CHAPTER 2

Lever

A rigid bar that turns about an axis to create movement.

First class lever

A lever with the fulcrum located midway between the effort and the load.

Second class lever

A lever with the load located between the fulcrum and the effort.

Third class lever

A lever with the effort located between the fulcrum and the load.

Fulcrum

The point at which a lever turns or is supported (also known as the axis).

Load

The weight or resistance that the lever must move.

Effort

The force required to move the load (generated by muscles).

Mechanical advantage

The ratio of the load arm to the effort arm in a lever.

Load arm

The distance from the load to the fulcrum in a lever.

Effort arm

The distance from the effort to the fulcrum in a lever.

Flexion

The decrease in angle of the bones at a joint.

Extension

The increase in angle of the bones at a joint.

Abduction

The movement of a limb away from the midline of the body.

Adduction

The movement of a limb towards the midline of the body.

Circumduction

The combination of flexion, extension, abduction, and adduction.

Dorsiflexion

The upward flexion of the foot at the ankle joint.

Plantar flexion

The downward flexion of the foot at the ankle joint.

Rotation

The circular movement where part of the body turns while the rest remains still.

Planes

Imaginary lines that divide the body into different halves for movement.

Frontal plane

Divides the body into front and back sections.

Transverse plane

Divides the body into top and bottom sections.

Sagittal plane

Divides the body into left and right sections.

Axes

Imaginary straight lines around which the body rotates.

Sagittal axis

Runs horizontally through the body from front to back, allowing adduction and abduction.

Longitudinal axis

Runs vertically through the body from head to toe, enabling rotation in an upright position.

Transverse axis

Runs horizontally through the body from left to right at the hips, facilitating flexion and extension.