Leg Extension
Straightening your knees on a machine: the only exercise that fully isolates your quads.
Also known as: quad extension, leg extension machine
- Level
- Beginner
- Equipment
- Leg Extension
- Type
- Isolation
Muscles worked
How to do it
- Adjust the backrest so your knee lines up with the machine's pivot.
- Set the pad just above your ankles.
- Straighten your legs until your knees are almost locked and squeeze your quads.
- Lower slowly to about 90 degrees.
Form cues
- Hold the handles so your hips stay down.
- Pause for a second at the top.
- Lower slowly without banging the stack.
Common mistakes
- Knee out of line with the pivot: the joint suffers. Adjust the backrest.
- Kicking the weight up: control the lift.
- Lifting your hips off the seat: reduce the weight.
Sets and reps
3 sets of 10-15 reps with 60-90 seconds of rest, at the end of a leg session.
Variations
Same movement, different equipment. Pick based on what you have and what you want from the leg extension.
Single-leg extension
One leg at a time to fix imbalances.
How to do it
- Sit on a leg extension machine and place one foot under the pad.
- Rest the other foot on the floor or let it hang.
- Extend the working leg until it is nearly straight.
- Squeeze the quadriceps at the top.
- Lower the leg back down under control.
- Complete reps on one side, then switch.
- Primary
- Quads
Banded terminal knee extension
Straightening your knee against a band: common in rehab.
How to do it
- Anchor a loop band to a sturdy upright at knee height.
- Step into the loop so the band sits behind one knee.
- Step back so the band pulls the knee into a slight bend.
- Extend the knee fully against the band, contracting the quad.
- Return slowly. Complete reps per side, then switch.
- Primary
- Quads
Reverse Nordic curl
Kneeling, you lean back: deep quad stretch with no machine.
How to do it
- Kneel on a pad with your feet flat and torso upright.
- Keep your hips extended and core braced.
- Slowly lean your torso backward while keeping your body in a straight line.
- Lower as far as you can control with your quadriceps.
- Pull yourself back up to the starting position.
- Primary
- Quads
- Secondary
- Hip Flexors, Abs
FAQ
Is the leg extension bad for your knees?
Not with sensible weight and a well-adjusted machine. It's even used in rehab.
Does it build leg size?
Yes, especially the rectus femoris, which squats work less.
Toes in or out?
It changes very little. Keep them straight and focus on full range.
What muscles do the leg extension work?
They mainly work the quads.
Add the leg extension to your next workout
Log your sets and weights, and see how each muscle progresses in the app.
