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Exercise library · Quads

Leg extension

Knee extension for the quads on a machine.

How to do it

1 of 3

Knees at the machine's pivot

  1. Starting position

    Sit with your back against the pad, knees at the machine's pivot, pad above your ankles and hands on the handles.

  2. The movement

    Straighten your knees until your legs are nearly straight, then lower the pad with control.

Most common mistake

Don't swing the pad up, raise and lower it with control while keeping your hips on the seat.

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Muscle group
Quads
Equipment
Machine
Where
Gym
Logged as
Weight × reps

Muscles worked

The leg extension isolates your quads, the four muscles at the front of the thigh that straighten the knee. Your hips stay still, so no other large muscles need to help. One of the four, the rectus femoris, crosses both the hip and the knee and is stretched further when the backrest is reclined. Try a few settings if the machine allows it.

Common mistakes

  • Only doing the top half. With too much weight, many people only move the last few centimetres. Pick a weight you can move all the way, from knees well bent to nearly straight legs.
  • Letting your stronger leg take over. Both legs share the pad, so a stronger leg can hide a weaker one. Train one leg at a time now and then and compare the two sides.
  • Carrying on when your knee hurts. The leg extension should feel heavy and burn in your thighs, not hurt in your knee. If it hurts, stop the exercise and have it looked at by a doctor or physiotherapist.

Variations and alternatives

  • The single leg extension is the same exercise one leg at a time and shows whether both sides are equally strong.
  • The leg press trains your quads together with your glutes and works as a main lift if you only have time for one machine.
  • The Spanish squat gives your quads plenty of work with just a resistance band, so it works at home.
  • The sissy squat loads your quads with bodyweight alone and is the hardest option here.

Sets and reps

The leg extension suits slightly higher reps. Two to four sets of 10 to 15 reps is a good starting point, and 15 to 20 works as long as you stay in control the whole way. Very heavy, low-rep sets rarely add anything in an isolation exercise. Put leg extensions after your heavier leg work, such as squats or the leg press, when your quads are already warm. Go close to failure on the last sets, but stop once you start to swing. The guide to sets and reps explains how to choose a range.

The weight stack often goes up in fairly big jumps. So add reps first, and raise the weight once you reach the top of the range on every set. If the machine has a small add-on weight, use it for smaller steps. That is what progressive overload looks like on a machine.

Also called

  • bensträck

Swap for

Taken, or missing the equipment? The same movement with something else.

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