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Leg Extension 101 Video Tutorial

Gym Main Variation Strength


Leg Extension
Leg Extension

Exercise Synopsis

Target Muscle Group


Secondary Targets



Force Type

Push (Bilateral)

Required Equipment

Leg Extension Machine

Fitness Level












The Leg Extension is an isolation exercise specifically designed to target the quadriceps, making it a fundamental component of lower body strength training. Executed on a Leg Extension Machine, this exercise involves extending the knees against resistance, activating the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius—the four muscles that collectively form the quadriceps. The Leg Extension provides a focused and controlled movement, isolating the quads to promote muscle hypertrophy and enhance strength in the front of the thigh. While primarily targeting the quads, the exercise also engages the serratus muscles to a lesser extent. The Leg Extension is valued for its ability to isolate the quadriceps, aiding in muscle development, and is commonly incorporated into leg workout routines for individuals seeking to strengthen and define their lower body.

How to Perform

  1. Set the preferred resistance on the weight stack by inserting the pin, customizing the intensity to your fitness level.

  2. Align the seat so that your knees are directly in line with the machine's axis, optimizing the biomechanics of the Leg Extension exercise.

  3. Sit on the machine and place your shins securely behind the pad located at the machine's base, ensuring stability throughout the movement.

  4. Inhale deeply and initiate the exercise by extending your legs, contracting the quadriceps to maximize engagement of the target muscle group.

  5. Exhale as you reach the full extension, locking out the knees at the peak of the repetition to emphasize the contraction of the quadriceps.

  6. With controlled movements, slowly lower your feet back to the starting position, maintaining proper form and preventing abrupt or jerky motions.

  7. Repeat the sequence for the desired number of repetitions, emphasizing a smooth and controlled execution for optimal muscle activation.


  1. Confirm that the axis of rotation for the knee aligns precisely with that of the Leg Extension Machine. Ensuring this alignment is critical as it maintains a direct line with the knee joint, minimizing unnecessary stress on the joint and reducing the risk of injury. Incorrect positioning, where the knee is either too far forward or behind the axis of rotation, may lead to excessive joint stress.

  2. Recognize that Leg Extensions are generally most effective when performed with moderate rather than excessively heavy weights. This recommendation stems from the fact that Leg Extensions lack hamstring co-contraction with the quads. Excessive weight during isolated quad exercises may increase the risk of knee injury. Prioritize controlled and moderate resistance to promote muscle engagement without compromising safety.

  3. Experiment with pointing your toes during Leg Extensions as it can potentially enhance the mind-muscle connection. This subtle adjustment may contribute to increased awareness and activation of the quads during the exercise, optimizing the overall effectiveness of the Leg Extension.

How Not to Perform

  1. Avoid Incorrect Seat Positioning: Do not position the seat of the Leg Extension Machine in a way that misaligns the axis of rotation with your knee joint. Incorrect alignment could lead to increased stress on the knee joint and the risk of injury. Ensure that the axis of rotation directly matches that of your knee for proper biomechanics.

  2. Steer Clear of Excessive Weight: Refrain from using excessively heavy weights during Leg Extensions, as these can pose a risk due to the lack of hamstring co-contraction. Using weights that are too heavy may increase the likelihood of injury, particularly to the knee joint. Opt for a controlled and moderate weight that allows for proper muscle engagement without compromising safety.

  3. Avoid Rapid or Jerky Movements: Prevent executing Leg Extensions with rapid or jerky movements. Swift motions not only reduce the effectiveness of the exercise but can also lead to improper form, increasing the risk of injury. Prioritize controlled and deliberate movements to maximize muscle engagement and minimize the risk of strain.

  4. Do Not Neglect Full Range of Motion: Avoid limiting the range of motion during Leg Extensions. Failing to extend fully or lowering the weight too quickly can reduce the effectiveness of the exercise. Ensure that each repetition involves a complete extension and controlled descent to fully activate the quads.

  5. Refrain from Pointing Toes Inward: Do not point your toes inward during Leg Extensions, as this can alter the muscle engagement pattern and potentially lead to imbalances. Maintain a neutral foot position to ensure the quads are the primary focus and to avoid unnecessary stress on the knee joint.

  6. Avoid Using Momentum: Steer clear of using momentum to lift the weight. Utilizing momentum diminishes the isolation of the quads and reduces the energy directed to the target muscle group. Instead, focus on a steady and controlled lifting and lowering motion to optimize muscle engagement.

  7. Do Not Neglect Core Activation: Avoid neglecting your core muscles. Failing to engage the core can compromise stability and reduce the effectiveness of the exercise. Maintain a tight core throughout the movement to support proper form and enhance overall control.

  8. Avoid Overarching the Lower Back: Do not arch your lower back excessively during Leg Extensions. Overarching can lead to unnecessary strain on the lumbar spine and detract from the isolation of the quads. Keep your lower back in a stable and neutral position throughout the exercise.


Variations of fitness exercises refer to different ways of performing a specific exercise or movement to target various muscle groups, intensities, or goals. These variations aim to challenge the body differently, prevent plateaus, and cater to individuals with varying fitness levels.


Alternative exercises in fitness refer to different movements or activities that target similar muscle groups or serve the same training purpose as the primary exercise. These alternative exercises can be used as substitutes when the original exercise is unavailable or challenging to perform due to various reasons such as equipment limitations, injuries, or personal preferences.


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