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Leg Extension Benefits: Build Your Quad Muscles

The leg extension is an excellent exercise for strength training, specifically targeting the quadriceps. Incorporating this exercise into your lower body routine can effectively enhance muscle definition in your legs. While compound exercises engage multiple leg muscles, leg extensions provide significant isolated volume to the quads, resulting in optimal leg development.

Why do you need to train your quads? From a functional standpoint, you need your quads to move about. Your quads work to move your lower and upper leg at your knee and hip joints, respectively. 

Stronger quads also mean better athletic performance and fewer injuries. This study shows that weak quads could increase your risk of knee osteoarthritis (1). Your quads play an important role in all your leg movements, so you must keep them strong and flexible. Leg extensions should be integrated into every leg workout you do!

Seated Leg Extension - Top Range of Motion

What Are Leg Extensions?

The leg extension exercise is done on a leg extension machine, sitting on a pad or bench to raise a padded bar using your quads. They fall under open-chain kinetic exercise as your legs aren’t stationary when doing them, so the chain of movement is open. Experts and athletes agree that it offers a full range of motion for massive muscle gains and has a low impact on your joints. 

The leg extension is an isolation exercise that targets your quadriceps femoris. This group of muscles comprises the vastus lateralis, vastus intermedius, vastus medialis, and rectus femoris. Your quads are the largest muscles in your body, and you need them to walk, squat and maintain a good posture.

What Is a Leg Extensions Machine?

The leg extension machine is a lever machine designed to isolate your quads by doing a knee extension with weights. This weight training equipment typically has a padded bench where you can sit to extend your legs against resistance using padded rollers. When performing leg extensions on this machine, you lift the weight with your leg by extending your knees, then lower the weight back down to the starting position in a controlled manner (2)

The seated leg extension machine suits all fitness levels, whether beginner, intermediate, or advanced. Most leg extension machines are divided into plate-loaded or selectorized machines, depending on the type of load that they use. The plate-loaded leg extension machine is often less costly since it doesn’t come with its own weights.

Many home gym owners use the plate-loaded leg extension machine because of costs. They can often use the plates they already have at home. However, selectorized leg extension machines have the advantage of built-in weight and provide uniform resistance while being convenient and faster to switch weights on.

Another thing to also consider when getting a leg extension machine is machine style. You can use the traditional leg extension or an iso lateral leg extension with superior stretch adjustments. A combo leg curl machine is combined with leg extension and leg curl machines. 

Plate Loaded Leg Extension Machine


The Benefits of Leg Extensions

If your main cardio is walking or running, this mainly targets your hamstrings. You need a routine that builds your quads. This will help you add more to balance your overall leg strength. 

Leg extensions might not be functional movements, but they train a muscle important for daily functionality. Because of your quads, you can only walk, run, or stand upright properly. That’s a few of the main benefits of leg extensions, and below are some other useful benefits.

1. Strengthens Quadriceps 

Leg extensions target your quadriceps muscles, the largest muscles on the front of the thigh. It does this by performing a knee extension, and research shows that knee extensions effectively increase leg strength (3). Strong quads are vital to your athleticism and power output in activities that require leg power.

2. Enhances Knee Stability 

The biomechanics of leg extensions uses a torque force that causes you to push through your quads to straighten your knee. As a result, your patella and quadricep knee attachment ligaments strengthen both. Regularly performing leg extensions reinforces this biomechanic and helps to reduce your risk of injuries by improving your knee stability. Put simply: leg extensions are a great way to improve knee stability

3. Improves Athletic Performance 

You use your leg power in running, cycling, and even football. Strengthening your quads and thighs will improve athletic performance during those activities. Your quads help your overall stability and balance, so those metrics also improve from doing leg extensions. Strong quads will improve your lifts and give you better performance in the gym. Your quads affect your lower leg movements and upper leg movements significantly. These come into play during squats, deadlifts, and other lower body strengthening exercises.

4. Convenient and Easy to Perform 

The leg extension exercise is a great exercise because it's easy to perform. You can do leg extensions with as little equipment as a bench or chair and some resistance bands. You can also find a variety of leg extension machines in basically every commercial gym. This is a beginner friendly exercise that's easy to do with proper form and it has a low risk of injury. 

How to Properly Perform Leg Extensions

To get the most out of your leg extensions, doing them in perfect form is important. This is also the only way to ensure they engage the right muscles. Here is a step-by-step guide on how to do leg extensions the right way.


  1. First, choose a weight that will give you moderate loads for about 10 reps.

  2. Sit on the leg extension chair and adjust it so the pad is at the top of your lower legs around your ankles. 

  3. Put your hands on the machine's hand bars and brace your core. This is your starting position. 

  4. Lift the weight till your legs are almost straight, ensure your back remains on the backrest, and your knees don’t lock.

