Single leg squats are one of the most effective lower body exercises you can do, but they’re also one of the hardest to learn. The movement requires you to lower your entire body weight on one leg while keeping your balance, which demands strength, stability, and coordination all at once. Here’s how to build up to them and perform them correctly.
The Basic Movement
Stand on one foot with your other leg lifted slightly off the ground. Keep your arms out in front of you for counterbalance, your core tight, and your torso relatively upright. Push your hips back and bend your standing knee to lower yourself as far as you can control. Pause briefly at the bottom, then drive through your foot to stand back up.
That’s the full version, sometimes called a pistol squat. For most people, getting there takes weeks or months of practice. The good news is that partial versions of the movement still build serious strength.
Where to Place Your Non-Working Leg
Where you hold the leg you’re not standing on actually changes which muscles work hardest. Research published in the Journal of Athletic Training found that holding your free leg in front of you or to the side activates your glutes significantly more during the lowering phase than holding it behind you. However, holding the leg in front also increases activity in the outer hip muscle that can pull your knee inward if your glutes aren’t strong enough to resist it.
For most people starting out, holding the free leg slightly in front of the body is the standard position. If you find your knee collapsing inward, try holding the leg to the side or slightly behind you while you build hip strength.
Start With Support
If you can’t do a full single leg squat yet, don’t force it. Begin by placing one hand on a sturdy surface like a countertop, table, or squat rack. This gives you a safety net for balance and lets you use your arm for a small assist at the bottom of the movement. Lift one foot behind you, bend through your standing knee, and lower yourself only as far as you can while maintaining control. Push back up through your foot.
Your first goal is simply to control the descent. Limit how deep you go and add depth over time as your strength improves. Even a quarter-depth single leg squat builds the stabilizing muscles in your hip and ankle that you’ll need for the full version.
Common Mistakes That Lead to Injury
The biggest form error in single leg squats is the knee caving inward, a pattern called dynamic knee valgus. This happens when the hip and glute muscles can’t control the femur’s rotation under load, and it shows up as the knee drifting toward the midline of your body instead of tracking over your toes. Repeated loading in this position increases stress on the ACL and the cartilage behind the kneecap, and over time it can contribute to knee pain and even early onset arthritis.
Poor alignment doesn’t just happen at the knee. It often starts at the trunk and pelvis. If your torso leans excessively to one side or your hips drop unevenly, the forces through your knee change. When you practice the movement, watch yourself in a mirror or record a video from the front. Your knee should stay roughly in line with your second toe throughout the entire squat. If it consistently drifts inward, you likely need more hip strengthening before adding depth or load.
Another common issue is the heel lifting off the ground, which shifts stress forward onto the knee. If your heel rises, try placing a small weight plate or wedge under it while you work on ankle mobility separately.
Why Single Leg Work Matters
Single leg squats build strength in the glutes, quadriceps, and hamstrings, but their real advantage is what they do for stability and balance. The gluteus medius, the muscle on the side of your hip responsible for keeping your pelvis level when you walk, run, or climb stairs, works hard during every rep.
There’s also a force production benefit. Unilateral squats with the same external load per leg produce greater peak ground reaction forces than bilateral squats, along with higher barbell velocity, which relates to power development. This phenomenon, called bilateral deficit, means your legs can collectively produce more force when they work independently than when they work together. For athletes, this translates to better sprinting, cutting, and jumping.
Single leg squats are also easier on the spine. Because you use much less external weight than a two-legged squat while achieving similar muscle activity in the hamstrings, calves, and core, they create substantially less spinal compression. This makes them a practical option if you have low back issues or are rehabbing a knee injury.
A Simple Progression Plan
Start with 3 sets of 8 to 10 repetitions per leg. Add 2 reps each week until you reach 12 to 14 per set, then progress to a harder variation rather than just piling on more reps. Here’s a logical order of difficulty:
- Supported single leg squat: One hand on a counter or rack, lowering to a comfortable depth. This is your starting point.
- Box single leg squat: Stand in front of a bench or chair and lower yourself until you lightly touch it, then stand back up. Lowering the box height over time increases the range of motion gradually.
- Eccentric-only single leg squat: Lower yourself on one leg as slowly as you can (aim for 3 to 5 seconds), then use both legs or your hands to help you back up. This builds strength in the hardest part of the movement without requiring you to stand back up on one leg yet.
- Full single leg squat: No support, full depth, free leg held in front. Once you own this, you can add load by holding a dumbbell or wearing a weight vest.
Two to three sessions per week is enough frequency to see steady progress. Give yourself at least one rest day between sessions so the muscles recover and adapt. Most people with a baseline of regular squatting or lunging can work up to the full version within 4 to 8 weeks using this progression. If you’re starting from scratch, give it longer and don’t rush past the supported variations.
Ankle Mobility and the Single Leg Squat
You’ll often hear that limited ankle flexibility is the main reason people fail single leg squats. The reality is more nuanced. A study in the International Journal of Sports Physical Therapy found no significant differences in ankle dorsiflexion range of motion between people who passed and failed a single leg squat test for knee control. People who failed had similar ankle mobility to those who passed.
This doesn’t mean ankle mobility is irrelevant. If your ankle is genuinely stiff, you’ll compensate by rounding your back or lifting your heel. But for most healthy people, the limiting factor is hip and core strength rather than ankle range of motion. If you suspect tight ankles are holding you back, test it: elevate your heels on a small wedge and try the squat again. If the movement instantly feels easier and your knee tracks better, ankle mobility work will help. If nothing changes, focus on hip strengthening instead.