Machine · Legs and glutes
Leg extension machine
The leg extension is the seated machine where you straighten your knees to work your quadriceps. Great to feel the front of your thighs working without worrying about balance. Useful for beginners and also to finish a hard leg workout.
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The essentials
- Line your knees up with the pivot.
- Straighten your legs, pause, then lower slowly.
Muscles worked
- Primary
- Quadriceps
Setup
- Adjust the backrest so your knees line up with the machine’s pivot point.
- Set the pad so it rests just above your ankles, not on your feet and not too high on your shins.
- Sit with your hips all the way back and your lower back against the pad.
- Pick a weight on the stack that lets you control both the lift and the lowering.
- Hold the handles or the sides of the seat to keep your body stable.
How to do it
- Sit up straight with your back against the pad and feet about hip-width apart.
- Start with your knees bent around 90 degrees or a bit more, weight resting in the start position.
- Exhale as you tighten your quads and extend your legs in about 2 seconds, without swinging.
- Lift until your knees are almost straight, stop for a brief moment at the top while keeping tension.
- Inhale as you lower the weight slowly in 2 to 3 seconds, back to the starting position under control.
- Repeat with a smooth motion, keeping your lower back on the pad and not letting the stack slam down.
Common mistakes
Kicking the weight up with momentum
Instead : Slow down the lift, take about 2 seconds to straighten your legs, and add a short pause at the top. Drop the weight if you need a big swing to get it moving.
Letting the stack drop at the bottom
Instead : Stay in control on the way down, aim for 2 to 3 seconds. If the plates crash together at the end, lower the weight and focus on resisting the pull down.
Seat too far from or too close to the pivot
Instead : Reset the seat so your knees line up with the machine’s pivot point. Adjust until the movement feels natural without weird pulling on your knees.
Hips lifting or arching the lower back
Instead : Keep your hips back in the seat and your lower back on the pad. Grip the handles firmly and choose a weight that doesn’t pull you off the bench.
Coach tips
- Start light to feel your quadriceps working without any knee discomfort, then build up slowly.
- Breathe out as you extend your legs and in as you lower them to keep a steady rhythm.
- You can slow the lowering phase to about 3 seconds to better control the weight and feel your quads more.
- The weight stack makes drop sets easy: when you’re near failure, pull the pin to lower the weight and go again right away to extend the set.
Variations
- Leg extension with a 1–2 second pause at the top to increase time under tension for the quadriceps.
- Single-leg extension to address side-to-side imbalances and improve control.
- Partial reps at the end of a set in the top third of the movement to further fatigue the quadriceps.
Sets and reps
This machine is often used for 3 to 4 sets of 10 to 15 reps, usually toward the end of a leg workout. It’s also common to see longer sets with successive weight drops using the stack.
Exercises on this machine
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Common questions
Where should I feel the leg extension?
You should mainly feel the front of your thighs, the quadriceps. If you feel sharp knee pain or anything unusual, stop the exercise and talk to a professional.
Should I fully lock out my knees at the top?
You can go close to full extension, but avoid snapping or jamming the joint. Keep a small bit of tension, like you’re stopping the knee from locking all the way out.
How do I pick the right weight on leg extensions?
Choose a weight you can lift and lower under control, without swinging and without pain. You should be able to keep the same tempo across all the reps in your set.
Is single-leg extension better than both legs?
It’s just different. With both legs you can usually go a bit heavier and move a bit faster. With one leg at a time, you work on imbalances and stability, often with a slightly lighter load.