A Massachusetts woman almost lost her leg after she developed a medical condition from a single spin class.

After taking the class, Kaelyn Franco, 23, developed a serious medical condition called rhabdomyolysis that left her with severe pain and swelling, according to Today. Franco ended up having to go through emergency surgery in order to save her leg after developing the condition, wherein damaged muscle tissue releases proteins or electrolytes into the bloodstream, according to the Centers for Disease Control and Prevention.