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Exercise Associated Musle Cramps - Causes, Treatment & Prevention (2)

EAMC are are a common experienced condition experienced by athletes in every sport. There´s currently no scientific prove for the cause that is widely accepted. Theories for the cause relate to observational studies rather than sound experimental scientific evidence. That´s why treatment methods vary in terms of their effect and prevention strategies remain on luck which makes it hard to find the ultimate prevention strategies and it´s also a reason why these strategies remain unsuccessful.

As we looked on dehydration as a potential cause in the first article we´ll focus on heat as an influential factor and the science behind it.

 

If it´s not the fluid loss through heat, is it perhaps the heat itself that leads to the muscle cramps? The scientists are also following this trail. And indeed a picture emerges here: Many athletes complain of spasms, especially in competitions under hot and humid conditions. Martin Schwellnus of the University of Cape Town states the following:

 

"It is well documented that there are a number of mechanisms by which exercise in the heat will result in the development of muscle fatigue, independent of electrolyte depletion or dehydration."

 

The experienced heat stress is even more pronounced during exercise because the body is producing more heat itself. Therefore, the thermoregulatory system of the human body has to speed up heat dissipation mechanisms. The first response of the body to heat stress is increased vasolidation in the skin and the second is sweating. Vasodilation causes a transport of the heat from the core to the skin. As a result, more blood will go to the skin, the stroke volume drops and the heart rate increases to maintain the cardiac output. In addition, sweat glands are stimulated to allow cooling by evaporation.
Muscle fatigue is defined as an exercise-induced reduction in the ability of a muscle to generate force or power.
A high environmental temperature can cause higher muscle temperaturesAs the temperature around the muscle fibres increases, the temporal characteristics of contraction and relaxation are changed.

 

In conclusion, heat has an influence on the neuromuscular control of the peripheral and central nervous system but this does not result in a greater occurrence of EAMC. However, more EAMC will occur due to increasing muscle fatigue, which causes a change in neuromuscular control due to a hot outside temperature.

 

The first suggested prevention method for cramps is the consumption of salt and fluid. People working in an industrial setting in a high temperature were given a saline solution orally and this prevented cramps to occur. This same prevention strategy is applied during tennis in the heat and it is recommended by the National Athletic Trainers’ Association to be well hydrated before exercise to avoid cramps. However a recent study shows that the total amount and rate of sodium intake during an ultramarathon in a hot environment is not related to muscle cramping, dehydration or hyponatremia.

To prevent EAMC it may be better to prevent muscle fatigue and altered neuromuscular control. Muscle fatigue can be
prevented by training and/or by reducing work intensity and duration. It is well-known that physical training on
the long term can reduce the accumulation of waste products within the muscle and thereby offset muscle fatigue.
Thereby an increased (muscle) fitness level can prevent EAMC. The altered neuromuscular control may be prevented
by interventions that target muscle spindle and Golgi tendon organ receptors. This will delay the occurrence of neuromuscular fatigue and thus EAMC.
Static stretching pre-exercise was proposed as such an intervention. However the increased Golgi tendon inhibition is not still present 30 minutes after the static stretching and therefore unlikely to have an preventive effect. Plyometric exercises appear to be more successful, by improving the efficiency and sensitivity of reflexive and descending pathways used for neuromuscular control.

 

Refernces
Gandevia SC. Spinal and supraspinal factors in human muscle fatigue. Physiol Rev. 2001;81(4):1725-89.
Parkin JM, Carey MF, Zhao S, Febbraio MA. Effect of ambient temperature on human skeletal muscle metabolism during fatiguing submaximal exercise. J Appl Physiol. 1999;86(3):902-8.
Close R, Hoh JFY. Influence of temperature on isometric contractions of rat skeletal muscles. Nature. 1968;217(5134):1179-80.
Ranatunga KW. Temperature-dependence of shortening velocity and rate of isometric tension development in rat skeletal-muscle. J Physiol. 1982;329(AUG):465-83.
Segal SS, Faulkner JA. Temperature-dependent physiological stability of rat skeletal-muscle invitro. Am J Physiol.  1985;248(3):C265-C70

Bergeron M. Muscle cramps during exercise: is it fatigue or electrolyte deficit? Curr Sports Med Rep. 2008;7:S50-S55

 

Binkley H, Beckett J, Casa D, Kleiner D, Plummer P. National Athletic Trainers’ Association position statement: exertional heat illnesses. J Athl Train. 2002;37:329-343

 

Kantarowski P, Hiller W, Garrett W. Cramping studies in 2600 endurance athletes. Med Sci Sports Exerc. 1990;22:S104

 

Khan S, Burne J. Reflex inhibition of normal cramp following electrical stimulation of the muscle tendon. J Neurophysiol. 2007;98:1102-1107

 

Ramsey F, Schafer D. Drawing statistical conclusions. In: The Statistical Sleuth: A Course in Data Analysis Methods. 2nd ed Pacific Grove, CA: Duxbury; 2002:1-27

 

Schwellnus M. Cause of exercise associated muscle cramps (EAMC)-Altered neuromuscular control, dehydration, or electrolyte depletion? Br J Sports Med. 2009;43:401-408

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