# Sled Lying Single Leg Squat - Canonical: https://fitwill.app/exercise/10764/sled-lying-single-leg-squat/ - Media ID: 10764 - Primary muscle: Quads - Body part: Thighs - Equipment: Sled Machine - Video: https://fitwill.app/videos/10764/sled-lying-single-leg-squat.mp4 ## Description The Sled Lying Single Leg Squat is a unilateral pressing movement performed on a horizontal sled machine, often called a leg press or hip sled. You lie on your back on the machine's carriage with your head supported against the pad, place one foot flat on the resistance platform, and extend the hip and knee to drive the sled away before lowering it back under control. The non-working leg stays off the platform, usually resting on the floor or the machine frame, which is what makes this a true single-leg exercise rather than a standard two-legged press. Because each leg works on its own, this movement exposes and helps correct the strength differences between sides that a regular leg press can hide. The stronger leg can't take over, so the working quadriceps, glutes, and hamstrings have to do all of the work. The quadriceps are the primary drivers as the knee extends, while the glutes contribute heavily at the hip, and the calves and hamstrings assist with control and stability throughout the range. The lying position on the sled is a real advantage for people who struggle with balance during standing single-leg squats. Your back is fully supported, the sled tracks along a fixed path, and you can focus entirely on driving through the working leg without worrying about falling or compensating. That makes it a practical choice for rehabilitating one leg after injury, building strength in a lagging side, or loading a single leg heavily without placing compressive load through the spine the way a barbell split squat or standing squat would. Setup matters more than it might seem. The position of your foot on the platform changes which muscles dominate: placing it lower on the platform shifts more work to the quadriceps, while a higher placement brings the glutes and hamstrings more into the movement. Your hips and low back should stay pressed against the carriage, and your hands should grip the handles beside you to keep your torso stable as the sled moves. To perform it well, lower the sled until your knee travels toward your chest without your hips rolling off the pad or your lower back rounding, then press the sled back up by driving through the heel and mid-foot until the leg is nearly straight without snapping the knee into full lockout. The tempo should stay controlled in both directions, especially on the way down, since the eccentric portion is where much of the strength benefit lives. Common use cases include correcting left-to-right imbalances, adding volume to one leg after bilateral pressing, and progressing toward standing single-leg squat variations. As with any single-leg machine work, start with a lighter load than you think you need. One leg always feels harder than half of a two-legged press, and the last few inches of the descent are where form tends to break down. If your hips lift or your knee caves inward, reduce the weight and reset your position before continuing. ## Instructions 1. Sit onto the sled machine's carriage and lie back so your head and entire back are supported against the pad. 2. Place one foot flat on the resistance platform at about hip width from the center, and set your other foot on the floor or machine frame so it stays clear of the sled's path. 3. Grip the side handles firmly to anchor your torso, and check that your hips and lower back are pressed against the seat, not rolled off the edge. 4. Brace your core lightly and push the sled away to release the safety stops, then extend your working leg until the knee is almost straight. 5. Inhale and lower the sled under control, letting the knee bend and travel toward your torso while keeping the foot flat and the knee tracking in line with the toes. 6. Descend until the knee approaches the chest or as far as you can go without the hips lifting off the pad or the lower back rounding. 7. Exhale and press the sled back up by driving through the heel and mid-foot, extending the hip and knee together until just short of full lockout. 8. Keep the non-working leg relaxed and stationary so it does not assist or swing during the rep. 9. Complete all repetitions on one side, then re-set the sled safely and switch legs, matching the rep count and range on the second leg. ## Tips & Tricks - Foot placement decides the emphasis: slide the foot lower on the platform to bias the quads, or higher and slightly wider to shift work toward the glutes and hamstrings. - The most common mistake is pressing so deep that the tailbone tucks under and lifts off the pad — if you feel your hips rolling, shorten the range instead of forcing depth. - Do not lock the knee hard at the top; snapping into full extension under load shifts stress to the joint rather than the thigh muscles. - Watch for the knee caving inward as fatigue sets in — cue the knee to track over the little-toe side of the foot and slow the descent down. - Expect the first set on your weaker leg to feel uneven; always start with the weaker side and let it dictate the load and reps for the stronger side. - Gripping the handles hard helps, but pulling on them so your torso twists off the pad defeats the point — keep the shoulders square against the backrest. - Since there is no balance demand, use the stability to slow the lowering phase to two or three seconds; rushing the eccentric wastes the main benefit of the machine setup. - Keep the resting leg fully off the platform and out of the sled's travel path — a foot accidentally braced against the frame can turn a single-leg rep into an uneven two-leg press. - If the platform feels slippery or your foot slides under load, wear flat-soled shoes rather than going barefoot or in socks. ## Frequently Asked Questions ### Which muscles does the Sled Lying Single Leg Squat work? The quadriceps are the primary movers as the knee extends, with the glutes contributing at the hip. The hamstrings and calves assist with control, and the core works lightly to keep the torso stable on the pad. ### Is the Sled Lying Single Leg Squat suitable for beginners? Yes, and it is often easier to learn than standing single-leg squats because the sled tracks a fixed path and the back is fully supported. Start with a light load and a moderate depth until the hip position stays solid. ### How deep should I lower the sled on one leg? Lower until the knee travels close to your chest, but stop short of the point where your hips lift off the carriage or your lower back rounds. Depth that compromises hip position costs more than it gains. ### Why do one-leg reps feel so much harder than half my normal leg press weight? Single-leg work removes the ability to shift load between sides, and stabilizing on one foot changes how force is applied to the platform. Expect to use roughly 40 to 60 percent of your two-leg press load per leg at first. ### Can I use the Sled Lying Single Leg Squat to fix a strength imbalance between legs? That is one of its best uses. Start every set with the weaker leg, and only match — never exceed — the reps and weight that the weaker leg handles on the stronger side. ### Where should my non-working leg be during the exercise? Rest it flat on the floor beside the machine or on the frame, well clear of the sled's path. If it drifts up or braces against the platform, it will steal work from the leg you are training. ### What is a good substitute if my gym has no sled machine? A single-leg press on a standard leg press machine is the closest match, followed by Bulgarian split squats or rear-foot-elevated split squats with dumbbells, which train the same leg unilaterally with more balance demand. ### Should I fully straighten my leg at the top of each rep? Extend until the knee is nearly straight, then reverse direction without slamming into lockout. Hard lockouts under load place unnecessary stress on the knee joint while doing little extra for the muscles. ### Is it safe for my lower back? For most people, yes, because the back is supported and the load bypasses the spine. The main risk comes from going too deep and letting the pelvis tuck and lift off the pad, so keep the hips planted and the range honest.