PS 1001:03 Lecture Notes - Lecture 5: Biceps, Mechanical Advantage, Metatarsal Bones
Review basic biomechanical terminology
e.g. like a seesaw
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Lever = rigid body with 2 externally applied forces (generally one by muscle and one by contact with the environment or gravity)
and a point of rotation (joint)
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Levers
First class lever
Forces on different sides of the centre of rotation (COR)/fulcrum/point of rotation
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Screen clipping taken: 11/03/2018 7:04 PM
e.g load = book in hand, force = muscles
Spine is the fulcrum
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Head = load
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Action of muscle = force
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e.g. head and neck
2nd
Screen clipping taken: 11/03/2018 7:04 PM
Screen clipping taken: 11/03/2018 7:04 PM
Wheel = COR
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e.g. lifting wheelbarrow
Oatis ch 7
L1 - Basic biomechanical principles
Sunday, 11 March 2018
7:00 PM
week 3 Page 1
Wheel = COR
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Weight = load in barrow
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Muscle action = force
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Metatarsals = COR
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Weight of body = load
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Force of muscle = force
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e.g. standing on toes
3rd
Screen clipping taken: 11/03/2018 7:05 PM
Most common in human body, provides greater speed of movement
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Screen clipping taken: 11/03/2018 7:07 PM
Carrying book = load
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Biceps brachii muscles - force
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e.g. elbow = COR
Review the basic math, force and moment definitions and levers required for basic
biomechanical concepts
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Screen clipping taken: 11/03/2018 7:08 PM
1st class
MA = 1
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Mechanical advantage
NB load arm is same as
resistance arm
Effort arm = where muscles
are
week 3 Page 2
MA = 1
Screen clipping taken: 11/03/2018 7:08 PM
2nd class
MA = 2/1 > 1
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3rd class
MA = 1/2 < 1
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Screen clipping taken: 11/03/2018 7:11 PM
Muscles apply force via their tendons to rigid rods (bones) that move around fixed points called fulcrums (joint centres)
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Resistance is based on weight of the segment (plus an object)
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Anatomical levers
Review rotary and stabilising/dislocating components of muscle moment
A moment is caused by a force (F) acting at a distance (r) from the centre of rotation COR of a segment
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Red arrow is biceps brachii
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Moment arm is yellow, perpendicular distance, depends on how much flexion/extension of the elbow
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Orange cross = elbow
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If lifting arm
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Moment arm/lever arm
week 3 Page 3
Document Summary
Lever = rigid body with 2 externally applied forces (generally one by muscle and one by contact with the environment or gravity) and a point of rotation (joint) e. g. like a seesaw. Forces on different sides of the centre of rotation (cor)/fulcrum/point of rotation. Screen clipping taken: 11/03/2018 7:04 pm e. g load = book in hand, force = muscles e. g. head and neck. Screen clipping taken: 11/03/2018 7:04 pm e. g. lifting wheelbarrow. Muscle action = force e. g. standing on toes. Most common in human body, provides greater speed of movement. Screen clipping taken: 11/03/2018 7:07 pm e. g. elbow = cor. Review the basic math, force and moment definitions and levers required for basic biomechanical concepts. Nb load arm is same as resistance arm. Effort arm = where muscles are week 3 page 2. Muscles apply force via their tendons to rigid rods (bones) that move around fixed points called fulcrums (joint centres)
