The single leg squat is one of the most valuable and most demanding lower body exercises available. It develops unilateral quadriceps, glute, and posterior chain strength, reveals and addresses side-to-side strength asymmetries that bilateral squats conceal, and develops the single-leg stability and pelvic control that transfer directly to running, jumping, and athletic cutting movements.
Despite its value, the single leg squat is frequently attempted before the prerequisite strength and control exist, producing the knee valgus, pelvic drop, and trunk compensation patterns that indicate the exercise is beyond the current level. The key to single leg squat development is understanding the progression from the most accessible assisted versions to the most demanding unassisted and loaded versions, and advancing through this progression based on quality rather than speed.
What Single Leg Squats Are
A single leg squat is any squat pattern performed on one leg, where only one foot is in contact with the ground throughout the movement. The non-working leg is held in the air.
The spectrum of single leg squat variations:
At the accessible end: the single leg squat to a high box, where the athlete sits back onto a box and stands on one leg. This version requires minimal flexibility and moderate strength.
At the demanding end: the full pistol squat, where the athlete descends to the floor with the non-working leg extended straight in front and the working leg completely compressed to the bottom of its range. This version requires excellent ankle dorsiflexion, hip flexor strength, and single-leg quad strength.
Between these extremes sits the majority of single leg squat training, where depth, box height, and assistance level are progressively modified to match the athlete’s current capacity.
Single Leg Squat Versus Pistol Squat
These terms are often used interchangeably but are more precisely defined as different points on the same progression:
Single leg squat: Any single-leg squatting movement, typically to approximately parallel depth (thigh horizontal). The non-working leg may be held to the side or bent behind the body. This is the term used in most rehabilitation and athletic training contexts.
Pistol squat: The extreme end-range version where the athlete descends to the lowest possible position with the non-working leg extended straight in front and horizontal. This requires extreme ankle dorsiflexion, hip flexor strength, and single-leg quad strength that most people do not have without specific training.
This guide covers the full single leg squat spectrum with the pistol squat as the advanced end-point progression rather than the default target.
Why Single Leg Squats Are Valuable
Unilateral strength development: Bilateral squats allow the stronger leg to compensate for the weaker. Single leg squats prevent this compensation and develop each leg independently, addressing the side-to-side asymmetries that are common in athletes and that are associated with injury risk.
Functional specificity: Walking, running, stair climbing, and virtually every athletic movement involves single-leg loading phases. Single leg squat strength transfers more directly to these activities than bilateral squat strength.
Pelvic and hip stability: The single-leg loading requires the gluteus medius to work harder than during bilateral squats, developing the pelvic control that is a primary determinant of knee health and running mechanics.
Asymmetry assessment: The single leg squat test (covered in the single leg squat test article on this site) is a primary movement screening tool in sports medicine. The ability to perform a controlled single leg squat without knee valgus or hip drop is one of the most informative single assessments of lower extremity movement quality.
Reduced spinal loading: At equivalent training stimuli, single leg squats require less total load than bilateral squats, producing a similar muscle stimulus with less spinal compression. This is relevant for athletes who need to manage spinal loading during high-volume training phases.
Prerequisites
Before attempting unassisted single leg squats, the following strength and mobility foundations should be established:
Single-leg balance: Ability to balance on one leg for 30 seconds without stepping. As covered in the balance drills for athletes article on this site, single-leg balance is the prerequisite for all single-leg loading.
Bilateral squat depth: The ability to perform a bilateral squat to at least parallel with correct knee tracking (no valgus, no heel rise) before unilateral loading is introduced.
Hip abductor strength: Adequate gluteus medius strength to prevent significant pelvic drop during single-leg stance. As covered in the what is knee valgus article on this site, the lateral band walk and clamshell should be well-established before single leg squat training begins.
Ankle dorsiflexion: Sufficient ankle dorsiflexion to allow the knee to travel over the toes during the descent without heel rise. Limited ankle dorsiflexion is one of the most common limitations in single leg squat performance.
Step-by-Step Technique
Standard Single Leg Squat to Box
The most appropriate starting technique for most people beginning single leg squat training.
Setup:
- Stand facing forward on one leg, with a box or bench of appropriate height behind you
- The non-working leg is held out in front (knee slightly bent) or to the side
- Arms extended forward for counterbalance
The descent:
- Push the hips backward and downward, initiating the movement from the hip rather than the knee
- Allow the torso to lean forward slightly as the hips push back
- The standing knee tracks over the second and third toe throughout the descent
- Lower until the hips lightly touch the box
- Do not sit fully onto the box: the touch is a depth marker, not a rest
The return:
- Drive through the standing heel to return to the standing position
- The knee continues to track over the toes during the return
- Extend fully at the top before the next rep
Box height selection: Begin with a box height that allows the movement to be completed with correct knee tracking and level pelvis. For most beginners to single leg squats, this may be a high box (45 to 50 centimetres). Progressively reduce the box height as strength and control develop.
Freestanding Single Leg Squat (No Box)
Once the box version at approximately parallel depth is achievable, progress to the freestanding version.
