Most strength training programmes are built around bilateral exercises: back squats, deadlifts, bench presses, and barbell rows. These are effective exercises that develop general strength and muscle mass. But they share a fundamental limitation for athletes in most sports: almost no athletic action of consequence is bilateral.
Running, sprinting, kicking, jumping from an approach, changing direction, throwing, and striking are all performed primarily with one limb at a time. An athlete who builds all of their strength through bilateral exercises develops the capacity to produce force with both limbs together but not the specific unilateral strength, balance, and coordination that sport actually demands.
Unilateral training, exercises performed one limb at a time or with significantly asymmetric loading, directly addresses this gap. It develops the qualities that bilateral training misses: single-limb strength, balance and proprioception under load, the ability to identify and correct side-to-side strength asymmetries, and the sport-specific coordination of movements performed on one leg or one arm at a time.
The Bilateral Deficit: Why One Plus One Does Not Equal Two
The bilateral deficit is one of the most important concepts in strength and conditioning and one of the least understood outside specialist circles.
Research has consistently found that the force produced by two limbs working together in a bilateral exercise is less than the sum of the forces each limb can produce independently in a unilateral exercise. In practical terms, this means that an athlete who can leg press 100 kilograms with each leg individually (200 kilograms total) typically cannot leg press 200 kilograms with both legs together. The bilateral press is usually 85 to 95 percent of the sum of the unilateral presses.
Why the bilateral deficit occurs:
The bilateral deficit is a neural phenomenon. When both limbs work simultaneously, the nervous system reduces the neural drive to each limb compared to when each limb works alone. The precise mechanism is debated but is related to the interhemispheric inhibition between the two brain hemispheres during bilateral contractions.
Why it matters for training:
The bilateral deficit means that bilateral exercises are performed at a lower percentage of each limb’s maximum capacity than unilateral exercises. Unilateral exercises force each limb to produce force at or near its actual maximum, providing a more complete strength stimulus than bilateral exercises at the same absolute load.
The bilateral deficit reversal:
Interestingly, some highly trained athletes actually show a bilateral facilitation rather than a bilateral deficit, where bilateral force production exceeds the sum of unilateral forces. This facilitation is associated with extensive bilateral training (powerlifters, weightlifters) and suggests that the neural adaptations of unilateral training and bilateral training are distinct and complementary.
Identifying and Addressing Asymmetries
Side-to-side strength and movement asymmetries are one of the most reliable predictors of injury risk in athletes. Research has consistently found that asymmetries of more than 10 to 15 percent between limbs in strength and power tests are associated with higher rates of muscle strains, ligament injuries, and overuse problems.
How to assess your asymmetry:
Single-leg squat assessment:
Stand on one leg and lower into a single-leg squat as far as comfortable. Observe:
- Does the knee track over the toes or does it collapse inward?
- Can you maintain a level pelvis throughout the movement?
- How much range is available on each side?
- Is there a noticeable difference in strength or control between sides?
Single-leg hop for distance:
As covered in the one-leg jumping article on this site, hop for maximum distance on each leg and compare. A difference of more than 10 percent between legs indicates a meaningful asymmetry.
Bulgarian split squat comparison:
Perform 5 Bulgarian split squats at a moderate load on each leg and note any difference in the effort required or the control available between sides.
Addressing asymmetries in training:
When asymmetries are identified, give the weaker side an additional set of every unilateral exercise throughout the training programme. For example, if the right leg is weaker, perform 3 sets on the right and 2 on the left for all lower body unilateral exercises. Maintain this asymmetric volume until the difference between sides reduces to less than 10 percent.
The Best Unilateral Exercises by Movement Pattern
Lower Body: Squat Pattern
Bulgarian Split Squat
Why it is the most important unilateral lower body exercise: The Bulgarian split squat develops single-leg quad, glute, and hip stability in the specific loading pattern of the athletic push-off. It allows heavier loading than most other single-leg exercises while maintaining the unilateral stimulus.
How to do it:
- Stand facing away from a bench with one foot elevated on the bench behind you
- The front foot should be far enough forward that the shin is approximately vertical when the knee is bent
- Lower the body by bending the front knee until the rear knee approaches the floor
- Drive through the front heel to return to standing
- Complete 3 to 4 sets of 8 reps per leg
Key cue: The front knee must track over the second and third toes throughout. Knee cave during a Bulgarian split squat reflects the same hip stability weakness that causes knee cave during sprinting and landing.
Progression:
- Bodyweight: master the mechanics
- Dumbbell held at sides: moderate loading
- Barbell on shoulders: heavy loading
- Rear foot elevated on a higher surface: increased range of motion demand
Single-Leg Squat (Pistol Squat)
Why it matters: The most demanding unilateral squat variation, requiring the highest levels of single-leg strength, balance, and ankle mobility simultaneously.
How to do it:
- Stand on one leg with the other leg extended forward
- Lower into a full squat on the standing leg while keeping the extended leg off the floor
- Maintain an upright trunk throughout
- Drive through the heel to stand
- Complete 3 sets of 5 reps per leg when achievable
Progression from assisted to unassisted:
- Assisted pistol holding a suspension trainer or rack upright for balance support
- Box pistol squat: squat to a box of progressively decreasing height
- Full pistol squat
Step-Up
Why it matters: A functional unilateral squat pattern that directly replicates stair climbing and the step-up action of sprint acceleration.
