Bilateral vs Unilateral Exercises: The Case for Single-Leg Training

Should you squat on two legs or one? Press with both arms or alternate? The answer isn't either/or—it's both, used strategically. Here's when and why to use bilateral versus unilateral exercises.

Definitions

Bilateral exercises: Both limbs working together

• Squats, deadlifts, bench press, pull-ups, rows

Unilateral exercises: One limb working at a time

• Single-leg squats, lunges, single-arm rows, split squats

Alternating exercises: Both limbs involved but working independently

• Alternating dumbbell curls, walking lunges, alternating rows

The Bilateral Deficit Phenomenon

Here's something surprising: the sum of what each leg can produce individually often exceeds what both legs produce together. This is the "bilateral deficit."

Example:

• You can leg press 200 lbs with right leg alone
• You can leg press 200 lbs with left leg alone
• But you can only leg press 350 lbs with both legs together (not 400)

Why this matters: You may actually be able to challenge each leg more effectively with unilateral training, especially for strength development.

Benefits of Bilateral Training

1. Heavier Absolute Loads

You can use more total weight with bilateral exercises. A 300 lb squat creates more spinal loading and systemic stress than any single-leg variation.

2. Simpler to Perform

Two feet on the ground is more stable. Easier to focus on the target muscles without balance demands.

3. Time Efficiency

One set works both limbs simultaneously. Faster workouts.

4. Sport Specificity (Some Sports)

Powerlifting, Olympic lifting, and some athletic movements require bilateral strength.

5. Easier to Progress

Adding 5 lbs to a squat is straightforward. Progressing single-leg work can be more complex.

Benefits of Unilateral Training

1. Identifies and Corrects Imbalances

When you squat with both legs, your stronger leg can compensate for your weaker one. Single-leg work exposes the difference.

Example: You might think both legs are equally strong until you try Bulgarian split squats and realize your left leg fails 3 reps earlier than your right.

2. Greater Muscle Activation

Research shows single-leg exercises often produce equal or greater muscle activation despite using less total weight. Each leg works harder.

3. Improved Balance and Stability

Single-leg work challenges proprioception, coordination, and stabilizer muscles that bilateral work doesn't stress.

4. Reduced Spinal Load

For the same muscular challenge, unilateral lower body work puts less load on the spine. Important for those with back issues.

Example:

• Heavy back squat: 315 lbs on spine
• Challenging Bulgarian split squat: 50 lb dumbbells = 100 lbs total

Your legs work hard in both, but your spine is happier with the second option.

5. Sport Specificity (Most Sports)

Running, jumping, cutting, throwing—most athletic movements happen on one leg or one arm at a time. Training that way transfers better.

6. Injury Prevention

Imbalances between limbs are a known injury risk factor. Unilateral training addresses this directly.

7. Work Around Injuries

If one side is injured, you can still train the other side. With bilateral work, you're limited by the weaker/injured side.

When to Prioritize Bilateral Exercises

Maximum Strength Development

If your goal is to lift the most weight possible, bilateral exercises allow heavier loads. Powerlifters need to squat and deadlift with both legs.

Beginners

Mastering bilateral movements first builds a foundation before adding the balance challenge of single-leg work.

Time Constraints

When you only have 20-30 minutes, bilateral exercises are more time-efficient.

Building Overall Size

For pure hypertrophy, bilateral exercises make progressive overload straightforward and accumulate volume efficiently.

When Stability Is an Issue

Some people lack the balance for single-leg work initially. Build up bilateral strength and basic balance first.

When to Prioritize Unilateral Exercises

Athletes (Most Sports)

Running, sprinting, jumping, cutting—these are single-leg activities. Train that way.

Correcting Imbalances

If one side is noticeably weaker or smaller, unilateral work forces the weak side to catch up.

Rehabilitation

Unilateral work lets you:

• Challenge the injured side appropriately
• Train the uninjured side without limitation
• Restore balance between limbs

Back Pain/Spinal Issues

Reducing spinal load while still challenging the legs is valuable. Single-leg work does this.

Functional Goals

Real-world activities are often unilateral. Training that way improves carryover.

Plateau Breaking

If bilateral lifts have stalled, switching to unilateral focus can restart progress.