Technique differences from the box version:
- No box provides a depth reference: depth is controlled entirely by strength and control
- The descent is self-regulated, stopping at the point where correct alignment can be maintained
- The return requires full concentric strength without the box’s assistance with the transition from eccentric to concentric
Non-working leg position:
The non-working leg can be held in two positions:
Held to the side (easier): The non-working leg extends to the side, providing some counterbalance. Less demanding on hip flexor strength.
Held in front (harder): The non-working leg extends forward and horizontal, as in the pistol squat progression. This requires significant hip flexor strength and challenges balance more substantially.
Key Technique Cues
Hip push-back initiates the movement: The most important single cue. The descent should begin by pushing the hips backward (as in the hip hinge), not by bending the knee forward. This hip-first initiation engages the posterior chain and prevents the forward knee travel that overloads the patellofemoral joint and makes the movement quad-dominant.
Knee over the middle toes throughout: The standing knee must track over the second and third toe at every point during the descent and return. Any inward drift (knee valgus) indicates insufficient gluteus medius or hip external rotator strength and must be corrected immediately.
Heel flat throughout: The standing heel must remain in contact with the floor throughout the entire movement. Heel rise indicates insufficient ankle dorsiflexion and can be addressed with a heel elevation initially, while ankle mobility is developed separately.
Level hips: The non-working hip should remain approximately level with the working hip. Any significant drop on the non-working side indicates gluteus medius insufficiency.
Controlled tempo: Each descent should take 2 to 3 seconds. Rapid dropping uses momentum to assist the movement, bypassing the eccentric strength development that is one of the primary training benefits.
Common Errors and Fixes
Error 1: Knee Valgus During Descent or Return
What it looks like: The standing knee drifts inward, medial to the line of the second and third toe, during any part of the movement.
Why it happens: Insufficient gluteus medius and hip external rotator strength to maintain femoral position under the single-leg loading demand.
Fix: Reduce the depth to the range where the knee can track correctly. Strengthen the hip abductors with clamshells, lateral band walks, and single-leg glute bridges before attempting deeper single leg squats. As covered in the what is knee valgus article on this site, the lateral step down is a specific exercise for developing the eccentric hip control needed for correct single leg squat mechanics.
Error 2: Excessive Trunk Forward Lean
What it looks like: The torso leans significantly forward during the descent, with the chest approaching the knee.
Why it happens: Insufficient quadriceps strength or ankle dorsiflexion, causing the body to shift its centre of mass forward to assist the movement.
Fix: Check the ankle dorsiflexion first: heel rise accompanying the forward lean indicates ankle restriction that should be addressed separately. If ankle dorsiflexion is adequate, the forward lean indicates quad weakness. Use a higher box target initially and build toward greater depth as quad strength develops.
Error 3: Pelvic Drop on the Non-Working Side
What it looks like: The hip on the non-working side drops visibly below the working hip during the descent.
Why it happens: Gluteus medius weakness on the working side.
Fix: Reduce the depth to where pelvic level can be maintained. Increase the gluteus medius work (lateral band walk, clamshell, step-down) before returning to the single leg squat.
Error 4: Heel Rising
What it looks like: The standing heel lifts off the floor during the descent, particularly in the lower ranges.
Why it happens: Insufficient ankle dorsiflexion.
Fix: Place a 1 to 2 centimetre heel elevation (a weight plate under the heel) while ankle mobility is developed through specific ankle dorsiflexion work. Progressively reduce the heel elevation as flexibility improves.
Error 5: Sitting Back Too Far (Not Squatting)
What it looks like: The movement is a single-leg hinge backward rather than a squat, with minimal knee flexion and excessive hip hinge.
Why it happens: The person is using a hip-hinge pattern (more natural for most people) rather than the squat pattern (hip and knee flexion simultaneously).
Fix: Cue the knee to travel forward over the toes while the hips push back simultaneously. The single leg squat involves both knee flexion and hip flexion, not just one or the other.
Progressions
Level 1: Assisted Single Leg Squat (TRX or Pole)
Hold a TRX strap, pole, or stable support lightly with both hands. The support allows greater depth to be reached while developing the movement pattern before full unassisted strength is available.
How to do it:
- Hold the support lightly (fingertips only, not gripping for dear life)
- Perform the single leg squat to as deep a range as the technique allows
- Use the support only as much as necessary to maintain correct alignment
- Progressively reduce the support over weeks as strength develops
Sets and reps: 3 sets of 8 to 10 per side
Level 2: Single Leg Squat to High Box
Standard box version as described in the technique section. Box at 45 to 50 centimetres.
Sets and reps: 3 sets of 8 per side
Level 3: Single Leg Squat to Medium Box
Reduce the box height to 35 to 40 centimetres. Greater range of motion and greater quad demand.
Sets and reps: 3 sets of 8 per side
Level 4: Single Leg Squat to Low Box (Near Parallel)
Box at approximately 25 to 30 centimetres, placing the thigh near parallel at the bottom.
Sets and reps: 3 sets of 8 per side
Level 5: Freestanding Single Leg Squat to Parallel
No box. Descend to approximately parallel under complete muscular control.