How to do it:
- Stand facing a box of 40 to 50 centimetres
- Place one foot fully on the box
- Drive through the working foot to step up, bringing the other foot to the box
- Step back down and repeat
- Complete 3 sets of 10 reps per leg
Lateral Step-Up:
Step up sideways onto the box, developing the lateral hip strength relevant to direction changes.
Lower Body: Hinge Pattern
Single-Leg Romanian Deadlift
Why it is essential: Every running stride involves a single-leg hip extension supported by the posterior chain. The single-leg Romanian deadlift develops this exact quality while also developing the balance and proprioception of single-leg athletic movements.
How to do it:
- Stand on one leg with a slight bend in the knee
- Hold a dumbbell in the hand opposite to the standing leg
- Push the hips backward and allow the torso to lean forward as the free leg extends behind
- Lower until a strong hamstring stretch is felt in the standing leg
- Drive the hips forward to return to standing
- Complete 3 sets of 8 reps per leg
Key cue: The hips should remain level throughout. If one hip drops significantly, the gluteus medius of the standing leg is weak. Address this with clamshells and lateral band walks before adding significant load to this exercise.
Single-Leg Hip Thrust
Why it matters: Develops the glute strength of the single-leg hip extension pattern in a position that maximises gluteus maximus activation.
How to do it:
- Sit with the upper back against a bench, one foot on the floor and one leg extended
- Drive the hips upward on the single standing leg
- Squeeze the glute firmly at the top
- Hold for 1 second and lower
- Complete 3 sets of 10 reps per leg
Upper Body: Push Pattern
Single-Arm Dumbbell Press
Why it matters: Develops unilateral horizontal pressing strength and anti-rotation core stability simultaneously.
How to do it:
- Lie on a bench holding a dumbbell in one hand, the other arm resting
- Press the dumbbell toward the ceiling
- The asymmetric loading requires significant core anti-rotation effort
- Lower slowly and repeat
- Complete 3 sets of 10 reps per side
Single-Arm Push-Up
Why it matters: The most demanding unilateral pushing exercise, developing explosive single-arm pushing power and anti-rotation stability.
How to do it:
- Start in a wide-stance push-up position
- Place one hand behind the back
- Lower the body toward the floor on the single arm
- Push back to the starting position
- Complete 3 sets of 5 reps per side when achievable
Progression:
- Inclined single-arm push-up (hands on a bench): reduces the load
- Floor single-arm push-up: full load
- Plyo single-arm push-up: explosive version
Cable or Band Single-Arm Press
Why it matters: Develops unilateral pressing strength in a standing position with a rotational component that is more sport-specific than the bench-based version.
How to do it:
- Anchor a cable or band at chest height to one side
- Stand with the anchor to the side, holding the handle in one hand
- Press the handle forward against the resistance
- The rotational pull of the single-arm cable press requires significant anti-rotation core effort
- Complete 3 sets of 12 reps per side
Upper Body: Pull Pattern
Single-Arm Dumbbell Row
Why it matters: Develops unilateral pulling strength and anti-rotation core stability in a functional position.
How to do it:
- Place one hand and knee on a bench for support
- Hold a dumbbell in the other hand with the arm extended
- Pull the dumbbell toward the lower rib, leading with the elbow
- Lower slowly
- Complete 3 sets of 10 reps per side
Single-Arm Pull-Up or Cable Pull-Down
Why it matters: Develops unilateral vertical pulling strength and the asymmetric loading demands that bilateral pull-ups cannot provide.
How to do it (single-arm cable pull-down):
- Set a cable at high pulley with a single handle
- Hold the handle with one hand, arm extended overhead
- Pull the handle toward the shoulder
- Control the return
- Complete 3 sets of 10 per side
Carries
Loaded carry exercises are among the most effective unilateral training tools because they challenge the entire body to maintain position under asymmetric loading for sustained periods.
Single-Arm Farmer’s Carry
Why it matters: The asymmetric load of holding a heavy implement in one hand forces the core to resist lateral flexion (side bend) while the hip abductors resist pelvic drop. This directly trains the anti-lateral flexion stability that protects the lower back and supports athletic movement.
How to do it:
- Hold a heavy dumbbell or kettlebell in one hand
- Walk for 20 to 30 metres at a controlled pace
- Keep the trunk upright without leaning toward the loaded side
- The shoulder on the loaded side should not drop significantly below the unloaded side
- Complete 3 to 4 carries per side
Key cue: The challenge is to appear from a distance as if you are walking with no weight at all. Any visible trunk lean or shoulder drop indicates the weight is beyond the current anti-lateral flexion capacity and should be reduced.
Waiter’s Walk
Why it matters: Develops shoulder stability and overhead unilateral strength under a sustained carry.
