THE LEVER SYSTEMS

A lever system is a mechanical system that maximizes and minimizes the effect of forces applied through it. Due to levers, the human body is capable of performing a wide range of motions.

Components of a Lever

1. Motive Force (usually muscle, but not always)
2. Resistance Force (weight, acceleration, deceleration, change of direction)
3. A fulcrum or axis (articulation, joint)
4. The Rod (lever) -- a rigid shaft (bone)
5. Force Arm (distance from motive force application to axis)
6. Resistance Arm (distance from resistive force application to axis)

Results of Using a Lever (What does it do?)

1. Provides Mechanical Advantage
2. Increase of ROM (range of motion)

Practical Implications of Using a Lever

• It can multiple forces (by either maximizing or minimizing the motive or resistive force).
• It can enhance the speed an object or limb can be moved.
• It can change the direction of force or "energy."

Types of Levers "ARF"

Type I AXIS in the middle (mechanical advantage, increased ROM, & speed)
{e.g., teeter-totter, pry-bar on piece of wood, shoveling}

Type II RESISTANCE in middle (mechanical advantage)
{nut cracker, wheel barrow}

Type III FORCE in the middle (increased ROM & speed)
{batting, racket sports}