Classes of Levers

Anatomical Position

Erect body posture with face and palms forward.

Cardinal Planes

Three primary planes: frontal, sagittal, transverse.

Frontal Plane

Divides body into anterior and posterior sections.

Sagittal Plane

Divides body into right and left sections.

Transverse Plane

Divides body into upper and lower sections.

Anterior-Posterior Axis

Axis around which frontal plane movements occur.

Medial-Lateral Axis

Axis around which sagittal plane movements occur.

Vertical Axis

Axis around which transverse plane movements occur.

Class 1 Lever

Fulcrum between effort and resistance; few in body.

Class 2 Lever

Resistance between fulcrum and effort; longer effort arm.

Class 3 Lever

Effort between fulcrum and resistance; shorter effort arm.

Wheelbarrow

Example of a class 2 lever in use.

Elbow Flexion

Example of a class 3 lever in action.

Shoulder Abduction

Class 3 lever with weight at the wrist.

Triceps Brachii

Muscle involved in class 1 lever action.

Seesaw

Common example of a class 1 lever.

Abduction

Movement away from the body's midline.

Adduction

Movement toward the body's midline.

Flexion

Decreasing the angle between body parts.

Extension

Increasing the angle between body parts.

Medial Rotation

Rotation towards the body's midline.

Lateral Rotation

Rotation away from the body's midline.