A runner reading about a dangerous side-effect of high-intensity training wonders what her risks are.
Ali asks: I’ve been reading recently about a terrible side effect of overtraining called ‘rhabdomyolysis’ or ‘rhabdo’. Apparently it’s been happening to people in spin classes and other high-intensity workouts. As a runner, what’s the likelihood that something like this could happen to me? I love working out hard, and don’t want to give up my high-intensity interval training. Are there any warning signs so I can know if I’m in danger?
This is a great question and very timely! Rhabdomyolysis is the name for when muscle cell contents leak into the bloodstream. Doctors can ID rhabdomyolysis by looking at levels of creatine kinase (CK) in the blood.
Almost anyone who works out to improve performance will release or leak some CK into the blood stream, and athletes with large muscle mass, like rugby players, may have baseline CK levels that are above the generally accepted normal range.
But this becomes a problem when the muscle cell releases contents like potassium and myoglobin, causing medical complications. This stuff passes through the kidneys, where ideally it would be filtered out. But too much myoglobin, which is a protein similar to haemoglobin, can damage the kidney, resulting in kidney failure.
The release of muscle content into the bloodstream can also interfere with blood clotting, and can produce spontaneous bleeding.
There are several common causes of rhabdomyolysis, including medications (statins, SSRIs, diuretics), heat stroke, or any injury where the body is crushed (such as a car crash). But the one you’re worried about is intense exercise.
Often you hear about a football team where the strength coach has pushed the players too hard for too long, or a spin class where an instructor takes a workout beyond the group’s limit. Occasionally, there are case reports of an individual who sets stretch goals for push-ups or squats and develops rhabdomyolysis from overworking a set of muscles.
It is a bad idea for anyone to surprise muscles with an unexpected volume of work that is well beyond the usual level (which is one of the reasons for the 10 percent rule), since rhabdomyolysis can lead to renal failure and even death from arrhythmia.
Could this happen to you as a runner? Yes, it’s technically possible, but the likelihood that you would develop rhabdomyolysis is slim unless you are drastically increasing your training volume or intensity, which can cause all kinds of overuse injuries.
If your typical workout is ten 400 metre sprints and you increase it to 20 or 30 repetitions, you are setting yourself up for this type of muscle damage. The key to safe high-intensity interval training is gradual increases in volume and difficulty to allow your muscles to adapt to the loads over time.
As for warning signs, muscle soreness that does not go away (when the muscle pain goes beyond the usual pain of a workout) can be a clue you are pushing too hard. One sign to look for is your urine becoming a dark cola color.
Muscle swelling also occurs with cell breakdown and can lead to compartment syndrome as muscle tissue swells within the fascia compartments of affected muscle groups. If you think you have rhabdomyolysis get to the ER immediately – it is a medical emergency and requires treatment with intravenous fluids and sometimes dialysis to filter out the destructive muscle contents from the blood.
Prevention requires you to understand your body and your exercise capacity. The person at greatest risk is often the one who is aiming for an ill-conceived numerical goal or making an extra effort to keep up with the pack. Not pushing too far beyond your current baseline and quitting too early will offer protection.