How to do it:
- Hold a dumbbell or kettlebell overhead in one hand with the arm locked out
- Walk for 20 to 30 metres at a controlled pace
- Keep the shoulder packed and the arm vertical throughout
- Complete 3 to 4 carries per side
Suitcase Carry:
Similar to the farmer’s carry but with the weight held lower, emphasising anti-lateral flexion at a different leverage point.
How to Programme Unilateral Training
The bilateral to unilateral ratio:
For most athletes in most sports, a training programme that includes approximately 60 percent unilateral exercises and 40 percent bilateral exercises produces the best balance of sport-specific strength development and maximum strength development.
For powerlifters and Olympic weightlifters, where the sport itself is bilateral, a higher proportion of bilateral work is appropriate. For sprinters, basketball players, and field sport athletes, a higher proportion of unilateral work is warranted.
Integrating unilateral work into a training week:
Option 1: Unilateral emphasis days
Designate specific training days for unilateral lower body and upper body work. This allows full development of each movement pattern without the fatigue from bilateral exercises limiting the quality of unilateral work.
Monday: Bilateral lower body (squat, deadlift)
Tuesday: Unilateral upper body (single-arm press, single-arm row, carries)
Thursday: Unilateral lower body (Bulgarian split squat, single-leg RDL, step-up)
Friday: Bilateral upper body (bench press, barbell row)
Option 2: Mixed sessions
Include one bilateral and one unilateral exercise for each movement pattern in every session.
Lower body session:
- Back squat: 4 x 5 (bilateral)
- Bulgarian split squat: 3 x 8 per leg (unilateral)
- Romanian deadlift: 3 x 8 (bilateral)
- Single-leg RDL: 3 x 8 per leg (unilateral)
Upper body session:
- Bench press: 4 x 5 (bilateral)
- Single-arm dumbbell press: 3 x 10 per side (unilateral)
- Barbell row: 3 x 8 (bilateral)
- Single-arm row: 3 x 10 per side (unilateral)
Volume considerations:
Unilateral exercises typically require lower absolute loads than bilateral exercises but the per-limb demand is higher. Begin with conservative loads and build progressively. The Bulgarian split squat in particular produces more delayed onset muscle soreness than most athletes expect in the first 2 to 3 weeks of introduction.
Sport-Specific Unilateral Applications
Running and endurance sports:
Single-leg RDL, Bulgarian split squat, and single-leg hip thrust develop the posterior chain strength of each running stride. Single-arm farmer’s carry develops the core anti-rotation stability that maintains efficient running posture under fatigue.
Basketball and volleyball:
Single-leg box jump, Bulgarian split squat, and single-leg depth jump develop the unilateral explosive power of approach jumps and reactive landings. See the vertical program and how to jump higher for basketball articles on this site for the complete approach.
Football (soccer):
Bulgarian split squat and single-leg RDL develop the kicking leg strength and standing leg stability. Single-arm cable press develops the shoulder stability relevant to shielding and contact situations.
Tennis and racket sports:
Single-arm pressing and pulling exercises develop the stroke-specific unilateral upper body strength. Single-leg lateral step-up develops the lateral push-off of court movement.
Combat sports:
Single-arm exercises in all planes develop the striking-specific unilateral upper body power. Single-leg exercises develop the explosive push-off of offensive and defensive footwork.
Frequently Asked Questions
Should I do unilateral or bilateral exercises for building muscle?
Both are effective for muscle building. Research has found that unilateral and bilateral exercises produce similar hypertrophy outcomes when matched for volume and effort. For athletes, the additional benefits of unilateral training (asymmetry correction, balance, sport-specific transfer) make it worth including alongside bilateral work regardless of hypertrophy goals.
Why does my weaker side feel so much weaker than my stronger side?
Side-to-side strength asymmetries are extremely common and develop from dominant-side athletic habits, previous injuries on one side, and the natural handedness or footedness patterns of sport and daily life. Asymmetries of 10 to 20 percent between sides are common in untrained athletes. Regular unilateral training consistently reduces these asymmetries over 8 to 12 weeks as the weaker side catches up.
Can unilateral training replace bilateral training entirely?
Not optimally. Bilateral exercises allow heavier absolute loads that develop maximum strength to a degree that unilateral exercises cannot replicate. Heavy bilateral squats and deadlifts develop the total lower body strength that sets the ceiling for unilateral explosive power. The combination of bilateral strength development and unilateral power transfer training produces better athletic outcomes than either alone.
How do I know if I am ready to add load to unilateral exercises?
The bodyweight version of each unilateral exercise should be mastered before adding external load. Specifically: the single-leg squat should be controlled through a full range without knee cave or balance loss, the single-leg RDL should be smooth without significant hip rotation or trunk lean, and the Bulgarian split squat should feel controlled throughout the range. Once the bodyweight version is consistently clean, begin adding load conservatively.
Is unilateral training good for lower back pain?
Yes. Unilateral exercises develop the hip and core stability that protects the lower back during asymmetric loading. The single-arm farmer’s carry and single-leg exercises specifically develop the quadratus lumborum and gluteal muscles that support the lumbar spine during unilateral loading. Athletes with lower back pain often find that unilateral exercise rehabilitation is more comfortable than bilateral exercises because the lower absolute loads reduce spinal compression while still developing the stabilising muscles.