The seated or lying leg curl machine is popular for isolating some of the major muscles in the lower body and you’ll see the exercise being performed in almost any gym. So what muscles do leg curls work?
Muscles directly worked – hamstrings
Muscles indirectly worked – quadriceps, calves
Obviously, the legs are the primary target of the seated or lying leg press exercise. The hamstrings are the primary muscle group worked with this machine.
The hamstrings are the group of muscles located on the back of your thighs, underneath the glutes and above the knee. It consists of 3 muscles – the semitendinosus, semimembranosus, and biceps femoris.
The setup of most machines are designed to isolate the hamstrings, and they are certainly the primary mover during the exercise. However, other muscles are also indirectly worked. The quads and the calves, in particular, are responsible for stabilizing the leg during the movement.
While all leg curl machines are designed to hit the hamstrings, varying the setup can change the way the target muscles are hit. Similar to leg extensions, your stance can influence how the muscles are worked. Spreading your legs farther apart will target the inner parts of you hamstrings, while putting your feet closer together will work the outer parts.
There are 2 main types of leg curl machines – seated or lying. They target the muscles very similarly, the only difference is your body position. In the seated version, you are obviously sitting and pull the weight under you. In the lying version, you lay face down on the bench and pull the weight towards your glutes.
The video below demonstrates the seated version. If you are new to this version, it may be a little tricky at first. Your legs go between the lower pad, which goes under your achilles, and the upper bad, which locks on to your quads. With the way your legs are locked into place on this machine, you are forced to use your hamstrings to do the work, which is the point of the exercise.
The next video demonstrates proper technique for the lying version. With this version, your body is locked between the bench and the resistance pad. This version allows some people to cheat on their reps by rocking their upper body on the movement, but it is important to use solid technique and focus on the muscles you are supposed to be using.
Leg curls are hardly the only exercise that targets the hamstrings. Although, the basic makeup of the machine allows you to isolate them to add size and strength better than maybe anything else.
If you are working your legs for performance reasons, there may be some better lifts you can do that are more functional. There are plenty of variations of squats, deadlifts and lunges that work the same muscles but also give benefits to your core and other body parts. The leg curl machine can still be used as a supplement to your lower body training.