CrossFit is a dangerous workout for anyone who does it. In fact, in a 2014 study from the University of Rochester School of Medicine and Dentistry, researchers surveyed 386 CrossFit participants and found that 75 of them had been injured while doing CrossFit?that's a 20 percent injury rate! Seeing as older bodies take longer to recover, anyone over 40 should especially think twice before signing up for CrossFit.