  5. Lower the weight back to the starting position to complete the rep.

Leg Extension Mistakes to Avoid

Common mistakes to avoid for a safe and effective workout include:

  1. Lifting too heavy can put a strain on your knee joint and give you injuries. Start with a light to moderate weight and work up from there.

  2. Keep your back on the backrest and avoid arching or slouching, which could lead to back pain.

  3. Going too fast will take the target away from your muscles because you'll use momentum. 

  4. Locking your knees at the point of full extension could lead to knee pain. Keep a slight bend in your knees while fully contracting your quads.

  5. Let the rotation axis of your knees be in sync with that of the machine to avoid over-expression of your knees. This means your knees shouldn’t be too far in front of or behind the machine’s axis. 

Leg Extension Tips for Beginners

Leg extensions are beginner-friendly. Remember that starting slow and using less weight is important if you’re new to the lift. Control the movement, and don’t kick the weight up. Slowly extend your knees until your thighs are parallel to the floor, pause, then slowly bring the weight back down to the starting position. It’ll also benefit beginners to do reps in the eight to 10 rep range to ensure the weight isn’t too heavy but still enough to spur muscle growth.

To improve their ability on leg extensions, beginners can also strengthen their leg muscles with other equipment. Using dumbbells or kettlebells to perform squats will carry over to the leg extension. 

It’s important to take time to rest long enough between sets so that your muscles can be recovered for each set. Beginners should rest for about two minutes before moving on to their next set. This is an important key to muscle growth. 

Seated Leg Extension Machine with Weight Stack

Integrating Leg Extensions Into Your Workout Routine

Leg extensions are most effective when you use them as an accessory exercise. This means performing them as a finisher to heavier compound exercises. For example, start your workouts with squats or leg presses, then finish them with leg extensions. If you're an expert, four or five sets of eight to twelve reps will help you strengthen and grow your quads. As a beginner, two sets may be sufficient for your training. 

This is one of those leg exercises that can provide you with a really good burnout. Try doing leg extensions with drop sets or high rep sets. You can even superset them with leg curls, a lower body staple. 

They can also be a great warm up for your legs. Try doing some high rep, lighter weight sets before you start your workout on your next leg day.

Leg Extension Precautions and Potential Downsides

Leg extensions are simple and work for athletes at all levels. If done incorrectly, leg extensions could lead to strains and pain. Using a load that is too heavy or locking out your knees at the top position could cause knee injuries.

People with a history or potential for knee injuries might be better off trying other routines. The biomechanics of leg extensions will place a significant amount of stress on your knees. Generally, open-chain kinetic exercises are not ideal for those with knee problems.

However, if you don’t have any knee injuries, try the leg extension with light weight and see how that feels before adding additional weight. 

Leg Extension Benefits Conclusion

Leg extensions are a key isolation exercise to build your quads and lower body strength. Strong leg muscles are important for daily movements and activities, such as standing and walking. The strength of your quads also affects your athletic performance and helps with running and jumping ability. 

The leg extension machine is a safe and easy way to add leg extensions to your routine. It could either be weight loaded or selectorized. Leg extension machines are also ideal for beginners looking to strengthen their lower body muscles. 

Since the biomechanics of leg extensions includes doing a knee extension, it’s not advised for people with knee problems. Doing this exercise with less weight or improper form could also lead to knee problems. So check this guide for more information on how to do leg extensions properly to avoid injuries. 

Considering this, there's no better way to target and strengthen your quadriceps. If you're reading this, it's high time you added leg extensions to your workout routine and witnessed the incredible benefits firsthand.

Have you given this exercise a shot yet? We'd love to hear from you! Share your insights on how it went and tips for performing the routine effectively. And remember to be a great friend and pass this exercise to anyone who could use it!


  1. Segal, N. A., Glass, N. A., Torner, J., Yang, M., Felson, D. T., Sharma, L., Nevitt, M., & Lewis, C. E. (2010). Quadriceps weakness predicts risk for knee joint space narrowing in women in the MOST cohort. Osteoarthritis and cartilage, 18(6), 769–775. 

  2. Kanada, Y., Sakurai, H., Sugiura, Y., Arai, T., Koyama, S., & Tanabe, S. (2019). Evaluation of the relationship between joint torque and angular velocity using a modified leg extension machine. Fujita medical journal, 5(4), 85–91. 

  3. Vincent, K. R., Vasilopoulos, T., Montero, C., & Vincent, H. K. (2019). Eccentric and Concentric Resistance Exercise Comparison for Knee Osteoarthritis. Medicine and science in sports and exercise, 51(10), 1977–1986. 

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