Instructions
- Adjust the back pad so you can lean back at about a 30-degree angle, and scoot your butt forward so your knees are just in front of the edge of the seat when you’re seated.
- Then adjust the shin pad so it touches your shins right above your ankles and puts your feet as close to your butt as possible. If the machine has a thigh pad as well, adjust it so it’s snug when seated but not painful.
- Grab the handles and push your feet toward the ceiling as hard as you can until your legs are straight, and hold this position for a brief moment.
- Lower your feet under control and return to the starting position.
Expert Tips
- Leaning back puts the rectus femoris in a more stretched position, which may be better for muscle growth, improves bloodflow to the quads, and is more comfortable for most people. Depending on what machine you’re using, this may mean that only your shoulders and upper back are touching the back pad, which is fine. Some people refer to this as the “lay-back leg extension.”
- Squeeze as hard as you can at the top of each rep to ensure you’re using the full range of motion, and lower the weight under control (don’t relax your legs and let the weight stack slam down). If you aren’t used to training this way, you’ll probably need to reduce the weight.
- Avoid letting the weight stack rest at the bottom of each rep. This keeps tension on your quads throughout the entire set.
- Try to minimize upper body movement—ideally, only your lower legs are moving.
Workout Programming
If you’re using the leg extension to give your quads more volume after another quad exercise like the squat or leg press, it’s often best to program it as the third exercise in your workouts. First you do a squat variation, then a hamstring exercise (to rest your quads), and then hit your quads again with the leg extension.
If you’re using the leg extension as your primary quad exercise, and you want to focus on growing your quads, you can also do it as the first exercise in your leg or lower-body workouts.
A good default is 3 sets of 6–8 or 8–10 reps. Take each set 1–2 reps shy of failure and rest 1–2 minutes between sets. Allowing enough rest helps you maintain your performance across sets.
Mike’s Take
The leg extension is my favorite quad isolation exercise for several reasons:
First, it allows you to isolate the quads. Unlike compound exercises, like the squat, the leg extension doesn’t rely on any other supporting muscle groups.
When you hit failure on a set of leg extensions, you know it was your quads that failed and not some other muscle group (like your low-back during squats). It also isn’t limited by your cardiovascular fitness or grip strength the way the Bulgarian split squat or dumbbell lunge are.
This also makes it an excellent way to keep training your quads after your low-back is already fried from squats, deadlifts, playing with your kids, or some other exercise or activity.
Second, it effectively trains every portion of the quads. The quads are made up of the vastus lateralis, vastus medialis, the vastus intermedius, and the rectus femoris.
Research shows leg extensions produce more growth in the rectus femoris—the quad muscle that goes down the center of your thigh and connects to your pelvis—than leg presses, and it’s safe to assume this applies to similar exercises like squats and hack squats, too.
In a study conducted by researchers at Ritsumeikan University, 17 untrained adults trained one leg with leg extensions and the other with leg presses twice a week for 12 weeks.
The rectus femoris grew by 13.2% in the leg-extension leg, compared with 1.1% in the leg-press leg. Growth in the other three quad muscles was similar, while the leg press produced more growth in the glutes and adductor magnus, a large inner-thigh muscle.
Research shows you can further emphasize the rectus femoris during leg extensions by leaning back instead of sitting upright.
In a study conducted by researchers at Nord University, 22 untrained men did leg extensions for 10 weeks with one leg at a time. One leg trained with the hip bent at 40 degrees (leaning back) and the other at 90 degrees (sitting upright).
The leg trained in the reclined position gained 12.4% in muscle thickness near the top of the rectus femoris (near the hip), versus 4.6% in the leg trained in the upright position. Near the lower end of the rectus femoris (near the knee), the increases were 15.8% and 10.9%.
Growth in the vastus lateralis—the large quad muscle on the outside of your thigh—was similar in both positions.
Third, leg extensions require very little coordination or motivation to do. This makes it easy for beginners to learn and easier to confront than a set of squats when you’re already feeling ragged.
It’s still a very challenging exercise when taken close to failure, but it’s not as daunting as a hard squat workout. This also makes them safer to perform than squats when you’re fatigued.
Fourth, you can safely take leg extensions all the way to muscular failure, which isn’t the case on squats and most other compound lower-body exercises (it’s a little iffy even on leg press).