Sets and reps: 3 sets of 8 per side
Level 6: Single Leg Squat With Counterbalance Weight
Holding a light weight (5 to 10 kilograms) at chest height shifts the centre of mass and counterintuitively makes the deep single leg squat more accessible by providing a forward counterbalance. This is a useful bridge between freestanding parallel and full depth.
Sets and reps: 3 sets of 8 per side
Level 7: Loaded Single Leg Squat
Hold dumbbells at the sides or a kettlebell in the goblet position to add external resistance.
Sets and reps: 3 sets of 6 to 8 per side at progressive loading
Level 8: Pistol Squat
The full pistol squat: descent to the lowest position with the non-working leg extended horizontally in front.
Additional requirements beyond the standard single leg squat:
- Significant hip flexor strength (to hold the non-working leg extended)
- Full ankle dorsiflexion (to allow the heel to remain flat at the bottom)
- Full hip flexion range on the working side
- Core and hip flexor endurance to maintain the non-working leg position throughout
Progressive approach to the pistol squat:
Begin with an assisted pistol (holding a support) to a box, gradually reducing the box height while developing the specific mobility and strength required. A common intermediate step is the pistol squat with the non-working leg allowed to rest on a band stretched between two poles at shin height.
Sets and reps: 3 sets of 3 to 5 per side when first learning, progressing to 5 to 8 reps as proficiency develops
Sport-Specific Applications
For runners: The single leg squat develops the unilateral quad and glute strength alongside the pelvic control that is directly relevant to the stance phase of running. Athletes who can maintain correct single leg squat mechanics typically show better running economy and fewer overuse injuries than those with poor single-leg squat control.
For basketball and volleyball athletes: The ability to land and rebound from a single-leg position under control is the most injury-relevant movement for these athletes. The single leg squat to a box develops the eccentric quad control most specific to single-leg landing mechanics.
For football and soccer players: The cutting and direction change mechanics of field sports require single-leg loading capacity in multiple planes. Single leg squat strength is a primary predictor of performance in these movements.
For ACL injury prevention: As covered in the what is knee valgus article on this site, the ability to perform a single leg squat without knee valgus is one of the primary criteria for ACL injury prevention screening and return-to-sport clearance following ACL reconstruction.
Programming Single Leg Squats
For athletic development:
3 sets of 8 per side at the appropriate progression level, 2 to 3 times per week. Progress the box height or depth only when 3 sets of 8 can be completed with perfect technique (no valgus, no hip drop, no trunk lean).
For rehabilitation:
Single leg squats are typically introduced in the intermediate phase of knee rehabilitation (weeks 4 to 8 of most protocols, depending on the condition). Begin with the high box version and progress depth based on pain response (below 3 to 4 out of 10) and technique quality.
Combined with bilateral squats:
Both bilateral and unilateral squats belong in a complete programme. Bilateral squats allow heavier absolute loading; single leg squats address asymmetry and functional specificity. A practical split:
Day 1: Barbell squat (primary bilateral) + single leg squat to box (accessory unilateral)
Day 2: Single leg squat freestanding (primary unilateral) + goblet squat (accessory bilateral)
Asymmetry correction:
When one side is significantly weaker (unable to achieve the same depth or requiring significantly more trunk compensation), give the weaker side one additional set per session until the asymmetry reduces to within 10 percent.
Frequently Asked Questions
Is the single leg squat the same as a lunge?
No. A lunge involves a stepping or split-stance pattern where both feet make contact with the ground at some point during the movement. The single leg squat is performed entirely on one leg, with the other leg held off the ground. The single leg squat is generally more demanding for balance and pelvic stability than the lunge, and more specifically develops the qualities assessed in sports medicine screening.
How deep should a single leg squat go?
Depth should be determined by the athlete’s ability to maintain correct technique (no knee valgus, no heel rise, no hip drop, no trunk lean) throughout the movement. For most athletic applications, achieving parallel depth (thigh horizontal) with correct technique is the appropriate target. Deeper than parallel is appropriate only when the specific mobility and strength for that depth exist.
Can single leg squats hurt knees?
Performed with correct technique, single leg squats are a safe and beneficial exercise for healthy knees. Knee pain during single leg squats typically indicates either incorrect technique (knee valgus being the most common) or an underlying knee condition that requires assessment. The most important correction for knee pain during single leg squats is ensuring the knee tracks over the second and third toe throughout the movement.
How long does it take to develop a full single leg squat from scratch?
This depends heavily on the starting level. Someone with good bilateral squat mechanics and adequate hip strength may achieve a solid single leg squat to parallel within 4 to 6 weeks of targeted training. Someone starting with significant asymmetry, poor hip control, or limited ankle mobility may take 3 to 6 months to achieve the same. The progression should be based on quality at each level rather than a fixed timeline.
Should I include single leg squats if I can already barbell squat twice my bodyweight?
Yes. Bilateral strength and unilateral strength are related but not identical. Many strong bilateral squatters discover significant asymmetry and poor pelvic control when first attempting single leg squats. The functional specificity of the single-leg pattern and the asymmetry correction it provides make it valuable regardless of bilateral strength level.