QuadsMachineBeginner

How to Do Leg Extensions

By Bryan Alger, Co-Founder of Gravitus

· Updated Sep 30, 2026

A leg extension is a machine exercise that trains the quads on their own. Sit with your knees lined up with the pivot and the pad just above your ankles, then straighten your legs all the way and lower under control. It works all four quad muscles. Most lifters do 3 to 4 sets of 10 to 15 reps.

Sets x reps 3-4 x 10-15

Median 10-rep weight 15570 lbkg men 9040 lbkg women

Muscles Quads, the rectus femoris most

Setup Knee on the pivot, pad above the ankle

1Bottom. Knees lined up with the machine's pivot, pad just above your ankles, back on the pad and hands on the handles.
2Top. Straighten your knees all the way and hold for a second, then lower over 2 seconds without letting the plates touch.

Watch 3 video demonstrations

Video 1 of 3

Find more video demonstrations in the Gravitus app

Technique

How to do a leg extension

Sit down and move the backrest until the backs of your knees touch the front of the seat and your knees line up with the machine's pivot, usually marked with a dot.
Set the shin pad just above your ankles. If the machine sets the start angle, pick the deepest position that feels comfortable.
If the backrest reclines, lean it back. Hold the handles so your hips stay down on the seat.
Straighten your knees all the way and hold the top for a second.
Lower over 2 seconds until your knees are fully bent, without letting the plates touch, and go again.

Setup

Lean the backrest back

Backrest reclinedMore rectus femorisYour hip opens, which stretches the one quad muscle that crosses the hip. It grew more this way.

Backrest uprightSame other quadsThe vastus muscles grew the same whether the seat was reclined or upright.

Knee on the pivotPad stays putWith your knee off the pivot, the pad rolls along your shin through the rep.

Pad above the ankleFeet relaxedLow on the shin, above the ankle joint, so the pad pushes on bone, not your foot.

The rectus femoris is the only quad muscle that crosses the hip as well as the knee, so how far you lean back changes how stretched it is. Twenty-two untrained men trained one leg reclined, with the hip bent 40 degrees, and the other sitting upright at 90 degrees for 10 weeks. The rectus femoris grew more on the reclined leg and the vastus lateralis grew the same on both (Larsen 2025). If your backrest does not recline, sitting upright still trains the quads well.

Gravitus data

How much weight should you leg extend?

On Gravitus, the median man lifts 155 lb (70 kg) for 10 reps on the leg extension, and the median woman 90 lb (40 kg).

Men, typical 155 lb for 10 reps

Most lift: 110 to 200 lb
Top 10% lift: 245 lb or more
Starting out: under 110 lb

Women, typical 90 lb for 10 reps

Most lift: 60 to 120 lb
Top 10% lift: 155 lb or more
Starting out: under 60 lb

Men, typical 70 kg for 10 reps

Most lift: 50 to 90 kg
Top 10% lift: 110 kg or more
Starting out: under 50 kg

Women, typical 40 kg for 10 reps

Most lift: 27.5 to 52.5 kg
Top 10% lift: 70 kg or more
Starting out: under 27.5 kg

One-rep max / 10-rep weight, rounded to 5 lb (2.5 under 40). From 24,410 men and 7,925 women who log the leg extension on Gravitus, computed Sep 29, 2026 (Brzycki). Methodology
Percentile	Men	Women
25th	145 / 110 lb	80 / 60 lb
Median	205 / 155 lb	120 / 90 lb
75th	265 / 200 lb	155 / 120 lb
90th	325 / 245 lb	205 / 155 lb

One-rep max / 10-rep weight, rounded to 2.5 kg (1 under 20). From 24,410 men and 7,925 women who log the leg extension on Gravitus, computed Sep 29, 2026 (Brzycki). Methodology
Percentile	Men	Women
25th	67.5 / 50 kg	37.5 / 27.5 kg
Median	92.5 / 70 kg	52.5 / 40 kg
75th	120 / 90 kg	72.5 / 52.5 kg
90th	147.5 / 110 kg	92.5 / 70 kg

Leg extension numbers only compare on the same machine. Cams, lever lengths and plate-loaded levers differ between brands, so the same pin can feel very different from gym to gym. Compare yourself to your own log on the same machine and seat setting.

Range of motion

How far to bend and straighten

Use the whole range, from as deep as the machine allows to fully straight. The bottom half of the rep, where the quads are longest, has the strongest growth evidence. In untrained women, reps from 100 to 65 degrees of knee bend grew the quads more than reps from 100 to 30 degrees, and top-half partials from 65 to 30 degrees grew about as much as not training in two of the measured regions (Pedrosa 2022).

Finish each rep at full lockout. On the leg extension the quads work hardest near full extension (Escamilla 1998), and the Larsen 2025 trial trained every rep from 110 degrees of knee bend to fully straight.

When full reps fail

Keep going with bottom-half partials. They keep the quads working in the part of the rep with the best growth evidence.

