Spin classes are very popular these days, but if you're not careful they could leave you with health issues. A new study published in the American Journal of Medicine reveals first-time spinners, especially those taking high-intensity spin classes, have a chance of developing rhabdomyolysis, a serious syndrome caused by muscle injury. Rhabdomyolysis occurs when severe muscle trauma, due to a lack of oxygen, causes muscles to break down and release their contents into the bloodstream-- which can lead to serious complications, including kidney failure. The condition is typically found in victims of a crush injury, such as a building collapse, fall, or car crash, but now doctors are seeing it as a direct result of spin classes. For about half of the people who develop the condition, it will fix itself. But for those whose muscles have suffered severe damage, symptoms of a more serious problem include dark urine, severe muscle aches, nausea and a feeling of weakness. To avoid the condition you should "take it slow" when starting a new exercise regimen. The Independent