How to Do Leg Extensions
Start and end of one clean rep of Leg Extensions.
Quick facts
| Primary muscle | Quads |
|---|---|
| Secondary muscles | — |
| Equipment | Machine |
| Category | Strength |
How to perform Leg Extensions
- For this exercise you will need to use a leg extension machine. First choose your weight and sit on the machine with your legs under the pad (feet pointed forward) and the hands holding the side bars. This will be your starting position. Tip: You will need to adjust the pad so that it falls on top of your lower leg (just above your feet). Also, make sure that your legs form a 90-degree angle between the lower and upper leg. If the angle is less than 90-degrees then that means the knee is over the toes which in turn creates undue stress at the knee joint. If the machine is designed that way, either look for another machine or just make sure that when you start executing the exercise you stop going down once you hit the 90-degree angle.
- Using your quadriceps, extend your legs to the maximum as you exhale. Ensure that the rest of the body remains stationary on the seat. Pause a second on the contracted position.
- Slowly lower the weight back to the original position as you inhale, ensuring that you do not go past the 90-degree angle limit.
- Repeat for the recommended amount of times.
Muscles worked
- Quads (primary): extends the knee to drive squats, lunges and jumps.
Sets & reps by goal
| Goal | Sets × reps | Load | Rest |
|---|---|---|---|
| Strength | 3–5 × 3–5 | Heavy (~85%+) | 2–3 min |
| Hypertrophy | 3–4 × 8–12 | Moderate (~65–75%) | 60–90 s |
| Endurance | 2–3 × 15–20 | Lighter (~50–60%) | 30–45 s |
Pick the row that matches your goal. If you're newer, anchor in the hypertrophy range while you groove the form.
Form tips
- Keep the knees tracking in line with the toes and push the whole foot into the floor.
- Set the seat and pads so the machine's pivot lines up with the joint you're training before your first rep.
- Treat every rep the same — a repeatable setup and bar path is what lets you add weight safely over time.
- Breathe out on the effort and in on the return, keeping one steady rhythm across the set.
Common mistakes
- Letting the knees cave inward as you push out of the bottom.
- Leaving the seat or range on a setting that forces the joint into an awkward angle.
- Chasing weight jumps before the current load feels solid on every rep.
Frequently asked questions
What muscles does Leg Extensions work?
Leg Extensions is a focused movement that primarily works the quads.
What equipment do I need for Leg Extensions?
Leg Extensions needs the corresponding weight-stack or plate-loaded machine.
How many sets and reps should I do for Leg Extensions?
It depends on your goal: about 3–5 sets of 3–5 heavy reps for strength, 3–4 sets of 8–12 for muscle growth, or 2–3 sets of 15–20 for endurance. Pick the row that matches your goal. If you're newer, anchor in the hypertrophy range while you groove the form.
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