed to cause a calf cramp, and none on cramp intensity or pain27. Flex Pharma gave the mixture free; the authors state it had no role in the study and that no grant funded it27.
  • The 2022 review on these drinks. It notes that in one such trial everyone still cramped, and that more work is needed1.
  • Dry needling. A single-blind trial, in which one party does not know who is in which group, studied 62 marathon and half-marathon runners28. One session of dry needling, fine needles put into a muscle, did not change post-race cramping against sham (dummy) needling28. Its authors report no conflicts of interest28.
  • Magnesium. A 2020 Cochrane review, a systematic review done to the Cochrane Collaboration’s standards, covered 11 trials and found no trial of magnesium for exercise cramps29.

A 2021 Cochrane review covered randomised trials of non-drug approaches for lower limb cramps, each tested over at least four weeks8. It found no study that tested such an approach during exercise8. The 2022 review states that most advice on preventing these cramps lacks strong support from studies in people, or rests on anecdote1.

Connections

The 2022 review links these cramps with muscles that cross more than one joint1. The rectus femoris is the only quadriceps muscle that crosses two joints, the hip and the knee30. Three of the hamstrings cross both the hip and the knee31. The muscle tissue page covers how motor neurons switch fibres on9.

One survey of race entrants linked a history of cramps with past muscle and tendon injury20. Those injuries have their own pages, muscle strain and tendinopathy20. A 2016 article names a tear of the medial (inner) gastrocnemius as the most common calf injury in runners32. That injury is covered on the calf strain page32.

Several of the counts above come from road race entrants, and running has its own page14,20. The calf stretch page covers a trial of night-time cramps in people aged 55 and over, not cramps in sport8.

Muscle cramps is an involuntary contraction of

Muscle cramps was most often reported in one cycling survey in

Muscle cramps was most often reported in one road race survey in the calf, which includes

Muscle cramps is described by one review as typical of muscles crossing more than one joint, which include

Muscle cramps was linked in one survey of race entrants with a history of muscle injury, the subject of

Muscle cramps was linked in one survey of race entrants with a history of tendon injury, the subject of

Muscle cramps has a Cochrane-reviewed trial, in people aged 55 and over with night-time cramps, of

