The hamstrings, or as they are sometimes referred to the “hammies”, are the muscles that run down the back of your leg and flex your knee. Unfortunately hamstring injury is extremely common. It affects people across all sports and, more often than not, they are really tricky to deal with. Most people tear a hamstring when performing explosive activities like sprinting, changing direction, rapidly slowing down, and kicking. Your hamstring can also tear from slower speed movements if done in the right way.