The hamstring muscles are located in the back of the thigh. There are three different muscles that comprise the group of muscles called the hamstring muscles. This group of muscles so called because if they are cut the person is essentially ‘hamstrung’ or unable to walk.
The three muscles are the biceps femoris, semitendonous and semimembranosus and are attached at the bony prominence in the buttocks and the back of the knee. They are responsible for the power behind each running or walking stride. Many sprinters have well developed hamstrings and quadriceps (muscles on the front of the thighs) to provide explosive power out of the blocks.
A hamstring injury happens when the runner isn’t well warmed up, stretches too vigorously or as a result of chronic stress. As a result the runner will have pain when the knee bends and the thigh moves backwards relative to the trunk of the body.