Vigorous exercise is associated with improved quantity and quality of life. With vigorous exercise, however, comes the risk of injury. This article reviews the current highlights in our understanding of muscle injuries during various activities diagnosed by MRI. In particular, after general remarks on indirect ''strain'' muscle injuries, we focus on specific muscle injuries in the thigh (hamstrings and rectus femoris), chest wall region (pectoralis major, latissimus dorsi, and teres major), and abdominal core (internal and external oblique muscles).