Single-Leg Extension: how to do it right
In short: The single-leg leg extension isolates one quadriceps at a time by loading it the most in the shortened position, leg straight.
How to do it, step by step
- 1Brace your back against the backrest, knee axis lined up with the machine's axis of rotation, pad on the lower shin.
- 2Work only one leg: keep the other foot planted and your pelvis flat, without lifting it.
- 3Extend the knee until the leg is almost straight, then squeeze the quad hard for 1 second at the top.
- 4Control the return over 2 to 3 seconds without dropping the weight, until you feel the stretch.
- 5Stay in a clean range: do not use torso momentum to throw the leg.
The mistake to avoid
Don't swing the leg, extend your knee with control.
Other common mistakes
- Swinging the torso to throw the leg: lock the trunk and let the knee alone work.
- Not going up to lockout: you miss the peak tension, go for full extension and squeeze at the top.
- Letting the weight drop: brake the return for 2 to 3 seconds to keep the tension.
- Letting the knee drift off the machine axis: realign it to avoid pointless shearing.
Muscles worked
- Main:
- Quads
Quadriceps of the working leg: the rectus femoris, vastus lateralis, vastus medialis (the teardrop above the knee) and vastus intermedius. They all handle knee extension. The single-leg mode forces each leg to work alone, which corrects a right/left imbalance and calls on the hip stabilizers a little to hold the pelvis.
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?
Brace your back against the backrest, line your knee axis up with the machine's axis of rotation and put the pad on the lower shin. Work only one leg: keep the other foot planted, your pelvis flat, and extend the knee until the leg is almost straight. Squeeze the quad for 1 second at the top, then control the return.
How high should I go?
The tension is maximal in the shortened position, leg straight, so go for full extension and squeeze at the top: that is where the quad works the hardest. At the bottom, leg bent, it is easy, but still let it come down to keep the range. Go for the full range you can control, without squirming or lifting your pelvis.
I don't feel anything, is that normal?
You should feel the quadriceps, especially at the top with the leg straight. Once you are in the straight position, imagine crushing the pad upward and squeeze the quad like you are trying to make it tremble for 1 second. Go lighter than usual, the value is single-leg contraction quality, not load, and compare your two legs rep by rep.
How fast should I do the movement?
Rise firmly, lock out and squeeze for 1 second at the top, then brake the return over 2 to 3 seconds. It is that hold at the top plus the braking that do the work, not speed. Never let the weight drop.
How should I breathe?
Breathe in at the bottom, breathe out as you rise toward extension and keep your belly braced to stabilize the pelvis. On the 1-second hold at the top, briefly hold the air without forcing, then breathe out fully. Hold the handles so you do not compensate with your upper body.