Often a subject of discussion if you should completely avoid it or if it makes a fundamental exercise to bulk up on your quads, the Leg Extension exercise does have its purpose. This classic torque-relying leg workout remains to be an essential part of a bodybuilder’s routine as its main goal is to isolate your quads exclusively.

While there are many excellent alternatives like weighted squats and lunges, the Leg Extension is an old-school favorite that we still see to have a steady following. Although it is more favored for aesthetic purposes and muscle definition rather than performance training, a well-rounded set of quads make a fantastic physique.

Before you slide on a Leg Extension Machine and start chasing the pump, let’s break down the know-how and the best leg extension tips to make the most out of this Schwarzenegger-approved movement.

This Ultimate Guide Will Cover:

  • How to do a Leg Extension
  • 3 Leg Extension Benefits
  • Common Leg Extension Mistakes to Avoid
  • Leg Extension Muscles Worked
  • Leg Extension vs Leg Press
  • Our Trainer’s Suggested Reps, Sets, and Programs
  • Leg Extension Variations
  • Leg Extension Alternative Exercises
  • Frequently Asked Questions about Leg Extension

How To Do A Leg Extension

What You’ll Need:

  • Leg extension machine – With this machine, you’re set on doing the leg extension without any problem. Just select the appropriate weight to avoid knee injuries.

Alternative Equipment:

  • Chair – A chair plus your body weight is enough to do a variation of the leg extension.
  • Dumbbells – Using dumbbells will make the seated leg extension variation more challenging.
  • Cable MachineAffix an ankle strap to a low pulley and attach it to your ankle.
  • Resistance Bandas an alternative to ankle weights, loop your resistance band at the bottom of a bench or the rear leg of a sturdy chair and attach the band to your ankle.

Step 1: Position yourself on the leg extension machine

Set the weight stack to a moderate load, and sit on the machine with your knees positioned in line with the equipment’s axis of rotation. Put your hands on the handlebars.

Step 2: Arrange your sitting posture

You should sit tall with a neutral neck and head position, and your chin should be tucked throughout the motion. Keep your back against the pad of the machine, tighten your core, and pull your glutes towards your seat.

Step 3: Go to the starting position

Put your lower leg nearly touching the padded bar as it should rest just above your ankle. Position your knees to point forward and your ankles in line with your knees. Pull your toes slightly to your knees. This will be your starting position.

Step 4: Start the upward movement

Initiate the upward motion by squeezing your quads and straightening your legs.

Step 5: Lift your legs

Raise your legs until your knees are straight without locking them.

Step 6: Squeeze and return

Once you reach the top of the movement, squeeze your quadriceps for a few seconds, then slowly go back to the starting position. Remember to bend your knees until your ankles are underneath, and the weights should not come into contact with the weighted sack during the downward movement. Be sure to adjust your seat correctly and sit in an optimal position.

3 Leg Extension Benefits

1. Perfect for Beginners

Free weights can be intimidating, especially if you are a beginner at resistance training. With leg extensions, getting the proper form, movement, and posture becomes easier since you have an exclusive machine to perform the workout with. This machine is an excellent start for all gym rookies!

2. Isolates the Quads

The leg extension is an open-chain kinetic exercise that is perfect for working your quads. Open-chain workouts like this are effective for isolating specific muscles, which in this instance is your quads. Isolating your quads is crucial if you want to see more definition in your upper leg muscles or if you want to avoid a hamstring injury. 

3. Enhances Muscle Mass

Doing leg extensions will help you increase the size and strength of your quad muscles. Building the size of your quads is perfect if your current training program emphasizes your hamstrings or glutes as it can balance the muscles in your legs.

Common Leg Extension Mistakes to Avoid

Too much weight 

The leg extension machine is not meant to try for a maximum lift (1RM). Since this exercise relies on the torque used in moving the weight, you don’t need to load the equipment too much to get the benefits. Don’t do low-rep, high-load strength conditioning, or you may be at risk of ligament strain.

Doing high reps 

Performing more reps will not give you more advantage when it comes to leg extensions. Don’t go beyond three sets of eight to twelve reps at moderated load. Focus on the quality and form throughout the movement to make the most out of the lifts.

Fast execution 

You will lose the essence of this workout once you start using momentum to lift the weight. Do it slowly and control it to keep your muscles activated.

Locking the knees 

If you lock your knees, it can strain your knee joint. Make sure to avoid it when you are in full extension and slowly lower and lift the weights as the movement must rely on torque. Do not lock out your knees and focus on the tension. The more your muscles are exposed to tension, the bigger it gets. Keep the knees bent slightly bent at the top of the movement. 

Improper breathing 

While it may not seem much, watching your breathing when performing leg extensions is essential. Ensure that you exhale as you extend your legs and inhale when you lower them down. And always engage your core in the movement.

Leg Extension Muscles Worked

The muscles that you target when executing leg extensions are:

  • Vastus medialis
  • Vastus lateralis
  • Vastus intermedius
  • Rectus femoris

Since the leg extension workout is an isolation exercise, it only targets your quadriceps, which are found on the front of your thigh muscles. This includes the vastus medialis, vastus lateralis, vastus intermedius, and rectus femoris. 

With this workout, the only movement you do is straightening your legs at the knee, so the engagement will not reach your glutes, hips, or hamstrings. The exercise focuses on the muscle development of quads. If your goal is to achieve quads hypertrophy or if you are training purely for bodybuilding, the leg extensions should be integrated into your workout.

Our Trainer’s Suggested Reps, Sets, and Programs:

For Bulkier Quads

Leg extensions will blast your quadriceps muscles in isolation, building their size. However, leg extensions alone are not enough to get the big and bulky quads you’re aiming for. Start with this exercise, then perform moves that mirror the everyday movements of your knees. 

