The leg press primarily targets your quadriceps, the four muscles running along the front of your thigh. Your glutes, hamstrings, and calves all contribute as secondary movers, but the quads do the heaviest lifting. What makes the leg press versatile is that small changes in foot position or machine type can shift emphasis between these muscle groups.
Primary Muscles: The Quadriceps
Your quadriceps are a group of four muscles that work together to extend your knee. All four heads activate during the leg press: the vastus lateralis on the outer thigh, the vastus medialis on the inner thigh near the kneecap, the vastus intermedius underneath, and the rectus femoris running down the center. These muscles fire hardest during the pushing phase, when you’re driving the sled away from your body. EMG studies show that quad activation increases meaningfully as you add load, with electrical activity in the rectus femoris jumping roughly 30% when intensity goes from 60% to 75% of a person’s max.
Because the leg press locks your body into a fixed path, your quads can generate more direct force than they would during a free-weight squat, where energy also goes toward balance and stabilization. This makes the leg press especially effective for isolating quad strength and size.
Secondary Muscles: Glutes, Hamstrings, and Calves
Your gluteus maximus activates throughout the movement, particularly at the bottom position when your hips are most flexed. However, the leg press doesn’t train your glutes through their full range. Compared with a squat, the 45-degree leg press skips the last 45 degrees of hip extension, meaning your glutes never reach full contraction. If glute development is a priority, the leg press alone won’t be enough.
Your hamstrings assist at the hip during the lowering and early pushing phases, though their contribution is modest. The three hamstring muscles (biceps femoris, semitendinosus, and semimembranosus) act more as stabilizers here than prime movers. Your calves, specifically the gastrocnemius and soleus, engage to stabilize the ankle joint against the foot plate but don’t receive a significant training stimulus.
How Foot Placement Changes the Target
Where you place your feet on the sled is the single biggest variable you can control. A low foot position, closer to the bottom of the platform, increases quadriceps activation because it forces greater knee flexion relative to hip flexion. A high foot position shifts more work to the glutes and hamstrings by increasing hip involvement.
Stance width also matters. A wide stance recruits the inner thigh muscles (adductors) and inner quads more heavily, with one analysis estimating roughly 45% of the work shifting to those muscles. A narrow stance does the opposite, emphasizing the vastus lateralis on the outer quad, which may account for about 50% of the muscle activation in that variation.
Interestingly, research published in Sports Health found that rotating your feet inward or outward on the platform did not meaningfully change overall muscle activation. So if you’ve been angling your toes to target specific muscles, it likely isn’t doing much. Stick to adjusting height and width instead.
Differences Between Machine Types
The type of leg press you use affects which muscles work hardest. The three most common variations each have a slightly different emphasis:
- 45-degree leg press: The standard plate-loaded sled found in most gyms. It engages all the major leg muscles with a strong quad bias. Your body sits at an angle and pushes the sled upward along a fixed track.
- Seated (horizontal) leg press: Your legs push straight out in front of you. This variation puts the most emphasis on the quadriceps because the hip angle stays relatively open throughout the movement, reducing glute and hamstring contribution.
- Vertical leg press: Your legs push straight up while you lie flat on your back. This version loads the posterior chain more heavily, meaning greater involvement from the hamstrings and glutes compared to the other two types.
If you only have access to one type, the 45-degree press is the most balanced option for overall lower body development.
Range of Motion and Muscle Growth
A common question is how deep you need to go on the leg press to maximize results. A 2025 study compared two groups of trained lifters: one working through about 100 degrees of knee flexion, the other using their full individual range (averaging around 154 degrees). After the training period, both groups saw similar quadriceps growth, with muscle thickness increases between 1 and 2 millimeters. Statistical analysis showed strong evidence that the deeper range offered no additional hypertrophy benefit.
This means you don’t need to bring your knees extremely close to your chest to build muscle. In fact, going excessively deep creates a separate risk. When the knees travel too far toward the chest, the pelvis tucks under (a “butt wink”), flattening the natural curve of your lower back. This increases pressure on the spinal discs and stresses the tissues most vulnerable to herniation. A controlled range where your knees reach roughly 90 degrees of flexion is effective for muscle growth and keeps your spine in a safer position.
How It Compares to Squats
The leg press and barbell squat train nearly the same lower body muscles, but they develop them differently. An eight-week study found that both exercises produced significant strength gains. However, the squat group also improved jump height, while the leg press group did not. The squat demands more from stabilizing muscles throughout the trunk, hips, and ankles, which translates better to athletic movement.
The leg press has its own advantage: because you’re locked into a fixed path, you can load the quads with more total force without worrying about balance or technique breakdown. This makes it a strong choice for building leg size, for training around a back injury, or for pushing volume after squats have already fatigued your stabilizers. One notable finding from biomechanics research is that no ACL forces were produced during the leg press in any variation tested, suggesting it can be a useful exercise during knee rehabilitation.
For most people, the leg press works best as a complement to squats rather than a replacement. It fills in the quad-dominant, high-load work that squats alone may not fully cover, while squats handle the functional strength and glute development that the leg press misses.