1.) Mechanical Advantage - the relationship or ratio of the moment arm to which force applied
(effort) acts to that through which a resistive force (resistance) acts. This means that the
muscular effort must be greater than the resistive force to create motion. If the effort (muscle
contraction) is greater than the resistance (work needed to be done) then there will be
motion applied.
A.) Ideal Mechanical Advantage (IMA) - represents the theoretical magnification of
force if no energy is lost in the form of heat due to friction.
B.) Actual Mechanical Advantage (AMA) - represents the actual magnification of useful
force after friction losses.
2.) Fulcrum - a lever’s pivot point, or axis of rotation.
3.) Moment Arm (M)- the perpendicular distance from the force to the fulcrum, can be depicted
as either the effort moment arm or the resistance moment arm.
4.) Torque - magnitude of force times the length of the moment arm, or the force applied around
an axis of rotation.
M x RA = total torque
5.) Muscular effort - the muscular force created by the musculoskeletal system that creates
contraction of the tissue
6.) Resistive Force - the work being applied to the lever; the outside source that acts opposite
to muscular contraction. As you move closer to the line of gravity, the resistance will
get smaller.
7.) Resistance area - the distance from the line of gravity to the load.
8.) Force arm(FA) - the distance from the center of the joint to the muscle insertion.
9.) Resistance arm(RA) – distance between fulcrum and point of resistance.
Class I levers