Musculoskeletal System

• Lever- movable bar that pivots on fulcrum attached to fixed point.

• The human body can be modeled as a system of levers

• Range of Motion- the distance or angle through which the load moves when the level is activated

• Force effect- how a lever system can either amplify the force applied or reduce the effort needed to move a load

Class 1: effort and load are on opposite sides: Neck

Class 2: load is closer to fulcrum: calf muscle

Class 3: effort is closer than load to fulcrum: bicep muscle

Law of lever- when balanced, force at one end is multiplied by distance from fulcrum is equal to the force at the other end multiplied by its distance from fulcrum.

Muscle is attached to bone at two points:

Origin site- the immovable point

Insertion site- movable point

• when muscle contracts, insertion moves toward origin

• In most cases, origin and insertion are located on opposite sides of joint

Parallel muscle fibers- ROM

• strap

• Fusiform

• Convergent

Pennate muscle fibers- force production

• uni

• Bi

• Multi