Exercise-associated muscle cramps, or EAMC, is a temporary, intense, painful and involuntary contraction of skeletal muscles.
These commons contractions usually take place during or soon after physical activity. Some studies have evaluated that EAMC affect up to two thirds of triathletes, 18-70% marathoners and 30-53% football players.
For many athletes cramping is a minor incident of rare occurrence, but for others, maybe less than one every thousand runners, it can be a serious problem because of its frequency and/or intensity. In severe cases the pain may last even for days after the acute contraction has finished.
Some risk factors have been pointed out, although there are contradictory results:
- Endurance activities and team sports.
- Presence of fatigue and running at a faster than training pace.
- Older age and long running history.
- Irregular stretching
- High BMI and familiar history.
The mechanisms behind cramping are yet unknown, although there are two different theories trying to explain them:
- a disturbance of electrolytes balance.
- an abnormal discharge of motor drive to the muscles.
Alteration of hydration and electrolyte balance
The main evidence supporting this theory comes from large studies of industrial workers during the 1920s and 1930s. Cramps were usually observed in fatigued workers, especially in those less physically fit at the end of their shifts.
Large losses of electrolytes in sweat combined with an excessive intake of plain water could be the main reason behind cramping. The administration of saline drinks or salt tables reduced greatly their incidence.
Nevertheless, recent studies have found no difference in the electrolytes concentration in plasma with cramping episodes, but blood samples were usually taken “after” the incident, and not exactly “during” the episode.
Although cramping happened more often in hot weather conditions, it happens also in cool environments almost without sweating. Therefore, the theory of electrolyte imbalance would be inadequate to describe all EAMC.
Alteration of neuromuscular control
Fatigue increases excitatory neuronal signals to muscles, while at the same time decreases inhibitory signals from tendons to the muscles. Combination of both effects causes the cramp, or uncontrolled contraction.
Stretching of muscles during a cramp episode is known to alleviate the symptoms. It is thought that with passive stretching of the tendon, it can inhibit again the muscle reflex.
Athletes more prone to EAMC had lower thresholds for electrically activating motor nerves.
Prevention and treatment
As we mentioned previously ingestion of saline solutions could be the most effective prevention tool for muscle cramping.
Besides it, quinine has also been studied, although it may carry adverse effects too. Ingestion of 200-500mg quinine per day reduced cramp frequency and intensity but had no effect on duration.
When cramping is induced electrically in humans, it was found that pickle juice, with a high salt content and sharp taste, reduced cramps duration by 37% (1mL after 2s of cramping) without altering blood electrolytes concentration.
Ingestion of spicy foods such chilli or ginger has effects on the receptors in the mouth, but it is obvious that they also induce a variety of physiological responses. It could be possible that they induce physiological signals capable of disrupting electrically the spontaneous muscle cramps.
Regarding EAMC treatment, passive stretching could be the way to go, although it is difficult to evaluate its utility as cramps episodes usually resolve spontaneously.
- EAMC is a common phenomenon in sports and exercise activities.
- Highly unpredictable, intensity and duration vary greatly.
- More often associated with high temperature and sweating, although it also takes place in cool conditions.
- There may be different mechanisms to explain the cramps in different situations.
- Prevention and treatment strategies are not yet fully understood.
We hope to have brought you some light on the subject.
Muscle Cramping During Exercise: Causes, Solutions, and Questions Remaining.
Maughan RJ, Shirreffs SM.
Sports Med. 2019 Dec;49(Suppl 2):115-124. doi: 10.1007/s40279-019-01162-1.