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Leg Extensions & Curls vs Squats | Which is better?

Every gym-goer knows the rush of a good leg day—the burn that tells you you're getting stronger, the challenge of pushing past your limits, and the satisfaction of walking away knowing your lower body just got a serious upgrade.

Among the arsenal of moves at your disposal, leg extensions and leg curls have become staples, while squats reign supreme as the undisputed king of leg workouts. But how do these exercises stack up against each other?

Diving into the world of leg extensions, leg curls, and squats is like unlocking the secret recipe for lower-body prowess. Each exercise brings something unique to the table, targeting different muscles and testing your strength in varied ways.

Stick around as we break down the nitty-gritty of these three leg day champions. Whether you're just starting to dip your toes into the fitness world or you're the one turning heads with your squat PR, this exploration is your roadmap to building legs that don't just look strong—they are strong!

leg extensions, leg curls, squats

Table of Contents: 

  1. Breaking Down The Three Exercises: Pros and Cons
  2. Leg Extensions, Leg Curls vs Squats
  3. Incorporating Leg Exercises Into Your Routine Safely
  4. Frequently Asked Questions
  5. Choosing Between Leg Extensions, Curls, and Squats for Optimal Results

Leg Extensions, Leg Curls, Squats: Differences

Breaking Down The Three Exercises

In this section, we'll dive into the differences and benefits of three popular lower body exercises: leg extensions, leg curls, and squats. We'll explore their key differences and how they can each contribute to a well-rounded leg workout.

Leg Extension

Leg extensions fall into the category of "open chain" exercises, which simply means that during the movement, the end part of the limb in action isn't anchored to a solid surface like the ground.

leg extensions

Leg extensions are a focused exercise targeting the quadriceps at the front of the thigh, particularly the rectus femoris and vastus muscles. This exercise is excellent for enhancing lower body strength and defining muscles, making it a valuable addition to any strength training regimen.

Performed on a leg extension machine, you sit and lift your lower legs by extending your knees against a weighted pad, engaging your quads in the process. Ideal for those aiming to boost their quad strength and size, leg extensions offer a targeted approach to muscle training, allowing for intensive work on specific areas.

They're particularly effective for either wrapping up a session with a targeted burn or prepping your quads for a more extensive workout by pre-exhausting them. As an isolation movement, leg extensions concentrate solely on the quads, setting them apart from exercises that engage multiple muscle groups.


  • Isolate and engage the quadriceps muscles, making them ideal for focused strengthening and muscle building.
  • The controlled movement on a machine minimizes the risk of injury, making it suitable for beginners.
  • Helps in the recovery process for knee injuries by strengthening the muscles around the knee without heavy loading.


  • May not translate as effectively to improved performance in everyday activities or sports that require integrated, whole-body movements.
  • The nature of the movement can put significant stress on the knee joint.

Related: Leg Extension Muscles Worked, Benefits, & More (Complete Guide)

Leg Curls

Hamstring curls, often simply called leg curls, focus on the hamstrings and calves at the back of the leg. This exercise, adaptable to different positions, enhances any lower body strength routine.

leg curls

Performed mainly on a leg curl machine, it involves drawing your heels towards your buttocks while keeping your upper body stationary, effectively strengthening the hamstrings.


  • Leg curls can contribute to knee stability and support, likely reducing the risk of injuries.
  • Leg curl machines are commonly found in gyms, making this exercise easily accessible for many people.
  • Often incorporated into rehabilitation programs for knee and hamstring recovery due to their controlled movement.


  • Leg curls might not offer as much functional benefit as compound movements that mimic everyday activities.

Related: Leg Curl Muscles Worked, Benefits, & More (Complete Guide)


Squats are a fantastic way to strengthen your lower body, not just the quads but also other key muscle groups. With a variety of types like back, front, split, and belt squats, you can target different areas. 


As a comprehensive exercise, squats work the entire posterior chain, especially focusing on the quadriceps and gluteus maximus, with support from the hamstrings.

During a squat, you start from a standing position, bend your knees and hips to lower your body as if sitting back into an invisible chair, then return to standing. This exercise can be performed with body weight alone, or with added resistance such as barbells, dumbbells, or kettlebells.

Pro Tip: 

When squatting, make sure your knees don't extend past your toes and keep your neck straight, focusing on a point directly ahead in the mirror. Avoid looking up or down to prevent neck strain. It's also wise to have a spotter when lifting heavy weights.


