Exercise-associated muscle cramps (EAMC) are defined as

cramp A cramp is a sudden, involuntary, painful skeletal muscle contraction or overshortening associated with electrical activity; while generally temporary and non-damaging, they can cause significant pain and a paralysis-like immobility of the aff ...

ing (painful muscle spasms) during or immediately following exercise. Muscle cramps during exercise are very common, even in elite athletes. EAMC are a common condition that occurs during or after exercise, often during endurance events such as a triathlon or marathon. Although EAMC are extremely common among athletes, the cause is still not fully understood because muscle cramping can occur as a result of many underlying conditions. Elite athletes experience cramping due to paces at higher intensities. The cause of exercise-associated muscle cramps is hypothesized to be due to altered neuromuscular control,

dehydration In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...

, or

electrolyte An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dis ...

depletion.

Electrolyte depletion and dehydration theory

It is widely believed that excessive sweating due to strenuous exercise can lead to muscle cramps. Deficiency of sodium and other electrolytes may lead to contracted interstitial fluid compartments, which may exacerbate the muscle cramping. According to this theory, the increased blood plasma

osmolality Molality is a measure of the number of moles of solute in a solution corresponding to 1 kg or 1000 g of solvent. This contrasts with the definition of molarity which is based on a specified volume of solution. A commonly used unit for molali ...

from sweating sodium losses causes a fluid shift from the interstitial space to the intervascular space, which causes the interstitial fluid compartment to deform and contributes to muscle hyperexcitability and risk of spontaneous muscle activity.

Neuromuscular control

The second hypothesis is altered neuromuscular control. In this hypothesis, it is suggested that cramping is due to altered neuromuscular activity. The proposed underlying cause of the altered neuromuscular control is due to

fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...

. There are several disturbances, at various levels of the central and peripheral nervous system, and the skeletal muscle that contribute to cramping. These disturbances can be described by a series of several key events. First and foremost, repetitive muscle exercise can lead to the development of fatigue due to one or more of the following: inadequate conditioning, hot and or humid environments, increased intensity, increased duration, and decreased supply of energy. Muscle fatigue itself causes increased excitatory afferent activity within the

muscle spindles Muscle spindles are stretch receptors within the body of a skeletal muscle that primarily detect changes in the length of the muscle. They convey length information to the central nervous system via afferent nerve fibers. This information can be ...

and decreased inhibitory afferent activity within the Golgi tendon. The coupling of these events leads to altered neuromuscular control from the spinal cord. A cascade of events follow the altered neuromuscular control; this includes increased alpha-

motor neuron A motor neuron (or motoneuron or efferent neuron) is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectl ...

activity in the spinal cord, which overloads the lower motor neurons, and increased muscle cell membrane activity. Thus, the resultant of this cascade is a muscle cramp.

Treatment and prevention

Medication has not been found to help reduce or prevent muscle cramping. To prevent or treat, athletes are recommended to stretch, stop movement and rest, massaging the area that is cramping, or drink fluids. Stretching helps to calm down spindles by lengthening the muscle fibers and increase firing duration to slow down the firing rate of the muscle. Recommended fluids during cramping are water or fluids that are high in electrolytes to replenish the system with sodium.

References

{{reflist Muscular disorders Symptoms and signs: musculoskeletal system Exercise physiology