The single leg press primarily works your quadriceps, glutes, and hamstrings. With a standard, center-platform foot position, the workload splits roughly 40% quads, 30% glutes, and 30% hamstrings. But because you’re pressing with one leg at a time, smaller stabilizing muscles around the hip and core also have to work harder than they do during a regular two-legged press.
Primary Muscles Worked
Your quadriceps do the heaviest lifting during the single leg press. These four muscles on the front of your thigh are responsible for straightening the knee against resistance, and they dominate the pressing portion of the movement. The rectus femoris, which runs down the center of your thigh, shows the highest electrical activity of any muscle during the exercise, followed by the vastus lateralis and vastus medialis on the outer and inner sides of the knee.
Your glutes fire throughout the movement, particularly as you push the platform away from your body. They extend the hip, which is the straightening motion at your hip joint. Because only one leg is loaded, the gluteus medius on the side of your hip also has to engage to keep your pelvis from tilting or rotating. This is a stabilizing role it doesn’t need to play as aggressively during a bilateral press.
The hamstrings assist with hip extension alongside the glutes. Research comparing single-leg and bilateral lower body exercises found that the biceps femoris (the outer hamstring) shows significantly higher activation during single-leg variations than during standard bilateral movements. The effect size was large, suggesting this isn’t a trivial difference. If building your hamstrings is a priority, the single leg press has a slight edge over the two-legged version.
How Foot Placement Shifts the Work
Where you place your foot on the platform dramatically changes which muscles do the most work. This is one of the biggest practical advantages of the leg press: you can bias the exercise toward different muscle groups just by moving your foot a few inches.
- Low on the platform puts far more demand on your quads. With your foot in the bottom 25-30% of the platform, activation shifts to roughly 70% quads, 20% glutes, and 10% hamstrings. Your knee travels further forward and bends through a deeper range (110-120 degrees), which increases the work your quads have to do.
- High on the platform targets the glutes and hamstrings. Placing your foot in the upper portion flips the ratio to about 45% glutes, 35% hamstrings, and 20% quads. Your knee bends less (70-80 degrees), and the force shifts toward a more vertical push that lets your posterior chain take over.
- Center placement gives you the balanced 40/30/30 split across quads, glutes, and hamstrings. This is the standard starting point for most people.
Foot width matters too. A narrow stance (hip-width or less) emphasizes the outer quad sweep, with roughly 50% of the work going to the vastus lateralis. A wide stance at 1.5 to 2 times shoulder width shifts activation toward the inner thighs and adductors, with about 45% of the load going to those inner quad and adductor muscles.
Stabilizers and Core Engagement
When you press with one leg, your body has to resist rotation. The loaded side wants to pull your pelvis into a twist, and your core muscles, particularly the obliques and deep stabilizers along your spine, have to fire to keep everything square. This is work that barely registers during a two-legged press because the load is symmetrical.
The calf muscles also play a supporting role. The medial gastrocnemius (the inner head of your calf) shows moderate activation during single-leg pressing, helping to stabilize the ankle joint under load. The tibialis anterior on the front of your shin works to keep your foot in position on the platform.
Fixing Strength Imbalances
Most people have one leg that’s noticeably stronger than the other. During a bilateral leg press, your dominant leg quietly picks up the slack, and you never notice the gap. The single leg press eliminates this compensation entirely. Each leg has to move the weight on its own, which both reveals the imbalance and starts correcting it over time.
This matters for injury prevention. Strength asymmetries between your left and right sides can alter how you move during running, jumping, and cutting. By training each leg independently, you build more balanced hip strength, which supports better posture and more efficient movement patterns. This is why single-leg pressing is a staple in rehabilitation programs for athletes returning from lower body injuries.
Knee Joint Stress
One concern people have with the leg press is how it affects the knee, specifically the joint behind the kneecap (the patellofemoral joint). During pressing movements, stress on this joint increases as the knee bends deeper. At 90 degrees of knee flexion, patellofemoral stress during a weight-bearing press is significantly higher than at shallower angles. By 30 degrees or less, the stress drops substantially.
If you have knee pain, this has practical implications. Limiting your range of motion so the knee doesn’t bend past 60-70 degrees keeps patellofemoral stress relatively low. A high foot placement naturally reduces knee flexion, making it a better option for people working around knee sensitivity. Conversely, a low foot placement with deep knee bending maximizes quad activation but also maximizes joint stress, so it’s worth being deliberate about that tradeoff.
Protecting Your Lower Back
The most common form mistake on the single leg press is letting your pelvis tuck under at the bottom of the movement. This posterior pelvic tilt rounds your lower back away from the seat pad and places significant stress on your lumbar discs and ligaments. It can also irritate the sacroiliac joint where your spine meets your pelvis.
To avoid this, adjust the seat so your knee reaches at least a 90-degree angle when your back is flat against the support. Keep your back pressed firmly into the pad throughout the rep, engage your core before you start pressing, and drive through your heel rather than your toes. If you notice your hips rocking at the bottom of each rep, the range of motion is too deep for your current flexibility. Bring the sled stop up a notch and work within a range where your pelvis stays neutral.
Carryover to Athletic Performance
The single leg press builds strength that’s specific to how you actually use your legs. Running, jumping, and changing direction are all single-leg dominant activities. Training one leg at a time builds strength in a pattern that more closely mimics these movements than a bilateral press does.
That said, the direct carryover to power output is less clear-cut than you might expect. A study published in the International Journal of Strength and Conditioning found no significant difference in vertical jump improvement between groups that trained with unilateral versus bilateral leg press protocols. Strength gains were real in both groups, but they didn’t automatically translate into higher jumps. This suggests the single leg press is excellent for building foundational leg strength and correcting imbalances, but sport-specific power likely requires additional explosive training like plyometrics or Olympic lifts.