  • Engage multiple muscle groups in the lower body, making them highly efficient for building strength, muscle mass, and improving lower body function.
  • Also engage the core muscles, including the abdominals and lower back
  • Mimic natural movements like sitting and standing, improving functional strength that translates into everyday activities and athletic performance.


  • Incorrect squatting technique can lead to knee, back, or other injuries.
  • Limited mobility or flexibility can make achieving proper form challenging.

Leg Extensions, Leg Curls vs Squats

When comparing leg extensions, leg curls, and squats, it's important to understand the variation of each exercise, from the muscles they target to their overall impact on fitness and health.

Differences in Muscle Group Activation

  • Leg Extensions: Focus primarily on the quadriceps, the front thigh muscles, by extending the knee.
  • Leg Curls: Target the hamstrings at the back of the thigh, involving knee flexion to bring the heel towards the buttocks.
  • Squats: Engage a comprehensive range of lower body muscles including quadriceps, hamstrings, glutes, and calves, along with the core for stabilization.

Differences in Application and Effectiveness

  • Leg Extensions: Great for isolating and strengthening the quads, beneficial in rehabilitation settings or for aesthetic muscle development.
  • Leg Curls: Essential for hamstring development, offering balance to the anterior-focused leg extension, with particular use in injury prevention and recovery.
  • Squats: Provide a holistic lower body workout, enhancing functional strength, mobility, and athletic performance.

Squats are a versatile exercise that can be incorporated into a variety of fitness programs. It's from their ability to work multiple muscles, improve functional fitness, and increase overall strength.

Leg extensions and curls are isolation exercises, meaning they focus on single muscle groups, making them best for targeted training and rehabilitation purposes.

Differences in Equipment Used

Leg curl and extension machines

  • Squats: Versatile in equipment needs; can be performed with body weight, free weights, or barbells, accommodating a wide range of environments from gyms to home workouts. This versatility allows individuals to perform squats in various settings, making them a more accessible exercise.

Squats (with resistance bands and barbell)

Differences in Safety and Injury Risk

  • Leg Extensions: Leg extension are much safer, but can place significant stress on the knee joint, especially at higher weights.
  • Leg Curls: Relatively low risk but improper form or excessive weight can lead to hamstring strains.
  • Squats: Demand careful attention to form to avoid lower back and knee injuries, with a higher risk factor due to the compound nature and potential use of heavy weights. Squats put strain on even more joints including the spine, knee, hip, and even the ankles

Mechanical and Kinetic Variations 

  • Leg Extensions: An open kinetic chain exercise focusing on knee extension in a seated position.
  • Leg Curls: Also open kinetic chain, involving knee flexion in a prone or seated position.
  • Squats: A closed kinetic chain movement (feet are in contact with the ground) requiring coordinated flexion and extension of hips, knees, and ankles, engaging the body in a more compound and functional manner.

Differences in Training Approach for Leg Extensions, Leg Curls, and Squats

  • Leg Extensions and Leg Curls: Leg extensions and curls are often used as accessory exercises to supplement compound exercises like squats, or for specialized training and rehabilitation programs focusing on the quadriceps and hamstrings.
  • Squats: Squats can be incorporated as the main lower body component of full-body workout routines or as part of a specific leg day.

Pro tip: 

Leg extensions are superior for targeting quads compared to squats, mainly due to their ability to isolate these muscles. While it is safer, they don't engage gluteus maximus at all. To ensure a well-rounded workout, I recommend incorporating  a glute-specific exercise, like the multi-hip machine, into your routine. 

This is because many of the compound exercises we perform, such as squats  extend the knee and hip simultaneously, which doesn't adequately stress this specific part of our quads. By only doing these compound lifts, it's not fully engaging all four muscles in quadriceps.

Incorporating Leg Exercises Into Your Routine Safely

Incorporating leg extensions, leg curls, and squats into your routine requires careful attention to ensure safety and maximize effectiveness. Here's how to do it:

1. Master Proper Form

  • Leg Extensions: Sit with your back flat against the pad, adjust the pad to rest on your lower shins, just above your feet. Extend your legs fully without locking your knees, then slowly return to the starting position.
  • Leg Curls: Lie face down or sit, depending on the machine, ensuring the pad is just above your heels. Curl your legs up towards your buttocks, keeping your hips firmly on the bench, then slowly lower back down.
  • Squats: Stand with feet shoulder-width apart, toes slightly turned out. Keep your chest up and back straight as you bend your knees and hips to lower down, as if sitting back into a chair, then drive through your heels to return to standing.

