Kinesiology Biomechanics

machines in body

levers, wheel axels, pulleys

levers

rotate about an axis as a result of force being applied to cause its movement against resistance

axis

fulcrum, point of rotation, commonly the joint

effort

point of force application, usually muscle insertion

resistance

center of gravity or external resistance

1st class lever

EAR, axis in the middle, balanced movements (seesaw)

2nd class lever

ARE, resistance somewhere between axis and effort, produces force advantage

3rd class lever

AER, effort somewhere between axis and resistance, most common, produce speed/range advantage

moment arm

MAe or MAr, the perpendicular distance between the line of action of effort and the axis

mechanical advantage

MA = resistance divided by effort

force advantage lever

do not need as much force, MAe > MAr then mechanical advantage is >1

speed range lever

need more force, MAr > MAe then mechanical advantage is <1

torque

rotary effect created by an applied muscles effort