Try this workout plan: twenty reps of leg extensions followed by ten reps of walking lunges on each leg. Perform four sets.

For Strength Training

This quad building isolation exercise can help you rehabilitate your quadriceps muscles when it needs strengthening. Set a moderate load and perform three sets of eight to twelve repetitions. However, make sure that you don’t have existing knee issues and don’t use extreme loads.

Leg Extension Variations

You can execute different leg extension variations in a leg extension machine by changing your foot positions. However, if you don’t have a leg extension machine, you can try these “no leg machine variations” to continue building muscle in your quads!

Seated Bodyweight Leg Extensions

In this variation, all you need is a chair, and since you’ll be executing this exercise with your body weight, it’s less strain on your knees. 

Sit on a chair with your back straight and your feet hip-width apart. Extend on the knee until you fully extend your legs, hold it for a couple of seconds, and go back to the starting position. Repeat on the same side and finish one set before swapping.

Standing Leg Extension

Apart from your quads, this variation will also target your core and can help improve your balance and coordination! You’re going to perform it with one leg at a time, extending and holding it to get the full extension. If you want to make it harder, add resistance bands, anchor it behind you, and attach it to an ankle strap. 

Cable Leg Extensions

If you don’t want to use a leg extension machine, then use a cable machine instead! In this variation, you’ll put an ankle strap in a low pulley and attach it to your ankle. Then you’ll stand facing away from the pulley and grab onto the cable machine to perform a standing leg extension.

Kneeling Leg Extension

Another movement that will only require your body weight is the kneeling leg extension (also called natural leg extension). Here you start in a kneeling position with your knees hip-distance apart. Then place your arms reaching out in front of you and begin to lean backward as far as you can. 

Ensure that your engaging your quads, core, and glutes as you perform this variation. Activating these muscle groups will help you maintain your posture and reduce any risk of injury.

Lying Leg Extension

Here, all you’ll need is a resistance band and a bench. Just wrap the resistance band around the bottom of your bench and position one leg pointing up, so it’s at a 90-degree angle with your torso. Bend your lifted leg at the knee, so your lower leg will be parallel to the floor. Hold this position a bit before stretching your legs. Repeat and finish one set before switching.

Leg Extension Alternatives

If you’re worried about knee pain and the risks leg extensions may pose, you can do these Alternative Exercises instead. Don’t let your quads miss out on the burn just because you don’t want to perform leg extensions! 


Lunges is a great alternative since it’s pretty easy and super accessible. If you are a newbie to working out, lunges are the perfect starting point as it’s an excellent single-leg movement. Once you get used to it, you can start doing other variations to target a different muscle group and challenge your body more. Some of the variations include forward lunges, barbell lunges, and reverse lunges.


This exercise is excellent in engaging your joint extensions, at the gym or at home, with low injury risk. Like lunges, step-ups are a single-leg exercise, so they have the same benefits, which is training both sides of the body equally. 

Isometric Leg Tuck

Isometric leg tuck trains your thighs, making it an ideal leg extension alternative. When doing this movement, you don’t need any special machine. You’re all set with just a medicine ball and an exercise mat!

Cyclist Squats

Another leg extension alternative that you should not skip out on is cyclist squats or quad squats. Here, you’ll position your feet close together with your heel raised. Because of this, your hips will move straight down, forcing your quads to work harder. To perform it, you’ll need a weight plate or curb that is at least three inches high.

Bulgarian Split Squats with Dumbbells

This alternative will engage your glutes and hips. It’ll also activate other muscles, including your hamstrings and quads. With the Bulgarian Split Squat with dumbbells, you’ll need a dumbbell and a bench. Make sure that the bench you’ll be using is knee-height or slightly lower. 

Since this exercise will require good balance, try it without a dumbbell first if you’re just new to it. Once you get used to the movement, that’s the only time you can train with dumbbells.

Leg Press

If you have a Leg Press Machine in your gym, then you can do Leg Presses as an alternative to leg extensions. Because of the equipment, this exercise becomes safer and more accessible for beginners compared to other workouts that use free weights. Similar to leg extensions, using dedicated equipment for the movement will help you perform it in proper form.

The leg extension is an isolation exercise that you need to engage your different vastus muscles. However, that’s not enough to build up solid and bulky quads, so you should include various compound exercises in your training program as well! The more muscles you target in your upper and lower legs, the better your lower body will look.

Frequently Asked Questions

The leg extension isolates the action of the knee extension, which engages all parts of your quadriceps muscles. If you want to focus on building your quads, then this exercise will help you get to where you want to be. However, leg extensions alone cannot improve the overall strength of your legs, so you also need to do variations and alternatives to target other muscle groups.

Studies show that leg extension can give you superior muscle growth in the rectus femoris compared to squats. However, Squats produce more significant results when it comes to the largest of the four quad muscles. In the end, you’ll need to incorporate both exercises in your training program to shape your quads perfectly!

Is the leg extension safe?

While leg extension is an excellent exercise for improving your quads, there are drawbacks that you need to be aware of. Since this movement applies constant tension in your anterior cruciate ligament (ACL), you should not do it when you have any ligament injuries. 

Also, if you’re not careful when performing this exercise, you may increase the risk of lateral patellar deviation. It means your knee caps can slide left to right unnaturally.

Are leg curls and extension good?

Both the leg curls and leg extension are good for you if performed incorrect form. If the leg extensions target the muscles in front of your legs (quads), the leg curls engage the muscles in the back of your legs (hamstrings). Leg extension will help you enhance your squats, while leg curl will train you for deadlifts.

If you’re creating your own leg program, you should do leg extension before proceeding with other exercises since it’s the only workout that fatigues only your quads. In a routine of three to four quad exercises, put leg extensions at the top of your list, followed by squats and leg presses.

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