Myths

Leg extension myths

"Leg extensions are bad for your knees"Not for healthy knees. Even after ACL reconstruction, quad exercises like this one did not leave the knee looser than squat-style exercises across 10 trials (Perriman 2018). If the front of your knee hurts, go lighter or use less range.
"Stop short of lockout to keep tension"The top is the hardest part of this rep, not a rest. Quad activity peaks near full extension (Escamilla 1998), and the inner quad works hardest in the last part of the rep (Signorile 2014). Straighten fully, just do not slam into it.
"Toes out targets the teardrop"The one study that measured it found the opposite: turning the legs in drew the most inner and outer quad activity, and turning them out the most rectus femoris (Stoutenberg 2005). No study has shown a growth difference. Point your toes up and keep them there.
"Never lean back"Reclining against the backrest is the better setting (Larsen 2025). What to avoid is rocking your torso or lifting your hips to move the weight.
"Do them before squats to work the quads harder"A set of leg extensions before the leg press lowered quad activity and reps on the press (Augustsson 2003). Do them after your compound lifts.

Anatomy

Muscles worked

QuadricepsAll four straighten the knee. The rectus femoris also crosses the hip, and the leg extension grew it more than squats did (Zabaleta-Korta 2021). The three vastus muscles grow the same whatever the seat angle.

Primary

Core and gripKeep your hips on the seat while your hands hold the handles.

Stabilizer

Compare

Leg extension vs leg press vs squat

Attribute	Leg extension	Leg press	Squat
Rectus femoris	Works it most	Less	Less
Hardest point	Near lockout	Near the bottom	Near the bottom
Glutes	None	True	True
Best for	Quads alone, after compounds	Heavy quad volume	Strength and the whole leg

Verdict

Do both kinds. With the same training volume for 5 weeks, leg extensions grew all three regions of the rectus femoris while Smith machine squats grew only the middle of the vastus lateralis (Zabaleta-Korta 2021). The leg extension also drew more rectus femoris activity than the squat and leg press (Escamilla 1998).

Programming

Sets, reps and progression

3-4Sets

10-15Reps

0-2Reps left

The Larsen 2025 trial used 3 to 4 sets of 10 to 20 reps to failure, twice a week, and both legs grew. Stop most sets 0 to 2 reps short of failure, lift at a normal speed and lower over 2 seconds.

Stack plates are often 10 lb (5 kg) or more, a big jump on an isolation lift. Add reps first: when every set reaches the top of your range, move up one plate and drop back to the bottom of the range.

Form

Common mistakes

Knee off the pivotMove the backrest until the pivot dot lines up with the side of your knee. The pad should stay in one place on your shin.
Hips lifting off the seatThe weight is too heavy. Pull down on the handles and go lighter until your hips stay down.
Kicking the weight upMomentum carries the pad through the top of the rep. Lift under control and hold the top for a second.
Cutting the bottom shortLet your knees bend as far as the machine allows before the next rep. The bottom half grew the quads most (Pedrosa 2022).
Dropping the weightLower over 2 seconds and keep the plates off the stack between reps.

Variations

Leg extension variations

Single-leg extensionOne leg at a time on the same machine. Evens out a weaker side; the Larsen 2025 trial trained this way.

Paused leg extensionHold the top for 1 to 2 seconds every rep.

Slow eccentric leg extensionLower over 3 to 5 seconds. Harder with the same weight.

Reverse Nordic CurlKneel and lean back with your hips straight. Works the rectus femoris long, with no machine.

Sissy SquatKnees forward, heels up, body leaning back. A bodyweight quad isolation.

FAQ

Questions people ask

Are leg extensions bad for your knees?

Not for healthy knees. Even after ACL reconstruction, quad exercises like the leg extension did not leave the knee looser than squat-style exercises (Perriman 2018). If the front of your knee hurts, go lighter or use less range.

Should I lean back on the leg extension machine?

Yes, if the backrest reclines. Training with the hip bent 40 degrees instead of 90 grew the rectus femoris more, with the same growth in the other quads (Larsen 2025). Keep your back on the pad and your hips on the seat, and do not rock.

Should you point your toes in or out on leg extensions?

Neither matters much. Turning the legs in drew the most inner and outer quad activity and turning them out the most rectus femoris (Stoutenberg 2005), but no study has shown a difference in growth. Keep your toes pointed up.

Are leg extensions compound or isolation?

Isolation. Only the knee moves, so the quads do the work.

Leg extensions before or after squats?

After, for most goals. A set of leg extensions before the leg press lowered quad activity and reps on the press (Augustsson 2003). Do them first only on a day when the quads are the whole point.

What muscles does leg extension work?

The four quad muscles, the rectus femoris most of all. Nothing else moves, so the hamstrings and glutes do almost nothing.

How much weight should I leg extension?

For 10 reps, the median on Gravitus is 155 lb (70 kg) for men and 90 lb (40 kg) for women. The strongest quarter lifts 200 lb (90 kg) and 120 lb (52.5 kg) or more.

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