How To Do The Leg Extension Exercise

Leg Extension

The leg extension exercise is essential when trying to build muscle in your quads. When it comes to burning calories and building muscle, no day is as important as leg day.

This means blasting your quads, hamstrings and gluteus will not only help tighten and tone your lower body but will help burn calories at the same time. Beyond the standard squats, leg presses, deadlifts, and leg presses, what kind of leg exercises should you be doing? 

One you need to add to your leg day lineup is the leg extension. 

What is the Leg Extension?

A leg extension can be done multiple ways. One way is using a leg extension machine, where a cable is attached to a stack of weights and you adjust a pin to control how much weight is lifted. 

Another option is commonly found in home gyms, where the leg extension is connected to your bench and you are able to add weight plates to it. Both leg extension methods target the same area of the body, although the cable leg extension machine will likely allow you to lift more weight (at least the machine is able to hold more weight). 

The lift itself focuses on the quadriceps of your leg. Most of the major lifts you do will hit a variety of muscle groups in the lower body.

For example, depending on how you squat, you’ll touch your hamstrings, quads, glutes, and possibly even your calves. 

Leg extensions are good as it specifically hits your quads. It focuses the entire weight of the lift directly on your quads, which means you don’t have as much assistance with the lift from surrounding muscles. 

When at the gym you’ll find the leg extension machine next to the leg curl machine. Both machines will have you sitting down at a slight angle.

However, with the leg curl machine you’ll start with your legs extended out and a pad placed directly above your knee and right behind your ankle. You’ll then pull your legs back toward your hamstrings (essentially “curling” the weight in to your body). 

With the leg extension you begin with your leg in about a 90-degree angle with a pad right in front of your ankles. With this you’ll bring your legs up so its flush with your quads (Harard Medical, 2019). 

Why You Need To Add The Leg Extension

Why You Need To Add The Leg Extension

There are two reasons why you need to focus on leg extensions during your leg day. 

  • It is the only major lift where you’ll focus specifically on the quads. All other lifts will spread the weight your using to other areas of your lower body. 
  • By strengthening your quads, you’ll improve the rest of your lower body. So, by boosting the amount of weight you can lift with the leg extension you’ll improve the amount of weight you can lift with your squats and deadlifts. 

Even if you’re not focusing on boosting the amount you squat, by focusing specifically on your quads you’ll improve definition and form.

Plus, when you think about it you probably don’t have too many leg exercises to perform. While you might have a half-dozen different bicep exercises, which in comparison is a very small muscle group, the lower body and specifically the quads don’t have many targeted lifts. 

That is exactly why you owe it to yourself to add in the leg extension to your leg day routine. 

Strengthens Your Quadriceps

It’s important to look a bit deeper at the quadriceps so you know exactly what area of the leg muscles your targeting. It should also help you with adding additional secondary leg lifts to your leg day routine as well. 

Your quads are located on the front portion of your legs, running between your knees and your hips. The reverse of the quads includes the hamstrings and the gluteus.

As you may have guessed already, the quads are made up of four muscles (although there is technically a fifth muscle). 

The four muscles include:

  1. Vastus Medialis (inner portion of the thigh)
  2. Rectus Femoris (located around the middle of the thigh, is the only one of the three muscles that does not connect with the femor)
  3. Vastus Intermedius (positioned between the vastus lateralis and vastus medialis)
  4. Vastus Lateralis (portion of the quad that is on the outside of your thigh. 

You can also classify these muscles as “heads.” When you look at your bicep, it is made up of two heads. There is the longer head and the fat head next to it. The same is true with the quads, although it is a bit more difficult to see where the individual heads begin and end. 

As much of human anatomy references the original Greek and Latin words, it’s helpful to know that “medial” means inner, so whenever you see that word used when referencing a muscle group, you know it’s on the part facing the inner portion of the body. Likewise, lateral means it faces the outside of the body.

In fact, most of the muscle is covered up by the Vastus Lateralis and Vastus Intermedius.

As mentioned earlier there is a “fifth” muscle that is part of your quads. This is a skeletal muscle that is under the four main quad muscles. 

This is called the Articularis Genus muscle. It runs from the thigh and stops right above the knee. It helps strengthen and stabilize your leg during a full leg extension, so this is actually one of the main muscles you’ll be strengthening during a leg extension. 

You will be hitting all four of the main quad muscles as well as the fifth skeletal muscle. However, the majority of the lifting is done by the central two quad muscles. Your inner thigh will not be hit as much with this lift, and the far exterior of your legs will not receive as much of the tension from the lift either (University of California at San Diego, 2018). 

If you’re curious as to what lifts you can perform that will specifically hit the inner portion of the muscles and the outer portion of the quads, you will want to perform a side lunge squat.

With this you’ll hold either a single dumbbell at your chest or two dumbbells at your sides. You’ll then lunge out directly to your side (while keeping your torso straight, without twisting). This offers a great stretch and will hit both the outer thigh and the inner thigh). 

