Rhabdomyolysis, or rhabdo for short, is a condition caused by damage to skeletal muscle. There are several causes of rhabdo but the main ones pertaining to endurance athletes include exercise (especially if poorly hydrated), crush injuries(which can occur due to any accident where muscle tissue is damaged, think bike accident), heat stroke, hyperthermia(elevated body temperature), and hypokalemia (low potassium due to losses during exercise or other causes).
Rhabdo can be a serious and even life-threatening condition. It can lead to acute kidney failure, electrolyte abnormalities(like hyperkalemia and hypocalcemia which can lead to life-threatening cardiac arrhythmias), disseminated intravascular coagulation(DIC, a condition leading to formation of blood clots in the small blood vessels throughout the body causing compromise of blood flow to tissues and ultimately leading to damage of multiple organs and eventually to a severe bleeding disorder after clotting factors and cells involved with clotting are used up), and compartment syndrome(a painful condition due to an increased pressure around the muscles that can compromise blood flow to nerves, muscle and other tissues in the affected limb leading to permanent muscle or nerve damage).
The symptoms of rhabdo include muscle pain(usually severe pain after exercise, not just the typical muscle aches from working out), muscle swelling, generalized weakness, specific localized muscle weakness, nausea and vomiting, dark “tea” colored urine and confusion. Not all of these have to be present to have rhabdo. If you have any of these symptoms, seek medical care as soon as possible.
Preventing rhabdo is not always possible however you can lessen your chances of getting it by staying well hydrated while exercising/racing. Drinking fluids that will replete your fluids and electrolytes (especially sodium and potassium) lost during exercise cannot be overemphasized. While drinking plain water might restore fluid lost, it will not replete the electrolytes lost and can lead to several complications including hyponatremia (low sodium).
Rhabdo is easy to diagnose by medical professionals and requires some simple blood tests. The treatment is also easy and mainly consists of intravenous fluids infused at a high rate.
The bottom line: If you have completed heavy exercise, especially after going hard during a race, and you have severe muscle pain above what you typically experience after a workout or if you have any of the other symptoms listed above, seek medical care. A quick and simple examination and blood test can diagnose or rule out rhabdo and be life saving.