Exercise library / Legs
Leg extension
Legs · Machine
The leg extension has a bad reputation it does not deserve. The claim that it wrecks knees comes from studies on injured joints with heavy loads at full extension, not from ordinary training with sensible weight.
It does something no multi-joint exercise does: it loads rectus femoris, the part of the quadriceps that crosses the hip, in a position squats and leg presses do not reach.
Sets, reps and RIR
Machines and cables hold the path for you, so you can work closer to failure than with free weights.
RIR means reps in reserve: how many you could still have done when you racked it. RIR 2 is two short of failure.
How to do it
- Set the backrest so your knee lines up with the machine's pivot.
- Put the pad just above the ankle, not up on the shin.
- Hold the handles and press your lower back into the support.
- Extend to almost full lockout, without swinging.
- Squeeze for a moment at the top.
- Lower under control over two to three seconds to the start.
Common mistakes
- Swinging the weight up
- Speed through the last part of extension is the one thing in this exercise that is genuinely hard on the knee. Control it throughout.
- Lifting off the seat
- Pushing the hips up to get the weight moving means it is too heavy.
- Pad too high
- A pad in the middle of the shin rather than at the ankle shortens the lever and makes the weight misleading.
- Half reps
- The last twenty degrees are where the quads work hardest. They are also where most people stop.
How it differs from the neighbouring variants
Squats and leg presses load the quads together with glutes and hamstrings, and that is where strength is built. The leg extension isolates, which makes it the place to train quads hard without spending your back or hips.
The sissy squat does something similar with body weight and stretches rectus femoris further. The hack squat sits closer to a squat but keeps the torso supported and gives the quads more than a free squat does.
What it suits
Leg extensions fit at the end of a leg session, at ten to fifteen reps. They are also a good light warm-up before heavy squats, because they warm the knee without costing anything. If you have known knee pain, start with a short range in the upper half and build from there.
Muscles worked
Primary: Quads.
Estimate your one-rep max
Epley's formula, from a set you have actually done. It is an estimate, and it drifts above eight reps, so keep the input between one and twelve.
Enter a set to see the estimate.
What it is called elsewhere
- Norsk Beinextension
- Svenska Benspark
- Dansk Leg extension
- Deutsch Beinstrecken (Maschine)
- Español Extensión de piernas
- Italiano Leg extension
- Português Cadeira extensora
- Русский Разгибания ног в тренажёре
- Français Leg extension (machine)
Related legs exercises
athlate logs this exercise, keeps the numbers, and tells you what you lifted last time.