Machine Leg Extension
Also known as: leg extension
- Secondary muscles
- Hamstrings
- Body part
- Upper Legs
- Position
- Seated
- Laterality
- Bilateral (both sides together)
- Category
- Strength
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No other common movement isolates the quads the way the leg extension machine does: with the hips fixed and the pad at your shins, straightening the knees is the only way to move the weight. Squats and presses never fully load the final degrees of extension, and that top range is exactly where this machine earns its keep.
How to do the Machine Leg Extension
- Adjust the seat height and backrest of the machine to fit your body.
- Sit on the machine with your back against the backrest and your feet on the footpad.
- Grasp the handles or sidebars for stability.
- Extend your legs forward by straightening your knees, lifting the weight.
- Pause for a moment at the top, then slowly lower the weight back to the starting position.
- Repeat for the desired number of repetitions.
Tip: Point the toes slightly up and pause at the top of every rep.
Muscles worked
Primary
Quads · Legs
The quads straighten the knee against the pad and should feel a hard contraction at the top and a burn through the front of the thigh by the end of the set.
Secondary
Common mistakes
- Swinging the legs up — the weight should rise under control with a pause at the top, not kick up with momentum.
- Sitting too far forward — the knee should line up with the pivot point of the machine, so adjust the seat back until it does.
- Dropping the weight down — lower for three seconds and stop just before the stack touches to keep tension on the quads.
- Only doing partial reps — go to full lockout at the top and squeeze the quad hard for a count.
Where it fits in a workout
Leg extensions go after squats or leg press as a quad accessory, or before them as a warm-up with light weight. Superset them with leg curls on the neighboring machine.
How many sets, how heavy and how hard: see what the ACSM position stands support.
Variations and alternatives
Similar exercises
Without machine
When to talk to someone
- Chest discomfort, feeling faint or lightheaded, or trouble breathing during or after exercise can be signs of a heart attack. In the US, call 911 right away; elsewhere, call your local emergency number.
- Heart, metabolic or kidney disease, or symptoms like these when you are active: talk to your doctor before you start or step up training.
- Pregnant: ask your obstetric care provider which exercise suits you.
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More exercises
Sources
- ACSM position stand on exercise quantity and quality (Garber et al., 2011)
- ACSM preparticipation health screening (Riebe et al., 2015)
- ACOG Committee Opinion No. 804 on exercise in pregnancy (2020)
- CDC: About Heart Attack Symptoms, Risk, and Recovery (2024)
Sources checked on October 17, 2026. Full citations are in the exercise library.
Animation and exercise data: ExerciseDB, licensed to SetGrip. General information, not medical or coaching advice.