CrossFit is a popular fitness trend popping up in both neighborhood gyms and trendy metropolitan locations across the country (and around the world). Since its launch in 2000, CrossFit programming is now used in over 7,000 affiliate locations around the world. Along with its rising popularity is the concern for an increased incidence of a condition called “rhabdomyolysis”, muscle damage and potential acute kidney failure due to extreme exercise.
CrossFit programs are “constantly varied, functional movements, done at high intensity”, with the goal of improving one’s fitness. A CrossFit workout can be described as a combination of aerobic exercise, bodyweight training, gymnastics movements, and Olympic lifting in a time-efficient way that is designed to take someone to their physical limits.
Prior to the emergence of CrossFit in the year 2000, rhabdomyolysis was, for the most part, was primarily seen as a result of high intensity physical efforts like military training or other very demanding situations in high temperatures (police academy, firefighter training, football training). In recent years, this condition has also been documented in those exercising at the gym. According to studies conducted by the Centers for Disease Control and Prevention in the late 1980s, there are approximately 25,000 cases of rhabdomyolysis each year in America (almost 50% of these cases are due to exercise). More recent studies have not been published by the CDC.
According to WebMD, rhabdomyolysis:
… is a serious syndrome due to a direct or indirect muscle injury. It results from a breakdown of muscle fibers and release of their contents into the bloodstream. This can lead to complications such as kidney (renal) failure. This occurs when the kidneys cannot remove waste and concentrated urine. In rare cases, rhabdomyolysis can even cause death. However, prompt treatment often brings a good outcome. Here’s what you need to know about rhabdomyolysis.
Muscle Development, Muscle Damage and Rhabdomyolysis
A degree of muscle damage during exercise is completely normal, and in fact required for muscle building. When muscles are used, they are damaged and then rebuilt by the body to adapt to a greater workload. For example, 24 to 48 hours after a hard workout the muscles experience soreness (aka. delayed onset muscle soreness – DOMS). This feeling of soreness is a sign of muscle damage (the normal variety). This means the muscles are being rebuilt to be stronger and better in an attempt to adapt to the stress you subjected them to in the weight room.
If the muscle damage is too extensive, which can happen in extreme rhabdomyolysis, the results can be dangerous. When the muscle cells are broken down, myoglobin (a protein found in the muscle tissue that extracts oxygen from blood help the muscle perform work) leaks out from inside the cell. The abundance of myoglobin in the bloodstream, as seen with rhabdomyolysis, must be filtered by the kidneys, which are not well-equipped to process the influx of protein. In potentially lethal cases of rhabdomyolysis, acute kidney failure (the rapid loss of the kidneys’ ability to remove waste and help balance fluids and electrolytes in the body) can occur. This can occur within two days.
How to Prevent Exertional Rhabdomyolysis
Short of knowing that you have a genetic condition that may increase your risk, here are several training tips that should substantially reduce the risk of rhabdomyolysis.
- Progress gradually in your workout program according to your existing fitness, whether it’s cardio, circuit or weights.
- Monitor your fluid intake, particularly when your workout is long, intense or hot, especially all three together. But don’t go overboard; more fluid is not necessarily better.
- Don’t exercise hard on low-calorie diets or after long fasting periods. Ensure you have sufficient fuel on board to allow your muscles to work efficiently. Be careful of low-carb diets mixed with hard and long exercise.
- Limit recreational drugs like alcohol before exercise, and don’t take illicit recreational or performance-enhancing drugs. Be cautious of genuine over-the-counter needs like anti-inflammatory drugs and check with your doctor about prescription drugs. Most will probably be okay.
Articles on Rhabdomyolysis
Below are links to additional information on exertional rhabdomyolysis:
- Exertional Rhabdomyolysis and Acute Renal Impairment (Centers for Disease Control and Prevention)
- Exertional Rhabdomyolysis: Case Study of an Athlete (National Strength and Conditioning Association)
- Exertional Rhabdomyolysis – Uniformed Services University of the Health Sciences
- The Truth About Rhabdo (The CrossFit Journal)
- CrossFit Induced Rhabdo (The CrossFit Journal)
- What is Rhabdomyolysis? (Navy Medicine)
- Rhabdomyolysis: When Muscle Breaks Down (CSU Chico)
- CrossFit’s Dirty Little Secret (PTThinkTank.com)