The Best Unilateral Exercises

Lower Body

Rear-Foot Elevated Split Squat (Bulgarian)

• Excellent quad and glute development
• Balance challenge without instability
• Easy to load heavily

Lunges (Walking, Reverse, Lateral)

• Versatile movement patterns
• Great for hip mobility
• Easy to progress

Single-Leg Romanian Deadlift

• Hamstring and glute focus
• Balance and stability challenge
• Hip hinge pattern

Step-Ups

• Functional climbing motion
• Scalable difficulty (height, load)
• Knee-friendly when done right

Single-Leg Press

• Heavy loading without balance demand
• Good for building base strength
• Easier to isolate quads

Single-Leg Hip Thrust

• Glute-focused
• No spinal load
• Easy to progress

Upper Body

Single-Arm Dumbbell Row

• Back development
• Core anti-rotation
• High loading possible

Single-Arm Dumbbell Press

• Chest and shoulder
• Core stability demand
• Exposes left/right differences

Single-Arm Lat Pulldown

• Isolated lat work
• Feel the muscle more
• Correct imbalances

Single-Arm Overhead Press

• Shoulder strength
• Core stabilization
• Functional pattern

Programming: How to Balance Both

Option 1: Bilateral Main, Unilateral Accessory

Example Workout:

• Squat: 4×6 (bilateral main lift)
• Bulgarian Split Squat: 3×10 each leg (unilateral accessory)
• Leg Curl: 3×12 (bilateral)
• Single-Leg Calf Raise: 3×15 each (unilateral)

Good for: Strength focus, most people

Option 2: Alternate Days

Day A: Bilateral focus

• Squat, Romanian Deadlift, Leg Press

Day B: Unilateral focus

• Lunges, Single-Leg RDL, Step-Ups

Good for: Those with specific unilateral goals

Option 3: Primarily Unilateral

Example Workout:

• Bulgarian Split Squat: 4×8 each leg
• Single-Leg RDL: 3×10 each leg
• Walking Lunges: 3×12 each leg
• Single-Leg Hip Thrust: 3×12 each leg

Good for: Athletes, those with back issues, rehab

Option 4: Unilateral Variation of Bilateral

Replace traditional bilateral exercises with unilateral versions:

• Squat → Split Squat or Rear-Foot Elevated Split Squat
• Deadlift → Single-Leg RDL
• Bench Press → Single-Arm Dumbbell Press
• Rows → Single-Arm Rows

Good for: Imbalance correction, injury prevention

Addressing Common Concerns

"Single-leg exercises are too hard to balance"

Solutions:

• Start with hand support (hold wall or rack)
• Use Smith machine or cables for stability
• Progress gradually: split squat → walking lunge → Bulgarian → single-leg squat
• Build ankle stability and hip strength over time

"I can't load them heavy enough"

Solutions:

• Use dumbbells, barbell, vest, or cable
• Bulgarian split squats can be loaded very heavy
• Single-leg press allows maximal loading
• Tempo manipulation increases challenge without weight

"They take too long"

Solutions:

• Superset left and right sides with minimal rest
• Use alternating exercises (walking lunges)
• Focus unilateral work on weak areas only
• Combine with bilateral work strategically

"My balance is terrible on one side"

Good news: That's exactly why you need unilateral training. The imbalance is the problem, and training exposes it so you can fix it.

Practical Application by Goal

Goal: General Fitness

Mix both. Use bilateral compound movements for efficiency, add unilateral accessory work for balance and stability.

Sample: 2-3 bilateral main lifts + 1-2 unilateral accessories per workout.

Goal: Athletics/Sports Performance

Favor unilateral. Most sports are single-leg dominant. Train accordingly.

Sample: 50%+ of lower body work should be unilateral.

Goal: Powerlifting/Maximal Strength

Favor bilateral. You compete in bilateral lifts. Train them primarily.

Sample: Bilateral main lifts + unilateral accessory for balance.

Goal: Bodybuilding/Hypertrophy

Both work. Muscles don't know if one leg or two is working—they just respond to tension.

Sample: Mix based on weak points and variety.

Goal: Rehabilitation

Often unilateral-focused. Need to assess and correct left/right imbalances, protect the spine, and challenge each limb appropriately.

Sample: Test both sides, address deficits specifically.

Goal: Injury Prevention

Include meaningful unilateral work. Imbalances are injury risk factors.

Sample: Regular unilateral lower body work, at least 1-2 exercises per session.

Testing Your Balance (Left vs. Right)

Periodically test:

Single-Leg Squat (to box/bench)

• How many reps per side?
• Any notable difference in control?

Single-Leg Balance (eyes closed)

• Time each side
• 20%+ difference = imbalance

Single-Leg Hop (for distance or height)

• Any difference between sides?

Single-Arm Push/Pull Strength

• Same weight, same reps on both sides?

If imbalances exist, address with unilateral focus on the weak side.

The Bottom Line

Both bilateral and unilateral exercises have value. The question isn't which is "better"—it's how to use both appropriately for your goals.

Key Principles

1. Include both in a well-rounded program
2. Use unilateral work to expose and correct imbalances
3. Reduce spinal load by substituting unilateral for bilateral when needed
4. Train sport-specifically—most sports are unilateral
5. Don't neglect either extreme

If you've been training only bilateral, add meaningful unilateral work. If you've avoided bilateral heavy lifting, include it. The best programs use both strategically.