Leg Extension


Leg Extension

A leg workout is not complete without a few hard-fought reps on the leg extension machine. Leg extension isolates the quads – one of the biggest muscle group in your body – and  can produce outstanding definition in your thighs. Quads work to straighten the knees, so this exercise can help protect your knees or assist with rehabilitation after a knee injury. A leg extension machine can work each leg individually or both legs together.

Machine Leg Extension Proper Technique

STARTING POSITION (SETUP): Select a weight from the stack and adjust the back of the seat so that the axis of the machine is in line with your knees. Adjust the shin pad so that it is just above your ankles. Your knees should be bent 90 degrees or more, with your toes pointing in front of you. Grasp the handles firmly, with your torso upright, your back against the pad, and your hips pulled down securely into the seat.

Leg Extension

Leg Extension

MOVEMENT (ACTION): Grab the handles on either side of the seat for support, then raise your lower legs up (extend your knees) in a semicircular motion until your legs are straight and can’t go any higher (until your legs are parallel to the ground). Your toes are pointing directly upward during the movement. Pause for a second in the contracted position before lowering the weight down slowly to the starting position.

Machine Leg Extension Tips & Key Points

  • Look for only your lower legs to move: the entire rest of your body should remain stationary;
  • Don’t let your back move forward or your buttocks come off the seat during the movement;
  • Be sure that your thighs, lower legs, and feet are parallel to each other;
  • Control the movement in both directions;
  • Avoid allowing any space between the back of your knees and the seat edge;
  • Avoid any spinal movement whatsoever;
  • Avoid elevating your shoulders;
  • Avoid allowing your hips or gluteals to elevate off the seat;
  • Maintain an upright torso – right against the seat back;
  • Never “kick” up the weight up in a jerky manner;

Leg Extension Exercise Video Demonstration

This short instructional video will demonstrate you how to perform leg extension exercise using perfect technique so you can get maximum results.

Leg extension variations

  • One-leg extension. Performing this exercise one leg at a time improves focus. The unilateral leg extension is particularly useful for improving thigh asymmetry or aiding in rehabilitation when one leg is injured.
  • Another helpful technique is to vary leg/foot position. These variations create different recruitment patterns for muscles, thereby producing the most complete workout possible for the leg extension. For example, turning your feet (toes) slightly out (targeting the vastus medialis) or slightly in (targeting the vastus lateralis) will work the quads in a functionally different way. Pointing your toes directly upward hits all sections of the quadriceps equally.

Muscles Involved in Leg Extension

Main muscles: quadriceps (vastus internus, externus, intermedius)
Secondary muscles: front quadriceps, gluteal deltoid (tensor fasciae latae and superficial fibers of the gluteus maximus)
Antagonists: hamstrings, biceps femoris (short head), gracilis, sartorius, gastrocnemius

Machine Leg Extension Replacement Exercises

  • Barbell squat
  • Dumbbell squat
  • Front barbell squat
  • Leg press
  • Hack squat
  • Step-up


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