A study out of the University of Missouri that found that guys with a "man- of-steel," "I-can-do-anything" attitude tend to heal faster than other guys.
This is most likely because macho guys tend to believe in working hard to overcome obstacles, and reaching their goals, especially when it comes to something physical like rehabbing an injury.
However, men of steel also tend to engage in the kinds of behavior that puts them at risk for injury, like riding motorcycles, and playing extreme sports. Plus, macho men also tend to resist psychological counseling, so dealing with the emotional part of rehabbing an injury can be harder.