A leg curl machine is a piece of exercise equipment that isolates the hamstrings. It consists of a bench that the athlete lies on, face down, and a padded bar that fits over the athlete's heels. This bar provides resistance as the athlete bends the knees, thus curling the legs and driving the feet toward the buttocks. A lot of leg curl machines also have an additional bar that enables the user to perform leg extensions as well. Sometimes an athlete will use a leg curl machine to work each leg individually, and sometimes he or she will work both legs at the same time.
The largest part of a leg curl machine is the bench. When the athlete lies on it, his or her legs should hang off the end of the bench just above the knees. The bench is padded and often will have some kind of handles on the underside that the athlete can hold while performing the exercise. These handles provide stability and ensure that the athlete doesn't rock from side to side when using the machine.
The other important part of a leg curl machine is the bar, which attaches to one end of bench at a single movable joint. Sometimes this bar has an extension that allows the athlete to place weights directly onto it. Other leg curl machines use a chord and a system of pulleys to attach the bar to a set of weight plates that an athlete can adjust using a pin. Either way, the bar is padded and extends far enough away from the bench that when an athlete is in the proper position and lying with the legs straight, the bar will rest on the back of the calves just above the heel.
In order to perform a leg curl, the athlete takes the proper position and then tenses the hamstrings in order to bend the knees. Doing so will bring the feet toward the buttocks. If a leg curl machine has handles, the athlete should hold onto them or, if it does not, should hug the bench to provide the necessary stability. Also, the athlete must ensure that his or her body remains flat against the bench without raising the buttocks or thighs off the bench. Once the legs have bent as far as possible, the athlete lowers the weight back to the original position.