Muscle Cramping – More than Dehydration


Gotta love academics! They define what we athletes know as a cramp this way: an exercise-induced muscle cramp is ‘a painful, spasmodic, involuntary contraction of skeletal muscle during or immediatley after exercise’. Research scientists have shown that the prevalance of cramping is as high as 37% in athletes. This review will highlight that the old theories of electrolyte imbalance as the cause of cramping are now being questioned. More importantly, we’ll use modern theories on cramping to highlight how to minimise their occurence during and after training or racing.

What are the Risk Factors?

Historically, numerous causes and thus risk factors have been implicated in cramping. These include:

  1. Accumulation of by-products of muscle metabolism that impair muscle contraction (e.g. lactic acid)
  2. Depletion of electrolytes such as sodium and potassium
  3. Loss of fluids and thus dehydration
  4. Extreme environmental conditions of heat and cold
  5. Lack of blood supply

However, while these are risk factors, previous and ongoing current research suggests they are not the causes of muscle cramps. Other factors have also been shown to increase the prevalence of cramping. These include:

  1. Having a history of cramping
  2. Competing at a faster pace than training pace
  3. Doing too much static (holding) stretching before racing
  4. Increased race duration and thus fatigue
  5. Not tapering enough before the race
  6. Racing with prior muscle fatigue or damage
  7. Muscles that cross two joints (e.g. hamstrings, quadriceps and gastrocnemius in the calf)
  8. Having a lower threshold frequency for cramping (15 Hz-cycles per second) than non-cramping people who have a threshold frequency of 25 Hz. This threshold frequency is the minimum frequency needed to stimulate a cramp. This thus suggests the nervous system is involved in some way.

What are the Theories?

The physiology of muscle contraction and relaxation may help explain the current theories. Three critical things need to occur for muscle contraction and relaxation. First, energy is needed for the muscle to contract and then relax. To do this, calcium in the muscles that stimulates the contraction must also be reabsorbed into pockets in the muscle so that the contaction stops. Dysfunction of either of these processes (calcium release and calcium reabsorption) can mean permanent contraction and thus contraction. Fatigue during exercise can cause this resorption of calcium to occur poorly. Thirdly, the electrical activity in the muscle must also be normal. If not, the muscle may be continually stimulated and thus contract and stay contracted. If any of the pathways that create this electrical activity are upset, the muscle may stay contracted. Again, fatigue can cause the muscle’s electrical activity to be upset.

In all the available literature, it appears that fatigue either within the muscle or within the nervous system itself may be related to cramping.

Treatment and Prevention?

Taken together, the above theories plus years of anecdotal evidence suggest the following ways to prevent cramping in athletes:

  • Carbohydrate and electrolyte supplements before ans during exercise may extend the time to fatigue and thus onset of cramping
  • Hydration before and during racing
  • Ensure you taper to reduce fatigue levels going into the race
  • Train at race pace leading into the event
  • Don’t overdo static stretching before the race, use dynamic stretching instead

If you get a cramp do passive stretching and consume fluids and electrolytes to alleviate the cramp the fastest.

Sources: 1. Buskard, A. (2014). Cramping in sports: Beyond dehydration. Strength and Conditioning Journal, 36(5): 44-52. 2. Minetto and others (2013). Origin and development of muscle cramps. Exercise and Sport Science Reviews, 41: 3-10. 3. Schwellnus, M. (2009).  Cause of exercise associated muscle cramps (EAMC)–altered neuromuscular control, dehydration or electrolyte depletion? British Journal of Sports Medicine, 43(6): 401-408.