As group exercise classes become more and more popular, doctors have started noticing a troubling trend among their patients who engage in these oftentimes intense forms of exercise. The condition is known as rhabdomyolysis, and it most often occurs when overworked muscles begin to die and tear apart at a rapid level. The side effects include excruciating pain in the muscles and joints, as well as darker colored urine, nausea, and extreme fatigue.

Healthcare providers have started to observe that among the recent uptick in patients with rhabdomyolysis, the most common thread appears to be patients who begin new exercise routines at high intensity rates without giving their muscles time to prepare for the amount of wear and tear they will likely experience. And as the popularity of group exercise classes such as SoulCycle, P90X, and CrossFit grow, the more likely people are to experience this previously extremely rare phenomenon. Check out this recent article in The New York Times to learn more about this condition and how you can help prevent it from happening to you.