The leg extension is an exercise that is usually performed with a leg extension machine. You sit on a soft chair and lift the bar with your feet. This exercise primarily works the quadriceps muscles in the thighs – the rectus femoris and the vastus muscles. Technically, this is an “open-chain kinetic” exercise, which is different from a “closed chain kinetic exercise,” such as the squat. The difference is that in squatting, the part of the body that you are training is anchored (the foot is on the ground), while in the extension leg, you are moving the padded bar, which means your legs are not stationary while they are working, and thus the chain of motion opens in the leg extension.
The Pros and Cons of Leg Extension Machines
Pro fitness haven debated leg extension workout, with regards to exercise safety. Critics say that open-chain exercises like leg extensions can damage the knee and that even full-depth squats are safer. Many coaches seem to have gone along with the loudest of voices, avoiding leg extensions. But after examining the research, there are safe ways to carry out the exercises. All you have to do is follow the exact shapes and mix them in terms of how you approach the step.
Performing Leg Extensions Safely
If you have a knee or thigh injury, seek guidance from a physical therapist or strength and conditioning trainer who specializes in weight training rehabilitation. Just don’t be surprised if they tell you to avoid leg extension machines.
Avoid heavy lifting. This is not a machine to try to lift the maximum (1RM), which is the most weight you can lift for just one rep – the heaviest load you can move. You probably don’t want to use it for low-rep, high-load strength conditioning, either.
Don’t do more than three sets of eight to 12 reps with moderate weights. You don’t need to do any high repetition resistance sets on leg extension machines.
Mix up your quadriceps exercises. Make sure you also do squats to lower your body condition, along with leg extension machines.