seated leg curl machine
A trainer may send you to the leg curl or leg extension machine to work your legs. These two machines work the opposing sides of your thighs. Use a leg curl machine to load the muscles in the back or posterior of the leg, primarily the hamstrings. The leg extension machine has you straighten your leg against resistance and thus works the muscles on the front or anterior of the leg -- your quadriceps. Hamstrings When using either the seated or lying leg curl machine, the muscles on the back of the thigh contract to bend your knee. The hamstrings are made of three muscles: the biceps femoris, the semimembranosus and the semitendinosus. The largest of the three is the biceps femoris. Quads The quadriceps muscles are engaged when you use the leg extension machine. These muscles consist of the rectus femoris, the vastus lateralis, the vastus medialis and the vastus intermedius. During this exercise, the rectus femoris is the most-worked muscle. At the end of the motion, when your knee is almost straight, the vastus medialis then contracts. Calves The calf muscles are made of two muscles, the gastrocnemius and the soleus. But the one that is used the most during a leg curl is the gastrocnemius, which is most superficial. It crosses the back of the knee and helps the hamstrings to bend the knee when using either of the leg curl machines.