How To Do the Perfect Leg Extension

Build muscle and get stronger legs using the leg extension machine in the gym

What is a leg extension?

You’ve probably seen the leg extension machine in the gym (even if you haven’t been on it). It’s a weights machine that you sit in, with a padded roller above your knees and another on top of your ankles. You flex at the knees to straighten your legs, which focuses all the work on your quadriceps muscles.

But you might be wondering how to do leg extensions properly, what muscles leg extensions are good for, and even if leg extensions are better than squats or lunges.

Commonly Asked Questions On Leg Extensions

What are leg extensions good for?

Leg extensions exercises fall into the same category as leg exercises that you’d do on lower body day like lunges and Bulgarian split squats, but leg extensions are considered an isolation movement because they only move one joint (the knees).

What muscles do leg extensions work?

The way the leg extension machine is designed holds your upper body and thighs still, so you can only move your lower legs. This is a great way to isolate your quads to strengthen the front of the thighs without involving any other leg muscles.

Leg extensions work all four heads of your quadriceps muscles, and allow you to maintain tension on the muscles during the concentric contraction, the squeeze at the top, and the eccentric phase.

Is leg extension better than squats?

Leg extensions are neither better nor worse than squats and lunges – they’re different. Leg extension machines are usually pin-loaded, which means the weight is controlled by a stack right next to you. Should leg extensions be heavy? No, you won’t be able to lift as much weight using a leg extension machine as you can doing squats, and keeping the movement lighter is good for your knees.

Leg extension machines hold your body in place, and pin your upper legs to the padded seat. You will usually have handles to hold, too, which prevents you swinging your body. This all means the leg extension movement is small and controlled (unlike a barbell squat or dumbbell lunge). And you’ll need to keep the weight light on a leg extension machine, which is safe for your knees.

Will leg extensions make your legs bigger? Yes, especially if you combine them with other exercises like squats, lunges, step ups, and leg press. Leg extensions are a great way to build lower body strength because they isolate growth in the quads.

What are the benefits of leg extensions

Leg extensions isolate your quads

The leg extension machine supports your back like a chair, and holds your upper leg and knee in place. This means you will isolate all the work in one or both quads so you can build strength and size.

You can do dropsets on the leg extension

Dropsets are a great way to add volume to your workout, and the leg extension machine makes it super easy to drop the weight through a triple dropset until you’re working to failure.

Leg extensions are a great finisher for leg day

Because leg extensions isolate the quads with a relatively light weight, they are a brilliant finisher exercise for lower body day workouts, and a good option for a lighter leg workout if you want to go running.

Leg extensions give you a good muscle pump

Getting a good pump isn’t everything, but it sure is rewarding! You will be able to see and feel the pump happening as you sit on the leg extension working your quads.

Leg extensions are safe for your knees

Leg extension exercises can a smarter choice than bigger compound movements like squats and lunges, because the movement is more controlled.

Are leg extensions OK for knees?

It might seem as though doing leg extensions could be bad for your knees, but the opposite it true for most people. In fact, leg extensions are such a safe exercise that they are often advised as rehab work after knee or quad muscle injuries.

Leg extension machines hold your body in place, and pin your upper legs to the padded seat. You will usually have handles to grip on to, too, which helps prevent you from swinging your body. This all means the leg extension movement is small and controlled (unlike a barbell squat or dumbbell lunge). And you’ll need to keep the weight light on a leg extension machine, which is safe for your knees.

When to avoid doing leg extensions

Whilst we think leg extensions are a safe, effective exercise, they aren’t always the best choice for your leg day programming. Here are the key reasons to steer clear of the leg extension machine.

You’re short on time

If you don’t have much time for a leg workout, stick to the big compound exercises with free weights (like barbell or dumbbell squats, lunges, or the leg press).

You feel any knee pain

It goes without saying that you shouldn’t jump on the leg extension machine if your knees are hurting.

You’ve already done a high volume leg workout

Leg extensions are best for light, reppy work to pump the quads, so if you’ve already achieved that in your workout there’s no need to do more.

How to do a leg extension properly

It’s important that you know how to do safe leg extensions. Take some time to set the machine up. The back of your knee should be at the front of the seat (adjust the back pad to move you forward or backwards). The rollers should be on top of your leg just above the knee, and on top of your ankle. Do some very light reps to check these positions.

Once you start working out on the leg extension, use the handles to keep your body driving back and down into the seat. Lock your knees at the top of the movement, but don’t swing your legs up and down. Control the entire rep from start to finish.

Leg extension variations

Dropsets

Do 10-12 reps at a high weight, then quickly drop the weight to around 60% and do 10-12, then drop again to a very light weight and rep out until failure.

21s

Choose one weight and do 7 reps in the top half of your range, 7 reps in the bottom half, then 7 full reps.

Slow eccentric

Fast up, pause at the top, and lower down for a count of 4. This one will get real spicy, real quick! How long should you hold the leg extension at the top of the rep? Count 1-2 seconds before starting that controlled lower down.

Find a gym near you with great leg day equipment including a leg extension machine. Hussle gives you access to a huge network of gyms, pools, spas and health and fitness apps, all accessible through a single pass. Sign up here.