Leg Extension: how to do it right
In short: The leg extension isolates the quadriceps by loading it the most in the shortened position, with the knee straight.
How to do it, step by step
- 1Wedge your back in well, the axis of your knee aligned with the machine's rotation axis.
- 2Position the pad on the lower shin, above the ankles.
- 3Straighten your legs by pushing forward, with no jerking.
- 4Lock out at the top, knees straight, and squeeze the quadriceps hard for 1 second.
- 5Control the return slowly without letting the weight drop back on its own.
The mistake to avoid
Don't snap your knees straight, control the movement.
Other common mistakes
- Not fully straightening your legs makes you miss the most useful zone, go for full extension and lock out.
- Swinging and using momentum takes the load off the quad, slow down and control each phase.
- Loading too heavy blocks the final extension, lighten up to lock out firmly at the top.
- Letting the return drop on its own ruins the eccentric, actively slow the descent.
Muscles worked
- Main:
- Quads
The four heads of the quadriceps: vastus medialis (inner), vastus lateralis (outer), vastus intermedius and rectus femoris. They extend the knee. The vastus medialis is recruited mostly at the very end of extension, which makes the final lockout valuable.
What to replace it with
Same muscle, same part of the movement: these exercises do the same job.
Frequently asked questions
How do I do this exercise?
Wedge your back against the backrest, the axis of your knee aligned with the machine's rotation axis, and the pad on the lower shin above the ankles. Straighten your legs with no jerking, lock out at the top and squeeze the quadriceps for 1 second. Then slow the return, do not let the weight drop back on its own.
How far up should I go?
Go for full extension, legs fully straight: it is at the end of the movement that the quadriceps works the hardest, especially the vastus medialis. Do not skim over this zone, that is where all the work is. Hold a contracted pause at the top instead of loading heavy and rushing the end.
I don't feel anything, is that normal?
You should feel the quadriceps burn, especially above the knee on the inner side, the vastus medialis. Lower the weight, go to full extension and squeeze a firm 1 second at the top: you will feel it far better than with sloppy heavy weight.
How fast should I do the movement?
Straighten the legs firmly but under control, squeeze 1 second at the top, then slow the return over 2 to 3 seconds. It is the slowing and the contracted pause that do the work, never momentum.
How do I breathe?
Inhale with your legs bent, exhale as you straighten them and keep the exhale through the second of contraction at the top. Trunk braced and hips flat against the seat so you do not arch.