2. Picking the Right Weight and Rep Range

Select a weight and rep range that fits your level. For muscle growth in leg extensions, 4 sets of 12-15 reps are effective. Use the RPE scale to gauge effort, aiming for an 8 out of 10, where you could do 2 more reps if pushed.

3. Integrate Gradually

If you're new to these exercises, start by incorporating them once or twice a week into your routine. Allow your muscles to adapt to the new movements to prevent overuse injuries.

4. Balance Your Routine

Combine these exercises with others that work complementary muscle groups to ensure balanced muscle development and prevent imbalances.

For instance, pair leg extensions (which target the quads) with exercises that focus on the hamstrings and glutes.

5. Listen to Your Body

Pay close attention to how your body responds during and after these exercises. Mild muscle soreness is normal, but sharp pain, especially in the joints, is a sign you may need to adjust your form, reduce the weight, or take a break.

6. Prioritize Recovery

Ensure you have enough rest between workout sessions targeting the same muscle group. Recovery is crucial for muscle repair and growth.

7. Warm-Up and Cool Down

Begin each session with a warm-up to prepare your muscles and joints, and conclude with a cool-down period, including stretching to aid in recovery and flexibility.

8. Adjust for Personal Needs

Be mindful of any existing conditions or injuries, especially related to the knees or lower back, and modify these exercises as needed.

For example, those with knee issues may need to limit the range of motion in squats or use alternative exercises.

Pro Tip: 

I always start my workouts with compound movements like squats before moving on to isolation exercises such as leg extensions. This approach works well for me because compound exercises work multiple muscle groups at once and really ramp up my overall effort.

By tackling squats first, I'm able to use my peak strength and energy where it counts the most, and then I follow up with leg extensions to zero in on my quadriceps. This strategy ensures that I'm not missing out on fully developing my quads, especially since squats alone don't thoroughly work all four quad muscles.

    Frequently Asked Questions

    Why are leg extensions a better quad exercise than squats?

    It's evident that leg extensions, as straightforward knee extension exercises, effectively stimulate and develop all the knee extensor muscles. In contrast, squats primarily target the vasti muscles – specifically the vastus medialis and vastus lateralis. Notably, leg extensions are particularly beneficial for enhancing the vastus lateralis, the outer quad muscle that contributes to the desirable 'quad sweep.'

    Is leg extension better than hack squat?

    Leg extensions isolate the quadriceps, making them great for targeted muscle building. Hack squats, being a compound movement, engage multiple leg muscles, including quads, glutes, and hamstrings, offering a more comprehensive lower body workout. Choose based on whether you aim for specific quad strengthening or overall leg development.

    Are leg curls the same as squats?

    No, leg curls and squats are not the same. Leg curls are an isolation exercise that primarily targets the hamstrings by bending the knee to bring the heel towards the buttocks. Squats are a compound exercise that engages multiple muscle groups, including the quadriceps, hamstrings, glutes, and core, by bending at the hips and knees to lower the body as if sitting back into a chair, then standing back up.

    Choosing Between Leg Extensions, Curls, and Squats for Optimal Results

    As we wrap up our deep dive into the trio of leg day heroes—leg extensions, leg curls, and squats—it's clear that each brings its own flavor to the feast of strength.

    Whether you're etching out definition with the precision of leg extensions and curls or conquering the mighty squat, the journey to formidable lower-body strength is as varied as it is rewarding.

    Remember, the ultimate leg workout doesn't hinge on choosing one exercise over the others; it's about how you blend these moves to suit your goals, challenge your limits, and evolve your fitness journey.

    So, the next time you lace up for leg day, armed with the knowledge of what each exercise offers, you're not just stepping into the gym—you're crafting the very foundation of your strength, rep by rep. Here's to the burn, the triumphs, and the ever-rising peaks of your leg day adventure!

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    About The Author

    Matt Gemkow, the author of this content section at Select Fitness USA, boasts more than 15 years of fitness experience. He started out in sports and athletic training for many years and has since 2014 transitioned into heavy-weight training and bodybuilding. As a result, he has become one of the most experienced fitness equipment experts out there, and a valuable source of information.