There are two main problems with injuries. The first is the injury itself. The body will heal on its own. It is very good at healing when given the chance. The second problem is the bodies reaction or compensation to the injury. This is the bigger of the two problems. In fact, even after the injury heals, the compensation is still in place and actually gets "locked in". The accepted idea of REST does not work to have this compensation free up. This is why rest won't necessarily have one recover from a soft tissue injury.