Just as the overlying skin hides skeletal muscle from direct assessment in clinical evaluation of muscle disease, so does it hamper studies that probe basic mechanisms underlying muscle use in exercise science. As a test of organ function, magnetic resonance imaging (MRI) of muscle activation expanded the breadth and type of information available to scientists by allowing the noninvasive dissection of muscle activity, merging functional and morphologic information that link directly to classical tests of muscle performance. Extending to sequellae of overexertion, from the self-limited condition of sore muscles that all of us experience to the more burdensome problems of acute muscle injuries and complications, MRI continues to develop as an important tool to unveil hidden mysteries that underlie and limit locomotion. This article reviews a substantial body of data accumulated over the last 10 years in these interesting, albeit slightly unconventional, applications.