Almost every runner has experienced running cramps at one point or another.
Muscle cramps during a run can stop you dead in your tracks if they are severe enough; how many times have we seen sprinters bolting down the track only to stop abruptly, grabbing their hamstrings on one side, if not falling over in agony from an intense leg cramp?
Distance runners are also prone to muscle cramps during or after runs.
Dehydration and electrolyte imbalances may contribute to running cramps in some instances; however, the association between dehydration and muscle cramps has largely been debunked.
Instead, researchers theorize that the most common cause of exercise-induced muscle cramps is fatigue in the muscle fibers themselves and neuromuscular fatigue from running at a higher-than-normal intensity than your muscles are generally accustomed to.
This guide breaks down the most common causes of running cramps, the different types runners experience, and expert-backed strategies to prevent side stitches and muscle spasms during your runs.
Who Gets Running Cramps and Why? Patterns Among Different Runners
As a certified running and triathlon coach, I work with runners of all levels and distances, from beginners starting with walk/run intervals to competitive long-distance runners who are placing in their age group in large races, and even ultramarathon runners who are tackling 100-mile races.
I also work with some middle-distance runners, sprinters, and, of course, triathletes.
I mention this because I have found that muscle cramps in runners and endurance athletes seem to be somewhat universal, in that any athlete can suffer from muscle spasms and muscle cramps, regardless of their experience and fitness level.
In fact, studies suggest that muscle cramping occurs in up to 67% of triathletes.1Maquirriain, J., & Merello, M. (2007). The Athlete With Muscular Cramps: Clinical Approach. JAAOS – Journal of the American Academy of Orthopaedic Surgeons, 15(7), 425. https://journals.lww.com/jaaos/Abstract/2007/07000/The_Athlete_With_Muscular_Cramps__Clinical.7.aspx
However, certain patterns emerge in who is more prone to cramps while running and the specific types of cramps they experience.
For example, new runners seem more prone to side stitches, stomach cramps, and calf cramps while running.
In contrast, some of my experienced long-distance runners and marathon runners are more prone to experiencing leg cramps at night after races or long workouts.
Or, they might experience various exercise-associated muscle cramps only with overuse of a given muscle.
Examples include cramps in the quads after running the Boston Marathon, where there is a lot of downhill running, or a running cramp in the calves after speed work, where the runner might be spending more time on the balls of the feet.
The type of cramp a runner experiences often depends on distance, speed, terrain, and effort level.
Sprinters are more prone to acute cramps in the hamstrings and calves, particularly during high-intensity efforts where muscle fatigue sets in quickly.
Hill workouts can trigger calf or glute cramps due to the increased strain on these muscles during steep inclines.
Meanwhile, ultramarathoners frequently deal with quad cramps, especially after prolonged downhill running or elevation-heavy routes. They may also experience side stitches while fine-tuning their hydration and nutrition strategies for long endurance efforts.
While these patterns are common, they aren’t absolute—runners of any distance can experience different types of cramps based on individual factors like fitness level, fatigue, hydration, and biomechanics.
If your cramps don’t align with these typical trends, it doesn’t necessarily indicate a serious issue, but it’s worth assessing potential triggers to minimize discomfort. By understanding these patterns, we can better identify potential risk factors and implement prevention strategies to stay cramp-free.
What Causes Running Cramps?
When discussing the causes of exercise-induced muscle cramps, it is generally helpful to separate leg cramps from stomach cramps or side stitches.
While there is some overlap in the causes of leg cramps and stomach cramps, some unique factors will increase the risk of getting side stitches that won’t necessarily pertain to the common causes leg cramps.
What Causes Leg Cramps?
Historically, the prevailing theory was that dehydration and electrolyte depletion were the primary causes of leg cramps while running.2Eichner, E. R. (2007). The role of sodium in “heat cramping.” Sports Medicine (Auckland, N.Z.), 37(4-5), 368–370. https://doi.org/10.2165/00007256-200737040-00024
This is because water and sodium (salt) are lost in sweat, and electrolytes like sodium, potassium, calcium, and magnesium play key roles in muscle contraction and muscle relaxation.
Although dehydration and electrolyte imbalances may contribute to why runners get muscle cramps (particularly when doing long-distance runs or running in the heat), the association between dehydration and muscle cramps has largely been debunked.3Schwellnus, M. P. (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(4), 488–492. https://doi.org/10.1136/bjsm.2003.007021
Instead, researchers theorize that the most common cause of exercise-induced muscle cramps is due to fatigue in the muscle fibers themselves, as well as neuromuscular fatigue from the motor neurons that control the muscle fibers (motor units).4Maughan, R. J. (1986). Exercise-induced muscle cramp: a prospective biochemical study in marathon runners. Journal of Sports Sciences, 4(1), 31–34. https://doi.org/10.1080/02640418608732095
Essentially, overuse causes neuromuscular fatigue, which induces abnormal spinal reflex activity,5Maquirriain, J., & Merello, M. (2007). The Athlete With Muscular Cramps: Clinical Approach. JAAOS – Journal of the American Academy of Orthopaedic Surgeons, 15(7), 425. https://journals.lww.com/jaaos/Abstract/2007/07000/The_Athlete_With_Muscular_Cramps__Clinical.7.aspx marked by an imbalance between the excitatory impulses and inhibitory impulses to the muscles.6Miller, K. C., Stone, M. S., Huxel, K. C., & Edwards, J. E. (2010). Exercise-Associated Muscle Cramps. Sports Health: A Multidisciplinary Approach, 2(4), 279–283. https://doi.org/10.1177/1941738109357299
This causes involuntary, sustained muscle contractions because your muscles are not getting the signal to relax the contraction once it begins.7P. Schwellnus, M., Derman, E. W., & Noakes, T. D. (1997). Aetiology of skeletal muscle “cramps” during exercise: A novel hypothesis. Journal of Sports Sciences, 15(3), 277–285. https://doi.org/10.1080/026404197367281
This is known as the “altered neuromuscular control” theory of muscle cramps.8Schwellnus, M. P. (2008). Cause of Exercise Associated Muscle Cramps (EAMC) — altered neuromuscular control, dehydration or electrolyte depletion? British Journal of Sports Medicine, 43(6), 401–408. https://doi.org/10.1136/bjsm.2008.050401
Other risk factors may increase the likelihood of experiencing leg cramps running.
