u just need to train your muscles to handle the load u put on them, to do this you need to do a combination of short sprints and longer runs (at a good speed)....but the key factor is to train 3-4 times a week and stick to it, maybe run 2 days and hit the gym 2 days, it takes time to build muscle and the biggest problem people have is they stop training after not getting the results they want right away, the results will come, if u put the time and effort in (and maintain that effort even after u reach your goals).