The Single-Leg Squat: What It Does, How to Do It, and Who It Is Worth It For

What the single-leg squat actually trains, the progression order, how many sets and reps to run, and who it is genuinely worth learning for.

The single-leg squat is one of the few exercises that tests strength, balance and ankle mobility at the same time. That is why plenty of people cannot do one even though they back squat 100 kg or more. It is not a party trick, it is a useful diagnostic and a solid training tool when you have no equipment.

What it actually does

The value is not that it looks hard. It is that it exposes and fixes things a two-legged squat hides.

Left-right imbalance. In a normal squat the stronger leg can take up to 15 percent more of the load and you will never feel it. On one leg the gap shows up immediately.
Hip stabilisers. The gluteus medius keeps the pelvis level. When it gives up, the knee drifts inward.
Ankle mobility. Without decent dorsiflexion there is no depth, full stop.
Less spinal load. No bar on the back, which makes it a usable option if heavy squats irritate your lower back.
Sport carryover. Running, football, basketball and hiking all happen on one leg, not two.

Two tests before you start

Wall ankle test. Put your big toe 10 cm from a wall and try to touch the wall with your knee without lifting the heel. If it does not reach, spend 4 to 6 weeks on ankle mobility first, 2 minutes per side, 5 days a week.
Bench lowering test. Use a bench 45 to 50 cm high, lower yourself on one leg over 3 seconds, 5 reps per leg. If you fall backwards or crash onto the bench, that is exactly where you start.

A five-level progression

Do not skip levels. Move up only when you hit the target reps cleanly on two sessions in a row.

Sit-downs to a 50 cm bench with a brief touch, 3 sets of 8 reps per leg.
Bench at 40 cm, then 30 cm, 3 sets of 8 reps.
Eccentric only: lower over 4 seconds to a 30 cm box, stand up with both legs, 3 sets of 5 reps.
Counterweight: hold 4 to 8 kg in front of your chest. It shifts your centre of mass forward and makes balancing far easier. 3 sets of 5 full-range reps.
Full unassisted squat, 3 to 4 sets of 3 to 5 reps.

A realistic timeline from zero to level five is 8 to 16 weeks training 2 to 3 times a week.

Technique, step by step

Stand on one leg, extend the other forward, knee nearly straight, foot 10 to 20 cm off the floor.
Reach both arms forward as a counterweight.
Keep your weight over the midfoot and heel. The heel stays down the whole time.
Lower under control for 3 seconds, knee tracking over the second and third toe.
Pause half a second at the bottom without relaxing, then stand up over 1 to 2 seconds.
Breathe in before you descend, breathe out once you clear the hardest point on the way up.

Your torso will lean forward and that is fine. A 30 to 45 degree lean is part of the movement, not a fault, as long as your back stays flat.

How much and how often

2 to 3 sessions a week, 3 to 4 sets of 5 to 8 reps per leg.
Rest 90 to 120 seconds between sets. This is a coordination lift and fatigue wrecks it.
Leave 2 to 3 reps in reserve. Training to failure here only degrades technique.
Always start with the weaker leg and give the stronger one the same number of reps, not more.
Progression: add 1 rep per week until you reach 8, then add 2 to 4 kg of counterweight and drop back to 5.

The usual mistakes

The heel lifts and the whole movement shifts onto the forefoot.
The knee collapses inward during the last 20 degrees of the descent.
Dropping into the bottom instead of lowering, which hammers the tendon below the kneecap.
The pelvis rotates, one hip swings back, and the load migrates into the lower back.
Training only to a comfortable depth for months without ever increasing range.

Who it is worth it for

It is worth it if you run, play a sport with direction changes, hike, train at home without weights, or are coming back from a one-sided injury and need to even the legs out.

It is not worth forcing if your goal is a maximal barbell squat, since Bulgarian split squats with 20 to 40 kg deliver more for that goal. The same applies if you carry significantly more bodyweight, if deep knee flexion is painful for you, or if the ankle mobility simply is not there. In those cases split squats and Bulgarian split squats give you roughly 80 percent of the benefit without demanding extreme depth.

When to see a doctor

Do not self-diagnose, and do not train through any of these:

Knee pain above 4 on a 10-point scale, or any pain lasting longer than 2 weeks.
Knee swelling within 24 hours of a session.
A sense that the knee is giving way or locking, with painful clicking.
Pain at night or at rest.
Previous ligament or meniscus surgery. Ask the physiotherapist who handled your rehab before you start.

The short version

The single-leg squat exposes leg imbalances, builds hip stabilisers, and demands decent ankle mobility.
Work the five levels: 50 cm bench, 30 cm bench, eccentrics, 4 to 8 kg counterweight, then the full movement.
The dose is 2 to 3 sessions a week, 3 to 4 sets of 5 to 8 reps, resting 90 to 120 seconds.
Always start with the weaker leg and match, not exceed, that rep count on the stronger side.
Pain above 4 out of 10, swelling, or a knee that gives way means stop and get it checked, not one more set.