Beyond that lift you should also take advantage of the adduction and the abduction leg machines.

When using these machines, you’ll sit down and put the pads on the inside or outside of your knees depending on if you’re doing the adduction or abduction. When doing the adduction, you’ll have the pads on the inside on your knees and bring your legs together (push inward). With the abduction leg machine, you’ll have the pads on the outside of your legs and press outward.

These exercises are good for targeting the inner and outer thigh. 

Setting Up Your Leg Extension Machine

It is of critical importance for you to set up the leg extension machine properly. It takes a few minor adjustments.

By making sure everything is configured properly, you’ll avoid injury while making sure you get the most out of the leg extension machine. Unlike other machines at the gym this will have a handful of adjustment levels and pins you’ll need to use. 

First, adjust the back of the leg extension machine. You’ll want to adjust the back so your knee is just over where the seat ends. You don’t want ample space between where the chair ends and where your knee is. Leaving too much room will place unnecessary strain on your knee. 

Now, you’ll want to adjust the leg pad placement. This is the pad that will go in front of your lower legs. You will ideally want it to be positioned above your foot at around the ankle. 

When you lift your legs up and your leg straightens, the pad will push slightly lower to your foot, so it’s important for you to begin at around ankle level. This way, when you lift your legs up, the pad finishes at around the top of your foot.

You don’t want the pad too high up on your legs, otherwise it places more strain on your ankle instead of using your quad muscles. 

You’ll want to begin at a 90-degree angle with your hamstrings and quads. However, you can bring your legs inward further if you want to increase the stretch placed on your quads. Don’t bring your legs too far under your seat though. The initial placement is the most impactful on your knees. If you have sore knees it’s best to go with the 90-degree lifting angle. If you don’t, you can bring the leg placement in slightly, but for the most part shoot for that 90-degree angle. 

Now that you have everything set up you’ll be ready to begin your leg extension. 

Performing the Leg Extension

First, sit on the leg extension machine with your legs under the pad (feet pointed forward) and the hands holding the side bars. This will be your starting position.

You will need to adjust the pad so that it falls on top of your lower leg (just above your feet). Also, make sure that your legs form a 90-degree angle between the lower and upper leg.

If the angle is less than 90-degrees then that means the knee is over the toes which in turn creates undue stress at the knee joint. If the machine is designed that way, either look for another machine or just make sure that when you start executing the exercise you stop going down once you hit the 90-degree angle.

It’s best to perform one leg extension lift without any weight to make sure all the level adjustments feel good. You want to make sure the pads are tight against your legs. This will ensure you’re secure and there won’t be any slipping during the lift. 

Adjust the weight accordingly and lift your legs up. You’ll want to lift your legs up until your quads and lower legs are straight. Exhale as you do this. Make sure that the rest of your body remains stationary on the seat. Pause for a second on the contracted position.

You don’t need to worry about your knees locking in this position. Slowly lower the weight back to the original position as you inhale, ensuring that you do not go past the 90-degree angle limit.

Make sure you don’t just let your legs drop down. Not only with the weight slam down, but you will be missing an opportunity to work your hamstrings. When you slowly lower the weight down, your hamstring muscles will be in play. If you’re going to do the lift you might as well get the absolute most out of it. 

Sets And Reps For Leg Extension

As is the case with the most other lifts, the number of reps you’ll perform in a single set will vary, depending on the kind of results you’re interested in.

 If you’re looking to bulk up and increase size, shoot for an amount of weight you can lift between eight and 12 reps. If you want to maintain muscle mass while toning the muscles, shoot for about 15 reps. 

In terms of sets you should perform between three and four sets. You should also place this lift toward the end of your leg day routine. Always perform the major, multiple muscle group lifts first. So, on leg day you’ll want to begin with squats and deadlifts. You should also perform your leg press lift before the leg extension as well. 

Once you’re done performing your multiple muscle group lifts you can now move to the leg extension. You should also follow it up with the leg curl machine, followed by the abduction and adduction leg machine. 

Leg Extension


When you get down to it, leg day is the most important day of the workout week. With the sheer size of your leg muscles it doesn’t take much to fully blast your lower body.

This helps burn through more calories while giving you toned, powerful legs. While you should already be doing deadlifts and squats, leg extensions help target specific muscle groups in your quads.

Whether you decide to use the classic exercise machine or opt for a manual free weight method, if you’re not performing a leg extension lift you need to add it to your leg day routine right away. 

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Terry Asher

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After changing his best friend’s life by helping him lose over 70lbs, dropping him down to an amazing 7% body fat, Terry was inspired to be a full-time internet trainer knowing he could do the same for many more. In 2010, Terry published his own diet and fitness e-book that can be purchased on this website. Let Terry help you change your body for the better!
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