B.1.4 Levers in Movement and Sport

Lever

A rigid rod that can rotate about a fixed pivot when force is applied.

Fulcrum

The fixed pivot point around which a lever rotates; also known as a pivot.

Moment Arm

The perpendicular distance at which a force acts from the axis of rotation (fulcrum).

Load Arm

The distance at which the load acts from the fulcrum.

Effort Force

The distance at which the effort acts from the fulcrum.

Mechanical Advantage (MA)

How much the effort force is multiplied by to overcome the load; calculated as length of effort arm divided by length of load arm.

First Class Lever

A lever where the effort force and load force are on opposite sides of the fulcrum.

Second Class Lever

A lever where the effort force and load force are on the same side of the fulcrum, with the effort arm longer than the load arm.

Third Class Lever

A lever where the effort and load force are on the same side of the fulcrum, with the effort arm smaller than the load arm.

Effort Arm

The part of the lever arm where the effort force is applied.

Load Force

The weight or resistance that is being moved or supported by the lever.

Range of Motion

The extent of movement around a joint, which can be enhanced in lever systems.

Example of First Class Lever

Muscles of the neck providing the effort force to overcome the load force of the head.

Example of Second Class Lever

Calf muscles contracting to provide effort force when standing on the toes.

Example of Third Class Lever

Biceps brachii providing effort force at the elbow joint to hold a weight at the hand.

Levers Outside the Body

External levers like a baseball bat can enhance physical performance by optimizing speed, power, and control.