Injuries have kept Hall out of his last few high-profile events, including last August's Olympics and last fall's New York City Marathon. Each injury requires its own particular treatment, he notes. An opposite-side quad injury last fall was much more serious than the latest one. For that, he says, he needed five full weeks off and was reluctant to cross-train during that time, since "pretty much everything – biking, elliptical – involves the quad. "Sometimes people drag out injuries by cross-training too aggressively," he says. "They could have healed much more quickly." On the other hand, he missed the Olympics due to tendinitis in his right hamstring, an injury that he says can worsen if it's rested too much. He treated that with strength training and some aggressive, "very painful" shockwave therapy in Phoenix with his physical therapist, John Ball.

Prior to the hamstring trouble, Hall dealt with an excruciating case of plantar fasciitis – "probably the worst injury I have ever had in terms of pain and how long it takes to get over it," he says. His case lasted about eight months: He tried every trick in the book, from night splints and exercises to stretching and shockwave therapy. In this case, rest was not a good idea, either. "I took three weeks completely off, and when I came back, it was probably worse," he recalls. "The best advice I got came from an old-timer at a clinic who told me, 'The bad news is it's going to hurt, but the good news is it is going to get better.'"