Advantage of second-class levers
They give mechanical advantage and are good for moving heavy loads.
Disadvantage of second-class levers
They usually produce less speed and range of motion.
Advantage of third-class levers
They produce high speed and large range of movement, which is useful in sport.
Disadvantage of third-class levers
They operate at mechanical disadvantage and require greater effort.
Plane
An imaginary flat surface through which movement takes place.
Axis
An imaginary line around which the body rotates.
Frontal plane
A vertical plane dividing the body into front and back.
Sagittal plane
A vertical plane dividing the body into left and right.
Horizontal / transverse plane
A horizontal plane dividing the body into upper and lower sections.
Longitudinal axis
A vertical axis running from head to toe.
Transverse axis
A horizontal axis running from side to side.
Frontal / anterior-posterior axis
A horizontal axis running from front to back.
Flexion
A movement that decreases the angle at a joint. Example: bending the elbow.
Extension
A movement that increases the angle at a joint. Example: straightening the knee.
Abduction
Movement away from the midline of the body. Example: raising the arm sideways.
