Muscle cramps in sport are a common problem in many athletes and can often stop them in their tracks. It’s both frustrating for the athlete and their coaches as it can greatly affect performance. Many reasons are behind these exercise-associated muscle cramps (EAMC) such as match fitness, inadequate glycogen stores and electrolyte imbalance, however there are two distinct categories that need to be understood when it comes to EAMC.
First skeletal muscle overload and fatigue from overuse or insufficient conditioning can cause localized cramping in the overworked muscle fibers. Secondly in contrast, heavy sweating resulting in fluid loss and whole-body sodium deficit can lead to more widespread muscle cramping even when there is minimal or no evidence of muscle overload and fatigue.
Both categories of cramping, exercise-associated (overload and fatigue) and exertional heat cramps (sweat induced sodium deficit) need to be specifically clarified when talking to health care providers, coaches and athletes to not only achieve a better understanding but also to select the most effective treatment and prevention strategies.
Furthermore, there is some confusion with exertional heat cramps in that a hot environment is not a necessary prerequisite and many athletes encounter muscle cramps in cool environments or even indoors. Excessive core temperature is also not an underlying determinant.
Exercise-Induced Muscle Cramps (overload & fatigue):
Repeated or extended loading on selected muscle groups can lead to muscle or tendon strain and local fatigue during sports competition and training in a variety of sports and physical activities. The muscle fatigue hypothesis suggests that the intramuscular mechanisms (specialized receptors) designed to inhibit muscle contraction in response to muscle tension are disrupted or depressed. Predisposing risk factors associated with overload and fatigue-related muscle cramping may include poor stretching habits, insufficient conditioning and excessive exercise intensity and duration to name a few. Distinguishably, such muscle cramping remains localized to the overloaded and fatigued muscle group (such as with the calf muscles), that can sometimes spread slowly across the involved muscle region.
Exertional Heat Cramps (sweat-induced sodium deficit):
With exertional heat cramps, an athlete typically would have been sweating extensively with appreciable sweat electrolyte losses as well, in particular sodium and chloride. Often, sodium deficit progressively develops over several days of repeated sweat electrolyte losses that often exceed dietary salt intake. The cause of exertional heat cramps extends down to the cellular level in which the interstitial compartment remains contracted. As a result, axon terminals of selected motor neurons can be mechanically deformed, and surrounding extracellular ion and neurotransmitter levels can increase. This leads to hyper-excitability of the nerve terminals which can initiate action potentials in the affected muscles causing them to twitch and fasciculate uncontrollably which inevitably evolves into heat cramps if not identified and treated quickly. Exertional heat cramps are usually more widespread affecting (often bilaterally) a number of different muscle groups (e.g. quads and/or hamstrings in both legs) and profuse, repeated, or moderate long-term sweating appears to be the primary factor.
My tips are to make sure you're well fuelled, and hydrated before exercise. For a more personalised plan you may like to consult with an Accredited Sports Dietitian who can work out your sweat rate and determine how much salts you lose (via sweat patch) to tailor an individual plan for you to prevent muscle cramps. To find a sports dietitian head to www.sportsdietitians.com.au
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