The most common injury over the last 20 years in the AFL is the hamstring injury. Minor improvements in injury rates have occurred, mainly due to improved fitness training and better emphasis on injury prevention. The hamstring consists of three main muscles at the back of the thigh. There are two muscles on the inside of the thigh and the biceps femoris on the outside of the thigh. The biceps femoris is more prone to injury than the inside muscles. Hamstring injuries usually occur by an overstretching activity such as kicking or bending down to the ball or whilst the athlete is sprinting.