Leg Extension Machine

As an open-kinetic chain exercise, the leg extension machine features a single-jointed movement that serves as a vehicle for unadulterated quadricep isolation. This is accomplished via knee extension (straightening your leg) against resistance. 

Leg extensions help build stronger, denser quadriceps muscles. They are easily programmed into various exercise routines and are appropriate for all fitness levels, from beginners to more advanced lifters.

The leg extension machine is a popular resistance training machine found in virtually all commercial gyms.

How To Do

  1. Seat yourself in the machine with your knees at a 90-degree angle. The shin pad should rest at your ankles with your feet facing forward.
  2. Grip the hand bars on both sides of the machine while maintaining a neutral spine and engaged core. Adjust the machine as needed.
  3. Use your quadriceps to lift the weight upwards until your legs are nearly straight but not locked out or hyperextended.
  4. Slowly release and return to the 90-degree starting position.

Tips From Expert

  • Alternate with the leg curl machine for maximum hypertrophic and metabolic benefits. This is called a superset, which is when you complete two exercises back-to-back with minimal rest in between sets. 
  • Slow down and focus on the mind-muscle connection, which has been shown to improve muscle hypertrophy. The leg extension machine does not rely on balance or multiple joints, so you should feel this exercise solely in your quadriceps.
  • To avoid relying on momentum or gravity, focus on a slow, controlled tempo throughout the exercise. A brief pause at the top and bottom can further assist with this.

Optimal Sets and Reps

The leg extension machine can be easily incorporated into a variety of different training modalities. The graph below illustrates the optimal ranges for sets and reps to best align with your specific training style.

Training Type Sets Reps
Strength Training 3–4 6–12
Hypertrophy 3–4 12–15
Endurance Training 2–3 15+
Power Training 3–4 6–8
Optimal Sets & Reps of Leg Extension Machine

How to Put in Your Workout Split

The leg extension machine can be added to your workouts as an isolation exercise for effective, concentrated quadriceps activation. Due to its isolative nature and stable environment, it should be programmed after compound lifts (squats, deadlifts). It requires less energy and total body muscle recruitment. 

  • Hypertrophy Training Splits — Add this exercise to your leg workouts after your compound lifts. It pairs nicely alongside other isolation exercises, such as leg curls, and just before a cool-down workout.
  • Strength and Power Training — Utilize the leg extension machine as an accessory movement. Program the exercise after your compound movements. Aim to lift at 80% of your 1 rep max (1RM) to help develop strength.
  • Endurance Training — Add a strength-focused day that includes the leg extension machine once or twice a week for optimal endurance and strength gains. As endurance training features a higher training volume, choose a weight that allows you to complete at least 15 reps.

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Equipment

Leg Extension Machine

This is a great piece of equipment to strengthen your quads and provide a rehabilitation exercise. A good alternative exercise would be sissy squats.

Who Should Do?

Gymgoers Looking To Increase Quadriceps Strength And Size

The leg extension machine provides an exclusive quadricep workout with considerable muscle stimulation. This exercise mimics the primary function of the quadriceps and helps them grow stronger and denser. It is also one of the best exercises for building up the rectus femoris, one of the four quadriceps muscles. 

Those With Poor Balance

If you are looking for quadricep exercises but struggle with maintaining proper balance, consider the leg extension machine. It allows for excellent muscle activation in a seated environment. By taking balance out of the equation, injury risk is reduced. 

*Expert Tip: Pair this exercise with other stable isolation movements, like leg curls, for more comprehensive lower body muscle recruitment.

Beginners

Due to its simplicity, the leg extension machine is especially complementary to a beginner’s workout. This isolation movement is completed on a stable machine, allowing you to focus solely on knee extension. 

Research has shown that resistance training helps develop strength in untrained individuals. The leg extension machine is a great way to get started.

Who Should Not Do?

Existing Knee Injuries

Avoid the leg extension machine if you suffer from a knee injury. This exercise may not be the best choice due to the strain it places on the knee. Those with injuries may also be unable to achieve optimal quadriceps muscle activation, which will hinder your results. If your knee is injured, consult with your doctor before adding leg extensions to your workout.

Gymgoers Pressed For Time

Individuals looking to narrow down their training time would benefit from focusing on compound, multi-joint exercises instead of isolation exercises. While very effective at quadricep activation, the leg extension does not hit multiple joints or muscle groups at once. If you are pressed for time, choose compound, functional exercises such as a squat.

Individuals With Tight Quadricep Muscles

When muscles are tight, they need to be stretched. When muscles are weak, they need to be strengthened. Individuals with tight quadriceps may find the large knee extension and flexion movement patterns hard to perform.

Stretching can help improve the quadriceps’ range of motion and prevent strains. Once quadriceps tightness has resolved, consider incorporating strengthening exercises such as leg extensions.

Benefits Of The Leg Extension Machine

Builds Strength 

When muscles work against resistance, they grow stronger in response to the training stimuli provided. If building strength in the quadriceps is your primary goal, the leg extension machine can help. It provides an environment to perform knee extension with minimal risk of other muscle groups overcompensating.

Improves Athletic Performance 

Athletes who participate in jumping and running motions require strong quadriceps for optimal performance. 

As the majority of quadricep injuries appear to occur during preseason, athletes should strive to achieve and maintain year-round quadricep strength. The leg extension machine is a great option for athletes looking to target their quadriceps. 

Prevents Injuries

Weak quadriceps may increase your risk of lower extremity injury. Strengthening this large muscle group is an ideal strategy for reducing injury risk. Combine this exercise with other compound and isolation movements to help develop total body strength.

In the case of existing injuries, open-kinetic chain exercises such as the leg extension machine provide favorable outcomes in rehabilitation protocols. 

If you are suffering from injury, obtain medical clearance prior to participating in this exercise.

Frequently Asked Questions

What is a leg extension machine good for?

A leg extension machine is good for isolating the quadriceps. You do not need to worry about other muscles overcompensating during isolation movements. It is complementary to a variety of different routines, as seen in this 3-day workout split guide.

What are the disadvantages of leg extensions?

As a single-jointed movement, the leg extension’s narrow focus may aggravate existing injuries or tightness. Additionally, the isolation restricts muscle activation to the quadriceps only. There are better options for a more total-body approach to exercise selection.

Should you go heavy on leg extensions?

Yes! The leg extension offers a stable working environment and an isolated burn, making it a prime candidate for heavy lifting. For maximal gains, work to failure or just short of failure with an appropriate weight that does not compromise form.

How often should you do leg extensions?

Strength and muscle growth occur during the recovery phase. Allow yourself 2–3 days of adequate quadricep rest in between the days you complete leg extensions for maximal benefits.

Resources

Endomondo.com refrains from utilizing tertiary references. We uphold stringent sourcing criteria and depend on peer-reviewed studies and academic research conducted by medical associations and institutions. For more detailed insights, you can explore further by reading our editorial process.

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