I think the answer is stretching. It is good to stretch the muscles before you do a intense workout. You must prepare your muscles and get it started. Do the workout easy and slowly for your body to get use to then once you have enough energy then kick up to either medium to hard to intense workout.
Specificity is the answer. You are targeting a certain muscle in your body to improve it for an upcoming sport or activity like running a marathon or entering a Mr.Olympian body-building competition.