Exertional rhabdomyolysis results from the degeneration of skeletal muscle often caused by excessive exercise (1,2). When skeletal muscle membranes are damaged, their intracellular contents enter the bloodstream and can cause potentially serious side effects and even death (3,4). Symptoms include muscle pain, stiffness, fatigue, dark colored urine, electrolyte imbalance, and possible renal (kidney) failure (2,3). Additionally, moderate-intensity exercise (55% to 90% of HRmax) may elevate creatine kinase (CK) to levels that meet the diagnostic criteria for rhabdomyolysis, especially if the exercises involve eccentric muscle contractions (5). Studies show that increasing the intensity of an activity (e.g., lifting higher loads, anaerobic sprinting events) results in higher creatine kinase levels when compared with lower intensity longer duration activities (moderate loads, aerobic endurance events) (2-4).
High Risk Individuals
The incidence of rhabdomyolysis is difficult to determine and most likely underreported. Individuals at risk for rhabdomyolysis are often de-conditioned and just starting an exercise routine, or are participating in high intensity exercise in hot and humid climates (3,9).
Most reported cases of exertional rhabdomyolysis involve military personnel or law enforcement and fire department trainees (4,7,8). Data from these groups are considered to be reliable because both groups participate in similar strenuous activities with medical supervision.
Collegiate football players participating in pre-season, two-a-day practices in hot and humid weather are also at risk for heat illness and rhabdomyolysis (6). In fact, sweat rates in large lineman can reach 3.9 liters per hour and up to 14 liters per day (6). Due to high intensity activity and abundant fluid loss, football players run a high risk of dehydration and subsequent exertional rhabdomyolysis.
There are several precautionary methods that coaches, drill instructors, athletic trainers, and sports performance specialists must observe to help prevent exertional rhabdomyolysis. When football players, military, fire or police personnel are exercising in extreme heat and humidity, the two most important preventative measures include proper hydration and proper rest and recovery periods.
Additional preventative measures that should be considered include training in the cooler early morning and evening hours, utilizing a sports drink rather than just plain water to replace electrolytes, monitoring an individual’s body weight before and after training sessions for fluid loss, educating individuals to recognize risk factors such as dark colored urine, muscle stiffness and pain, and holding training sessions without requiring athletes and service personnel to wear full gear such as shoulder pads, helmets, fire gear or back packs.
Individuals at risk for rhabdomyolysis are often out of shape and just starting an exercise routine (3). Thus service personnel and athletes must have substantial aerobic conditioning. Make sure exercise training sessions do not exceed the current aerobic capabilities of the participants involved. The last step to ensure adequate preparation is by optimizing the individual’s diet plan, including the consumption of adequate amounts of carbohydrates, fats, proteins and water prior to training sessions. Moreover, during the training sessions, individuals will need to consume plenty of fluids to avoid dehydration.
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