Leverage and Moment Arms: How Biomechanics Affects Your Lifts

Understanding leverage and moment arms explains why certain exercises feel harder at specific positions, why some people are naturally better at certain lifts, and how to modify exercises for your body. This biomechanics guide will help you train smarter.

Basic Physics Concepts

What Is Torque?

Torque is rotational force—the force that causes rotation around a joint:

Torque = Force × Moment Arm

To lift a weight, your muscles must produce enough torque to overcome the torque created by the load.

What Is a Moment Arm?

The moment arm is the perpendicular distance between:

• The line of force (weight pulling down, or muscle pulling)
• The axis of rotation (the joint)

Longer moment arm = more torque for same force

Why This Matters

The same weight creates different demands depending on:

• Joint position (changes moment arm)
• Your body proportions
• Exercise variation

Moment Arms in Common Exercises

The Squat

At the bottom:

• Hip moment arm is longest (hips far from bar)
• Greatest hip torque demand
• This is why the bottom is hardest

At lockout:

• Moment arms are minimal
• Weight is over joints
• Feels easy

Individual differences:

• Long femurs = longer hip moment arm = harder bottom position
• Short torso = more forward lean = even longer hip moment arm
• This is why some people struggle more with squats

The Deadlift

Off the floor:

• Back angle creates long moment arm at hips
• Knee and hip moment arms both significant
• Requires high force production

At lockout:

• Moment arms minimal
• Weight stacked over body
• Much easier

Conventional vs Sumo:

• Sumo: More upright torso = shorter hip moment arm
• Conventional: More forward lean = longer hip moment arm
• Why sumo can feel easier off the floor for some

The Bench Press

At chest level:

• Shoulder moment arm is longest
• Greatest demand on pecs and front delts
• The "sticking point" for most

At lockout:

• Moment arm shortens
• Triceps take over
• Easier portion of lift

Grip width affects moment arms:

• Wider grip = shorter range of motion but longer shoulder moment arm
• Narrower grip = longer range of motion but more tricep involvement

The Overhead Press

At shoulder level:

• Long moment arm at shoulder
• Hardest position

Overhead:

• Weight stacked over shoulder joint
• Minimal moment arm
• Easy to hold

Bicep Curls

At 90 degrees (forearm parallel to floor):

• Maximum moment arm
• Hardest position
• Peak tension on biceps

At top and bottom:

• Moment arm approaches zero
• Minimal tension
• "Rest" positions

Muscle Moment Arms

Muscles also have moment arms—the distance from their line of pull to the joint:

Why This Matters

Larger muscle moment arm = more mechanical advantage

Some people have:

• Naturally larger moment arms for certain muscles
• Better leverage for certain movements
• "Genetic advantages" for specific lifts

Example: The Biceps

• Biceps inserts on the forearm
• Distance from insertion to elbow = biceps moment arm
• Farther insertion = better leverage for curling
• This varies between individuals

Example: The Quads

• Patellar tendon moment arm affects knee extension strength
• Larger moment arm = more mechanical advantage
• Partially explains why some people have naturally strong legs

Practical Applications

Exercise Selection by Moment Arm

Long moment arm exercises (more challenging):

• Stiff-leg deadlift (long hip moment arm throughout)
• Incline curls (biceps stretched, moment arm maintained)
• Front raises (long lever arm)
• Good mornings (challenging hip moment arm)

Short moment arm exercises (easier mechanically):

• Leg press (shorter effective hip moment arm)
• Preacher curls at top (reduced moment arm)
• Lateral raises at bottom (moment arm is zero at start)

Modifying Difficulty with Leverage

To make exercises harder:

• Increase moment arm (move weight farther from joint)
• Use pauses at position of max moment arm
• Slow down through the hardest range

To make exercises easier:

• Decrease moment arm (weight closer to joint)
• Use accommodating resistance (bands/chains)
• Limit range of motion to favorable leverages

Understanding Sticking Points

Sticking points occur where:

• Moment arm is longest
• Mechanical disadvantage is greatest
• Force production is limited by leverage

Solutions:

• Strengthen muscles at that range
• Use partial reps in sticking point range
• Improve technique to optimize leverages

Body Proportions and Exercise Selection

Long Limbs

Challenges:

• Longer moment arms in most exercises
• Greater range of motion required
• More work per rep

Adaptations:

• May need stance/grip adjustments
• Often benefit from partial ROM training
• Sumo deadlift may suit better than conventional

Short Limbs

Advantages:

• Shorter moment arms
• Less range of motion
• Mechanically advantaged in many lifts

Considerations:

• May need to work through fuller ranges intentionally
• Can often handle higher relative intensities

Long Torso vs Short Torso

Long torso:

• More upright in squats (better leverage)
• May struggle with deadlift lockout
• Often suits front squat well

Short torso:

• More forward lean in squats (worse leverage)
• Usually strong deadlift lockout
• May suit low bar squat better

Long Femurs vs Short Femurs

Long femurs:

• Greater forward lean in squat
• Longer hip moment arm
• May suit wide stance or sumo
• Often better at hip hinge movements

Short femurs:

• More upright squat
• Shorter hip moment arm
• Often naturally good squatters
• May need extra hip work

Optimizing Technique Using Leverage

Squat Technique

Bar position:

• High bar: More upright, longer knee moment arm
• Low bar: More forward lean, longer hip moment arm
• Choose based on your proportions and goals

Stance width:

• Wider: Reduces effective femur length, more upright
• Narrower: More knee travel, more quad-dominant

Depth:

• Below parallel: Longest moment arms, hardest
• Parallel: Moderate moment arms
• Quarter squat: Shortest moment arms, easiest (but least effective)

Deadlift Technique

Stance:

• Conventional: Longer hip moment arm at start
• Sumo: Shorter hip moment arm, more upright
• Choose based on proportions and strengths

Hip position:

• Higher hips: More back involvement (longer moment arm)
• Lower hips: More leg involvement (shorter moment arm at hips)

Bench Press Technique

Arch:

• More arch: Reduces range of motion, decreases moment arm at bottom
• Flat: Full range, longest moment arm at chest

Grip width:

• Wider: Shorter ROM, longer shoulder moment arm, more pec
• Narrower: Longer ROM, more tricep involvement

Elbow position:

• Flared: Longer moment arm for pecs
• Tucked: Reduces shoulder moment arm, protects shoulders

Programming Considerations

Full Range of Motion Importance

Training through full ROM:

• Strengthens muscles at various moment arms
• Builds strength at mechanically disadvantaged positions
• Transfers better to sport and life

Strategic Partial Reps

Partials can target specific moment arm positions:

• Board press: Reduced shoulder moment arm
• Pin squats: Start from bottom (longest moment arm)
• Rack pulls: Reduced hip moment arm

Use for:

• Overloading strong ranges
• Building confidence with heavier weights
• Working around injuries

Accommodating Resistance

Bands and chains match resistance to leverage:

• More resistance at lockout (where you're strongest)
• Less resistance at bottom (where moment arm is longest)
• Creates more even challenge throughout ROM

Key Takeaways

1. Torque = Force × Moment Arm—longer moment arms require more force
2. Exercises are hardest where moment arm is longest (usually bottom positions)
3. Your body proportions affect which exercises suit you best
4. Sticking points occur at positions of mechanical disadvantage
5. Technique modifications can optimize your leverages
6. Exercise selection can target specific moment arm positions
7. Full ROM training builds strength across all moment arms
8. Understanding leverage helps you train smarter, not just harder

Biomechanics isn't just academic—it explains why exercises feel the way they do and how to optimize your training for your individual body.