And as a general rule, the closer you train to failure, the more tension your muscles will be forced to produce, and the more muscle you’ll grow.
Now, I’m still a big fan of squats. For most people, they’re an outstanding way to train your quads, adductors, glutes, and lower back, which is why I include them in both of my programs for men and women, Bigger Leaner Stronger and Thinner Leaner Stronger.
That said, it’s worth acknowledging that squats do have some drawbacks and that leg extensions have several important advantages. Of course, you can always do both, which is what I recommend for most people.
The leg extension does have a reputation for irritating people’s knees, but this is mostly due to user error. Most people use far too much weight, progress too quickly, do too much volume, and use bad technique, which is a recipe for joint pain on any exercise.
I’d wager another reason for their bad rap is that far more people do the leg extension than squats or leg press, because it looks like a more approachable, beginner friendly exercise.
All in all, leg extensions are perfectly safe for your knees so long as you use proper form, appropriate volume and intensity, and progress gradually.
Leg Extension Alternatives
- Single Leg Extension. This variation allows you to fix any muscle or strength imbalances you might have, but it also takes twice as long to complete each set. Unless you’re sure you have a meaningful strength disparity between your legs (most people don’t), stick with the regular leg extension.
- Leg Press. The leg press also emphasizes your quads without putting much stress on your lower back, and has the added benefit of training your glutes and adductors. That said, it doesn’t target the rectus femoris as well as the leg extension.
- Hack Squat. Another great quad exercise that isn’t limited by your lower-back strength and that also trains your glutes. You can program this interchangeably with the leg press.
- Belt Squat. This is a squat movement performed with a heavy weighted belt instead of a barbell. It also trains the quads, adductors, and glutes without being limited by your lower-back strength, but it can be easier to cheat (by leaning forward or backward) and is more exhausting than the leg extension. Plus, most gyms don’t have one.
- Pendulum Squat. This is basically a hack squat that allows your body to move in a more natural range of motion and has a better resistance curve. It’s one of the most comfortable and joint-friendly lower body machines that allows you to safely push as close to failure as you’d like. Sadly, most gyms don’t have one.
3 Leg Extension Workouts
Here are three sample workouts that show how to program the leg extension in a leg/lower-body workout, a quad-focused workout, and a full-body workout.
Leg/Lower Body Workout with the Leg Extension
Barbell Back Squat: 3 sets | 4–6 reps | 2–3 min rest
Barbell Romanian Deadlift: 3 sets | 4–6 reps | 2–3 min rest
Leg Extension: 3 sets | 6–8 reps | 1–2 min rest
Seated Leg Curl: 3 sets | 6–8 reps | 1–2 min rest
Standing Calf Raise: 2 sets | 8–10 reps | 1–2 min rest
Quad-Focused Leg Workout with the Leg Extension
Leg Extension: 3 sets | 6–8 reps | 1–2 min rest
Seated Leg Curl: 3 sets | 6–8 reps | 1–2 min rest
Leg Press: 3 sets | 6–8 reps | 1–2 min rest
Lying Leg Curl: 3 sets | 6–8 reps | 1–2 min rest
Standing Calf Raise: 2 sets | 8–10 reps | 1–2 min rest
Seated Calf Raise: 2 sets | 8–10 reps | 1–2 min rest
Full-Body Workout with the Leg Extension
Barbell Bench Press: 3 sets | 4–6 reps | 2–3 min rest
Chest-Supported Row: 3 sets | 6–8 reps | 2–3 min rest
Leg Extension: 3 sets | 6–8 reps | 1–2 min rest
Seated Leg Curl: 3 sets | 6–8 reps | 1–2 min rest
Barbell Curl: 2 sets | 6–8 reps | 1–2 min rest
Cable Side Raise: 3 sets | 8–10 reps | 1–2 min rest
To progress these workouts, use double progression: use a weight that allows you to work within the given rep range, take each set 1–2 reps shy of failure, and once you hit the top of the range for your first set, add weight.
Muscles Worked by the Leg Extension
The leg extension primarily trains the quadriceps, or “quads,” on the front of your thighs:
- Rectus femoris
- Vastus lateralis
- Vastus medialis (which includes the vastus medialis oblique, or “VMO”)
- Vastus intermedius
More Quad Exercises