For example, a large study of runners found that the presence of certain underlying chronic diseases, medications, and allergies increased the risk of cramping while running, as did a history of muscle or tendon injuries, particularly in the leg muscle spasming while running.9Schwellnus, M. P., Swanevelder, S., Jordaan, E., Derman, W., & Van Rensburg, D. C. J. (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. Clinical Journal of Sport Medicine, 28(3), 289–298. https://doi.org/10.1097/jsm.0000000000000456
Most surprisingly, runners with more experience were actually found to have a greater likelihood of experiencing muscle cramps while running.
Similarly, numerous studies of Ironman athletes10Shang, 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. Clinical Journal of Sport Medicine, 21(3), 204–210. https://doi.org/10.1097/jsm.0b013e31820bcbfd have shown that the risk of muscle cramping during triathlon races increases with faster race times.11Schwellnus, 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
This is likely because muscle spasms and cramps are more likely to occur when you are exercising at a higher-than-normal intensity or above and beyond what your muscles are generally accustomed to.
Experienced runners might be able to push themselves relatively harder in races than beginners.
What Causes Side Stitches?
Side stitches, also referred to as stomach cramps, ab cramps, or side cramps are common terms for the medical condition called exercise-related transient abdominal pain (ETAP).
Up to 60% of habitual exercisers are estimated to experience abdominal cramps while exercising at one time or another.
The cause of side stitches while running or working out isn’t entirely known at this point, and in fact, there can be numerous contributing causes and risk factors.
Some of the theories about the risk factors and causes of running side stitches include the following:12Morton, D., & Callister, R. (2014). Exercise-Related Transient Abdominal Pain (ETAP). Sports Medicine, 45(1), 23–35. https://doi.org/10.1007/s40279-014-0245-z
- Ischemia or inadequate oxygen supply to the diaphragm (such as when you don’t warm up but start working out intensely or running fast).
- Increased intra-abdominal pressure.
- Stress and strain on the diaphragm muscle from uneven breathing, such as hyperventilating, rapid breathing, or holding your breath while running.
- Irritation of the parietal peritoneum, which is the lining around the abdominal organs
- Stress on the visceral ligaments that support and attach the abdominal organs to the diaphragm.
- Gastrointestinal distension (bloating in the belly).
- Low blood flow to the stomach.
- Aggravation of spinal nerves.
- Too much food in the stomach—running too soon after eating because when you exercise, blood flow is diverted away from the digestive tract to perfuse better the working muscles, heart, and lungs with oxygen-rich blood and nutrients and to help flush metabolic waste products from these tissues. As a result, digestion essentially ceases, leaving any undigested food in your stomach and intestines.
- Exercising in the heat because more blood is diverted to the skin to aid in cooling the body, leaving even less blood in the gut for digestion.
- Consuming too many energy gels, running fuel, or running hydration products (or ingesting fueling too quickly) that are too high in sugar or don’t settle well in your stomach.
- Weak core muscles.
- Poor posture when running, such as running hunched over.
- Possibly dehydration or electrolyte imbalances, particularly low sodium, potassium, magnesium, calcium, or chloride.
How Can I Prevent Cramps?
There are numerous strategies you can try to prevent running cramps:13Miller, K. C., Stone, M. S., Huxel, K. C., & Edwards, J. E. (2010). Exercise-Associated Muscle Cramps. Sports Health: A Multidisciplinary Approach, 2(4), 279–283. https://doi.org/10.1177/1941738109357299
- Always warm-up and ease into your pace gradually to give your muscles time to receive better circulation and loosen up.
- Incorporate neuromuscular training like plyometrics and targeted strength training.14Miller, K. C., Stone, M. S., Huxel, K. C., & Edwards, J. E. (2010). Exercise-Associated Muscle Cramps. Sports Health: A Multidisciplinary Approach, 2(4), 279–283. https://doi.org/10.1177/1941738109357299
- Pace yourself in races and runs, especially early on.15Schwellnus, 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. British Journal of Sports Medicine, 45(14), 1132–1136. https://doi.org/10.1136/bjsm.2010.082677
- Try to avoid shallow breathing or uneven heavy breathing while running to help prevent side stitches.
- Run with good form and upright posture.
- Make sure to wait long enough after eating to run.
- Stay properly hydrated, and make sure you consume a well-balanced, nutritious diet with natural sources of electrolytes.
Remember, if you consistently get muscle spasms or leg cramps after running, speaking with a sports medicine doctor is important. There may be other underlying causes that might fall outside of normal causes of running cramps, like overuse or muscle fatigue.
To make sure you stay well-hydrated, check out this next guide:
