What Muscles Does the Leg Press Work? (Complete Breakdown)

Ask what the leg press works and most people say "quads." A 12-week training study that measured 17 muscles with MRI gives a surprising answer: the leg press built the quads as expected, but the muscle that grew the most was the gluteus maximus, and the adductor magnus (inner thigh) grew too. Here's a muscle-by-muscle breakdown of the leg press, what the research says about each muscle, and how foot placement, backrest angle, and depth change the work.

Quick Answer

The leg press trains the quadriceps (the three vasti) and the gluteus maximus as prime movers, and it grows the adductor magnus too; those muscles grew most in a 12-week MRI study of untrained adults. The hamstrings grew a little, the calves steady the ankle, and the rectus femoris, the one quad muscle that crosses the hip, barely grew. Foot height may shift the work a little: one EMG study in 14 women found more quad and calf activity with a low placement and more glute activity with a high one at heavy loads, but another study found no difference, and neither measured growth. Stance width and toe angle barely change quad activation, and stopping at about 100° of knee bend grew the quads as well as going to each lifter's maximum, about 154°.

Leg Press Muscles Worked at a Glance

Primary Movers and the Adductor Magnus

These muscles push the platform away, and they're the ones that grew most when leg press training was measured with MRI.

1. Quadriceps (Front of the Thigh)

The quads are four muscles: the vastus lateralis (outer thigh), vastus medialis (the teardrop above the knee), vastus intermedius (beneath the rectus femoris), and rectus femoris (down the middle). The three vasti straighten the knee, which is the main job of the leg press.

They respond well. In a 12-week MRI study by Kinoshita and colleagues (Medicine & Science in Sports & Exercise, 2026), 17 untrained adults trained one leg on a single-leg press and the other on the leg extension, 5 sets of 10 reps at 70% of one-rep max (1RM), twice a week, with the knee bending to 90°. The leg press grew the vastus lateralis by 6.2%, the vastus medialis by 6.0%, and the vastus intermedius by 4.4%, with whole-quad growth of 4.9%, not significantly different from the leg extension (5.0–7.2% in the vasti, 7.1% for the whole quad). A 2020 systematic review by Martín-Fuentes and colleagues reports that in EMG studies the vastus lateralis and vastus medialis are the most active muscles in the leg press, followed by the rectus femoris, with quad activity peaking around 90° of knee bend.

The exception is the rectus femoris, the only quad muscle that crosses the hip as well as the knee. In Kinoshita's study it grew 1.1% on the leg press, which wasn't statistically significant, versus 13.2% on the leg extension. The authors' EMG data fit: at 50% of 1RM, the rectus femoris reached about 22% of maximum on the leg press, versus 35–37% for the vasti. Ema et al. (2016) offers a likely reason: rectus femoris activation during a leg press at 80% of 1RM was no higher than during a leg extension at 20% of 1RM, and it didn't rise in a set to exhaustion at 80% of 1RM, while the vasti's activation did. The authors traced the difference to hip extension: the rectus femoris also bends the hip, so it's used less when the hip is pushing the other way.

Loading bias: a lower foot placement may add a little quad activity (more below). To cover the rectus femoris, add leg extensions.

2. Gluteus Maximus

The glute max is the main hip extensor. In the leg press, the hips bend as the platform comes down and extend as you push it away, and the glutes drive that second half.

The leg press trains them harder than its reputation suggests. In Kinoshita's study, the gluteus maximus grew by 15.4%, the largest gain of the 17 muscles measured on the leg press, while the leg extension didn't grow it. The authors' follow-up EMG experiment showed the same pattern: at 50% of 1RM, the glutes reached about 41% of maximum on the leg press, versus about 9% on the leg extension. It's one study in untrained adults, so treat the exact number with care.

Loading bias: a higher foot placement may help. In Da Silva et al. (2008) (Journal of Strength and Conditioning Research), gluteus maximus activity was greater with a high foot placement than a low one at 80% of 1RM. Kinoshita's participants trained with their toes at the top edge of the footplate, which is a high placement.

3. Adductor Magnus (Inner Thigh)

The adductor magnus runs along the inside of the thigh. Its rear fibers extend the hip much like a hamstring does, so it helps on the push.

It's the leg press's least-known contributor. In Kinoshita's study, adductor magnus volume increased 6.2% with the leg press and didn't change with the leg extension. The smaller adductors (longus and brevis) didn't grow in either condition.

Loading bias: we found no leg press study that tested how to bias the adductor magnus. For direct work, the hip adduction machine trains the adductors without a platform.

Stabilizers and Secondary Movers

These muscles work on every rep, but where training studies measured them, they grew little or not at all.

4. Hamstrings (Back of the Thigh)

The hamstrings assist hip extension, but the leg press grows them only a little. In Kinoshita's study, hamstring volume rose by 3.1% over 12 weeks (5.3% in the long head of the biceps femoris), and the authors noted that this is far smaller than the 12–19% reported in studies that trained the hamstrings directly. The EMG data agree: in Escamilla et al. (1998) (Medicine & Science in Sports & Exercise), the squat produced about twice as much hamstring activity as the leg press.

Kinoshita's authors point to the same conflict as for the rectus femoris: the hamstrings cross both the hip and the knee, and their knee-bending pull works against the knee extension the press requires. They suggest the small growth came from co-activation, since the leg extension grew the hamstrings by a statistically similar amount.

What to do instead: train them directly with leg curls and Romanian deadlifts. See Best Hamstring Exercises Ranked.

5. Calves (Gastrocnemius and Soleus)

The calves steady the ankle and keep the platform balanced over the middle of your foot. In the Martín-Fuentes review, the medial gastrocnemius became more active as the knee approached full extension, and in Da Silva's study the gastrocnemius was more active with a low foot placement and in the 45-degree press than with a high placement. If you want bigger calves, press through your toes on the leg press calf raise; see Best Calf Exercises Ranked.

6. Glute Medius and Minimus

These smaller hip muscles keep your knees tracking over your toes instead of caving inward. They didn't grow significantly in Kinoshita's MRI study, so the leg press isn't a side-glute exercise.

7. Lower Back and Core

The seat takes over much of the job your spine does in a squat. Your abs and lower back still brace to keep your pelvis pressed into the pad, but much less than in a squat: in Saeterbakken et al. (2022), 19 trained women showed 17–59% lower core muscle activity in the leg press than in free-weight squats while lifting 47% more. That's why the leg press lets you load the legs hard when your lower back is the limiting factor. The one moment it matters is at the bottom of the rep: if the platform comes so close that your pelvis tucks under and your lower back rounds off the pad, the next push loads a rounded spine. Stop the descent where your hips stay flat.

How Foot Placement Changes the Work

Foot placement is the lever most lifters reach for, but the 2020 Martín-Fuentes review still calls it unclear whether foot height, stance width, or toe angle changes muscle activity, and it recommends a comfortable, self-selected stance until better evidence exists. Here's what the studies found:

• High vs low: in Da Silva's study of 14 women, a low foot placement produced more rectus femoris and vastus lateralis activity than a high placement at 80% of 1RM, while a high placement produced more gluteus maximus activity. Escamilla et al. (2001) found no significant difference in muscle activity between high and low placements at a lighter load, though a wide stance with a high placement produced more hamstring activity than a narrow stance with a high placement.
• Wide vs narrow: Martín-Fuentes et al. (2022) (Sports Health) compared stances of 100% and 150% of hip width, with the feet straight or turned out 45°, in trained men and women. Muscle activation didn't differ between stance widths or foot angles, though it rose when pressing as fast as possible; the vastus medialis was the most active of the four muscles measured in every condition. The same group's 2020 study in 10 trained women found the same for the quads, with a difference only in the gluteus medius between feet straight and turned out at maximal velocity. Escamilla's foot-angle comparison also found no differences.
• Knee forces: in Escamilla's 2001 study, the narrow stance produced greater compressive forces at the knee than the wide stance during the leg press, while the wide stance produced more tension in the posterior cruciate ligament (PCL). Knee forces didn't differ between the high and low placements.

Pick the stance that lets you keep your whole foot on the platform. If you want to experiment, move your feet up for the glutes or down for the quads, but treat that as a small, unproven tweak.

How Backrest Angle Changes the Work

Many 45-degree presses let you tilt the backrest. Marchetti et al. (2023) (Journal of Strength and Conditioning Research) tested two seat-to-backrest angles, 90° (more upright) and 125° (more reclined), in 15 trained men pressing 70% of their body mass. The reclined setting moved the hips through more range and produced more vastus lateralis activity, while the upright setting produced more biceps femoris (hamstring) activity. Gluteus maximus activity didn't differ. It's one small EMG study at a light load, so treat reclining the seat as a small tweak for the quads, not a rule.

How Depth Changes the Work

Deeper is not automatically better on the leg press. Larsen et al. (2025) (Journal of Sports Sciences) had 23 lifters with an average of 7 years of training do 4 sets of single-leg presses to failure twice a week for 8 weeks, one leg with the knee bending to about 100° and the other to the lifter's maximum, about 154°. Quad thickness grew similarly in both legs, though the study tested nothing shorter than 100°. EMG studies place peak quad activity around 90° of knee bend (Martín-Fuentes 2020), and the forces on the knee keep rising with depth: in Escamilla's studies, every knee force measured increased with knee flexion, and patellofemoral compressive force peaked at the deepest part of the rep.

The practical rule: bend your knees to at least 90°, and stop before your lower back rounds off the pad. Kinoshita's untrained adults stopped at 90° and Larsen's shorter-range legs at about 100°, and the quads grew in both. One limit: Larsen measured only the quads. Kinoshita's authors suggest that more hip flexion at the bottom, about 110°, could have grown the glutes and adductor magnus more, but neither study tested it.

45-Degree vs Horizontal vs Vertical Leg Press

Three machines share the name. The 45-degree (inclined) press is the one much of the EMG research above used: you recline, the platform sits above and in front of you, and the sled travels at about 45°. The horizontal (seated) press has you sit upright and push a platform straight ahead. The vertical press has you lie flat and push the platform straight up, so watch for your lower back rounding at the bottom. None of the studies in this guide measured it.

The same prime movers should do the work on all three, but we found no study that compared muscle growth across them. For how the 45-degree press compares with the hack squat and the vertical press, see Leg Press: 45° vs Hack vs Vertical.

Leg Press vs Squat

The leg press and the squat train the same prime movers, but the squat asks more of everything around them. In Escamilla's 2001 study of 10 experienced lifters, the squat produced more quad and hamstring activity than either leg press placement, and the 1998 study found about twice the hamstring activity. The squat also transfers better to jumping: in Wirth et al. (2016), 8 weeks of squats raised squat-jump and countermovement-jump height by about 12%, while the 3.5% and 0.5% changes after 8 weeks of 45-degree leg presses weren't statistically significant. Rossi et al. (2018) found squats built more squat strength, but jump and balance results didn't differ statistically between groups, and both exercises improved function.

What the leg press offers in return is load with far less lower-back demand. For the full comparison muscle by muscle, see What Muscles Do Squats Work.

How to Bias Each Muscle

For quads: the leg press already trains the vasti well. Two EMG findings may add a little, a low foot placement (Da Silva) and a reclined backrest (Marchetti), though neither was tested for growth. Bend your knees to at least 90°, and add leg extensions for the rectus femoris, which the leg press barely grows. See Best Quad Exercises Ranked.

For glutes: a high foot placement may help (Da Silva). In Kinoshita's study the glute max grew 15.4% with a hip-width stance, toes at the top edge of the footplate, and knees bending only to 90°, so a high placement at moderate depth was enough. The study didn't test a lower placement. See Best Glute Exercises Ranked.

For adductors: the single-leg press in Kinoshita's study grew the adductor magnus with a high, hip-width foot position. The hip adduction machine adds direct volume.

For hamstrings: the leg press won't do it (about 3% growth over 12 weeks). Use leg curls and Romanian deadlifts.

For calves: the leg press calf raise uses the same machine.

For sets, reps, and weekly volume, see the best rep range for hypertrophy and sets per week for muscle growth.

Common Mistakes That Change Which Muscles Work

• Lowering the platform until your lower back rounds: your pelvis tucks under and your spine takes load the seat was meant to spare it. Cue: stop where your hips stay flat on the pad. Stopping at about 100° of knee bend grew the quads as well as maximum depth (Larsen).
• Locking the knees out hard at the top: it takes tension off the quads. Cue: stop just short of straight.
• Feet so low your heels lift: you lose your base and your knees drift forward. Cue: whole foot on the platform.
• Expecting the leg press to build your hamstrings: it grew them about 3% in 12 weeks (Kinoshita). Add leg curls or Romanian deadlifts.
• Expecting it to replace squats for jumping: squats raised jump height far more in an 8-week study (Wirth).

The Bottom Line

The leg press builds the quads, glutes, and adductor magnus most, based on a 12-week MRI study of untrained adults, with the gluteus maximus growing the most of all. The hamstrings grow a little, the rectus femoris barely at all, and the seat takes most of the load off your lower back while it stays on the pad. Foot height is a small, unproven tweak (low may favor the quads, high the glutes), so start with the placement that feels best. Stance width and toe angle matter little for the quads, and reclining the backrest may add a little quad work. Stop the descent before your lower back rounds. Then fill the gaps: leg curls or Romanian deadlifts for the hamstrings, and leg extensions for the rectus femoris.

For more leg training, see Best Quad Exercises Ranked, Best Glute Exercises Ranked, and What Muscles Do Squats Work.