Have you ever heard of slow twitch and fast twitch muscle fibers?  Muscles that are predominantly made up of fast twitch muscle fibers are our quick reacting, higher contractile force muscles that fatigue rather quickly. Muscles made up of predominantly slow twitch muscle fibers are our less explosive muscles that are much longer lasting than their counterpart. You often hear of these two types of muscle fibers when comparing track sprinters to marathon runners. It may seem strange to think of...