Leg Extension
The Leg Extension primarily works the Rectus Femoris, Vastus Lateralis, Vastus Medialis, with secondary activation of the Vastus Intermedius and stabilizer support from the Rectus Abdominis. It is a machine isolation exercise at beginner difficulty.
The Leg Extension is an beginner isolation exercise performed with machine, following a extension movement pattern. It primarily targets the Rectus Femoris, Vastus Lateralis, Vastus Medialis, with secondary engagement of the Vastus Intermedius. This is a bilateral pushing movement, meaning both sides work together to generate force.
Machine leg extension extending knees emphasizing quadriceps.
| Equipment | Machine |
|---|---|
| Difficulty | Beginner |
| Type | Isolation |
| Movement | Extension |
| Force | Push |
| Laterality | Bilateral |
| Primary | Rectus Femoris, Vastus Lateralis, Vastus Medialis |
| Secondary | Vastus Intermedius |
Muscles Worked
The Rectus Femoris, Vastus Lateralis, and Vastus Medialis are the primary movers, collectively driving the movement and absorbing the greatest share of the load. The Vastus Intermedius assists as a secondary mover, contributing to force production without bearing the primary load. The Rectus Abdominis act as stabilizers, maintaining joint position and postural alignment throughout the movement.
Primary Muscles
- Primary Muscle Rectus Femoris (quadriceps)
- Primary Muscle Vastus Lateralis (quadriceps)
- Primary Muscle Vastus Medialis (quadriceps)
Secondary Muscles
- Secondary Muscle Vastus Intermedius (quadriceps)
Stabilizer Muscles
- Stabilizer Muscle Rectus Abdominis (core)
How to Perform
Preparation
- Adjust machine seat and pads to fit body.
- Sit or position body in machine.
Execution
- Extend through full range of motion against resistance.
- Return to starting position under control.
- Repeat.
Comments
- Maintain control throughout movement to fully engage the Rectus Femoris, Vastus Lateralis, Vastus Medialis.
Tips & Common Mistakes
- Fully extend through the range of motion to achieve peak muscle contraction.
- Avoid hyperextending the joint at end range — stop just short of lockout.
- Control the return to take full advantage of the eccentric stimulus.
Programming Suggestions
Adapt your sets and reps to your training goal. As a beginner-friendly exercise, start with lighter loads and focus on form before progressing weight.
| Strength | 3–4 sets × 6–8 reps at 75–85% 1RM with 90–120 seconds rest. |
|---|---|
| Hypertrophy | 3–4 sets × 10–15 reps at 60–75% 1RM with 60–90 seconds rest. |
| Endurance | 2–3 sets × 15–25 reps at 40–60% 1RM with 30–45 seconds rest. |
Alternative Exercises
These exercises target the same primary muscles (Rectus Femoris, Vastus Lateralis, Vastus Medialis) and can be substituted based on your equipment or variation preferences.
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