Considering his leg was broken, he ran a pretty good time In the 2012 London Olympics, Manteo Mitchell broke a bone in his leg while running in the 4 × 400 meter relay—yet he still finished. In fact, he ran an excellent time. How’d he do that? Although Mitchell experienced pain, he experienced less pain than would a sedentary person whose leg was broken. During intense exercise, the body’s endogenous opioid system blunts the conscious experience of pain.