Chapter 5 – Torque

What is torque?

A twisting or rotational force that causes rotation around an axis of rotation.

What is the formula for torque?

T = F × r (where T = torque in Nm, F = force in N, r = moment arm in m).

What are the units for torque?

Newton-meters (Nm).

What is the moment arm?

The perpendicular distance from the axis of rotation to the line of action of the force.

How can you increase torque if the force stays the same?

Increase the moment arm length.

How can you increase torque if the moment arm stays the same?

Increase the applied force.

What three factors influence torque?

1) Position of force relative to the axis of rotation 2) Distance from the axis (moment arm) 3) Magnitude of the force.

What is external torque?

Torque created by outside forces like gravity, weights, or resistance.

What is internal torque?

Torque generated by muscles contracting to oppose external torque.

During a bicep curl, what produces external torque?

The weight of the dumbbell acting downward.

During a bicep curl, what produces internal torque?

The biceps muscle pulling upward on the forearm.

What determines how strong a muscle feels in a certain position?

The joint angle and length of the muscle's moment arm.

What is Lombard's Paradox?

When opposing muscles (quads and hamstrings) contract together—each winning at its own joint due to a longer moment arm.

In Lombard's Paradox, which muscles win at the hip and knee?

Hamstrings win at the hip (longer moment arm); Quads win at the knee.

How do torque demands change in squat variations?

Front squat → more knee torque; Low-bar squat → more hip torque; High-bar → balanced.

What is static equilibrium?

A state where all forces and torques equal zero—no motion occurs.

What is the equation for static equilibrium?

ΣF = 0 and ΣT = 0.

What is the center of mass?

The point where the body's mass is evenly balanced in all directions.

What happens to the center of mass when you move your limbs?

It shifts depending on limb position.

Why do longer tools like wrenches or bats make rotation easier?

A longer moment arm increases torque, allowing greater rotational effect with the same force.