Muscle cramps has been counted in road race studies of

Sources

  1. Miller KC, McDermott BP, Yeargin SW, Fiol A, Schwellnus MP (2022). An Evidence-Based Review of the Pathophysiology, Treatment, and Prevention of Exercise-Associated Muscle Cramps.. Journal of athletic training. doi:10.4085/1062-6050-0696.20 PMID 34185846
  2. Maughan RJ, Shirreffs SM (2019). Muscle Cramping During Exercise: Causes, Solutions, and Questions Remaining.. Sports medicine (Auckland, N.Z.). doi:10.1007/s40279-019-01162-1 PMID 31696455
  3. Costa LDS, Correa VAF, de Oliveira VF, Jahn AJS, Aliano GB, Nunes GS (2026). Risk Factors for Exercise-Associated Muscle Cramps: A Systematic Review With Meta-Analysis.. Muscle & nerve. doi:10.1002/mus.70389 PMID 42693659
  4. Earp JE, Stearns RL, Stranieri A, Agostinucci J, Lepley AS, Matson T, Ward-Ritacco CL (2019). Electrolyte beverage consumption alters electrically induced cramping threshold.. Muscle & nerve. doi:10.1002/mus.26650 PMID 31350753
  5. Lau WY, Kato H, Nosaka K (2019). Water intake after dehydration makes muscles more susceptible to cramp but electrolytes reverse that effect.. BMJ open sport & exercise medicine. doi:10.1136/bmjsem-2018-000478 PMID 30899546
  6. Panza G, Stadler J, Murray D, Lerma N, Barrett T, Pettit-Mee R, Edwards JE (2017). Acute Passive Static Stretching and Cramp Threshold Frequency.. Journal of athletic training. doi:10.4085/1062-6050-52.7.03 PMID 28796528
  7. Craighead DH, Shank SW, Gottschall JS, Passe DH, Murray B, Alexander LM, Kenney WL (2017). Ingestion of transient receptor potential channel agonists attenuates exercise-induced muscle cramps.. Muscle & nerve. doi:10.1002/mus.25611 PMID 28192854
  8. Hawke F, Sadler SG, Katzberg HD, Pourkazemi F, Chuter V, Burns J (2021). Non-drug therapies for the secondary prevention of lower limb muscle cramps.. The Cochrane database of systematic reviews. doi:10.1002/14651858.CD008496.pub3 PMID 33998664
  9. Betts JG, Young KA, Wise JA, Johnson E, Poe B, Kruse DH, Korol O, Johnson JE, Womble M, DeSaix P (2022). Anatomy and Physiology 2e. OpenStax. Link
  10. Schwellnus MP (2009). Cause of exercise associated muscle cramps (EAMC)--altered neuromuscular control, dehydration or electrolyte depletion?. British journal of sports medicine. doi:10.1136/bjsm.2008.050401 PMID 18981039
  11. Nelson NL, Churilla JR (2016). A narrative review of exercise-associated muscle cramps: Factors that contribute to neuromuscular fatigue and management implications.. Muscle & nerve. doi:10.1002/mus.25176 PMID 27159592
  12. Giuriato G, Pedrinolla A, Schena F, Venturelli M (2018). Muscle cramps: A comparison of the two-leading hypothesis.. Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology. doi:10.1016/j.jelekin.2018.05.006 PMID 29857264
  13. Nilssen PK, Johnson KB, Hiller WDB, Miller TK, Connolly CP (2024). Exercise-Associated Muscle Cramps in Ironman-Distance Triathletes Over 3 Decades.. Clinical journal of sport medicine : official journal of the Canadian Academy of Sport Medicine. doi:10.1097/JSM.0000000000001276 PMID 39405382
  14. de Jager I, Schwellnus M, Viljoen C, Korkie E, Sewry N, Swanevelder S, Jordaan E (2022). Prevalence, Clinical Characteristics, and Self-Reported Treatment of Exercise-Associated Muscle Cramping Differ Between 21.1- and 56-Km Running Race Entrants-SAFER XXII.. Clinical journal of sport medicine : official journal of the Canadian Academy of Sport Medicine. doi:10.1097/JSM.0000000000000992 PMID 34759185
  15. Pohl C, Schwellnus M, Sewry N, Boer P, Jordaan E, Viljoen C (2026). Independent risk factors associated with a history of exercise associated muscle cramps (EAMC) among 21460 cycling race entrants (SAFER XXXVI): a descriptive cross-sectional study.. Brazilian journal of physical therapy. doi:10.1016/j.bjpt.2025.101559 PMID 41418715
  16. Summers KM, Snodgrass SJ, Callister R (2014). Predictors of calf cramping in rugby league.. Journal of strength and conditioning research. doi:10.1519/JSC.0b013e31829f360c PMID 23774284
  17. Schwabe K, Schwellnus M, Derman W, Swanevelder S, Jordaan E (2014). Medical complications and deaths in 21 and 56 km road race runners: a 4-year prospective study in 65 865 runners--SAFER study I.. British journal of sports medicine. doi:10.1136/bjsports-2014-093470 PMID 24735839
  18. Schwellnus MP, 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. doi:10.1136/bjsm.2010.078535 PMID 21148567
  19. Schwellnus MP, 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.. British journal of sports medicine. doi:10.1136/bjsm.2010.082677 PMID 21402566
  20. Schwellnus MP, Swanevelder S, Jordaan E, Derman W, Van Rensburg DCJ (2018). Underlying Chronic Disease, Medication Use, History of Running Injuries and Being a More Experienced Runner Are Independent Factors Associated With Exercise-Associated Muscle Cramping: A Cross-Sectional Study in 15778 Distance Runners.. Clinical journal of sport medicine : official journal of the Canadian Academy of Sport Medicine. doi:10.1097/JSM.0000000000000456 PMID 28901963
  21. Martínez-Navarro I, Montoya-Vieco A, Collado E, Hernando B, Panizo N, Hernando C (2020). Muscle Cramping in the Marathon: Dehydration and Electrolyte Depletion vs. Muscle Damage.. Journal of strength and conditioning research. doi:10.1519/JSC.0000000000003713 PMID 32796418
  22. Jung AP, Bishop PA, Al-Nawwas A, Dale RB (2005). Influence of Hydration and Electrolyte Supplementation on Incidence and Time to Onset of Exercise-Associated Muscle Cramps.. Journal of athletic training. PMID 15970952
  23. Lau WY, Kato H, Nosaka K (2021). Effect of oral rehydration solution versus spring water intake during exercise in the heat on muscle cramp susceptibility of young men.. Journal of the International Society of Sports Nutrition. doi:10.1186/s12970-021-00414-8 PMID 33722257
  24. Miller KC, Mack GW, Knight KL, Hopkins JT, Draper DO, Fields PJ, Hunter I (2010). Reflex inhibition of electrically induced muscle cramps in hypohydrated humans.. Medicine and science in sports and exercise. doi:10.1249/MSS.0b013e3181c0647e PMID 19997012
  25. Miller KC, Harsen JD, Long BC (2018). Prophylactic stretching does not reduce cramp susceptibility.. Muscle & nerve. doi:10.1002/mus.25762 PMID 28796278
  26. Evers-Smith JW, Miller KC (2024). Does Prophylactic Stretching Reduce the Occurrence of Exercise-Associated Muscle Cramping? A Critically Appraised Topic.. Journal of sport rehabilitation. doi:10.1123/jsr.2022-0374 PMID 37758261
  27. Behringer M, Nowak S, Leyendecker J, Mester J (2017). Effects of TRPV1 and TRPA1 activators on the cramp threshold frequency: a randomized, double-blind placebo-controlled trial.. European journal of applied physiology. doi:10.1007/s00421-017-3653-6 PMID 28573374
  28. Cushman DM, Cummings K, Skinner L, Holman A, Haight P, Brobeck M, Teramoto M, Tang C (2021). Postrace Dry Needling Does Not Reduce Subsequent Soreness and Cramping-A Randomized Controlled Trial.. Clinical journal of sport medicine : official journal of the Canadian Academy of Sport Medicine. doi:10.1097/JSM.0000000000000794 PMID 32058451
  29. Garrison SR, Korownyk CS, Kolber MR, Allan GM, Musini VM, Sekhon RK, Dugré N (2020). Magnesium for skeletal muscle cramps.. The Cochrane database of systematic reviews. doi:10.1002/14651858.CD009402.pub3 PMID 32956536
  30. Begum FA, Kayani B, Chang JS, Tansey RJ, Haddad FS (2020). The management of proximal rectus femoris avulsion injuries.. EFORT Open Reviews. doi:10.1302/2058-5241.5.200055 PMID 33312709
  31. Koolmees DS, Klott JD, Poppe TR, Bernholt DL (2025). Distal Hamstring Injuries and Disorders.. Journal of the American Academy of Orthopaedic Surgeons: Global Research & Reviews. doi:10.5435/JAAOSGlobal-D-25-00248 PMID 40972536
  32. Fields KB, Rigby MD (2016). Muscular Calf Injuries in Runners.. Current sports medicine reports. doi:10.1249/JSR.0000000000000292 PMID 27618240

Every source the library cites

Changes

  • First published.