Angle of pull PDF

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Angle of pull...

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Describe the angle of pull with examples 90 degree, less than 90 degree and more than 90 degree. Angle of pull is the angle between line of pull of the muscle and bone on which it inserts on.When drawing the line of pull, the direction must always from the insertion point to the origin point.Angle of pull changes when the degree of movement changes.Also, the force needed to undergo a movement depends on the angle of pull. For example, elbow flexion.

There is always a vertical component which perpendicular to the bone which the muscle insert. This component is also known as rotary component.When the elbow flex exactly 90 degree,the line of pull of biceps brachii equal to rotary component.(red arrow)Thus, 100% of force is contributing with rotary force to the movement.

In this situation,the angle of pull less then 90 degree (which located between red arrow and purple arrow).Beside the rotary component(blue arrow),there is another component(purple arrow) of force acting on it.As the angle of pull less than 90 degree,it become stabilizing force as it direct to the joint.

In this situation,,the angle of pull more then 90 degree.Beside the rotary component(blue arrow),there is another component(green arrow) of force acting on it.As the angle of pull more than 90 degree,it become dislocating force as it directed away from the joint....