iphy 4540 biomechanics
DESCRIPTION
IPHY 4540 Biomechanics. Objective: to learn how to quantitatively analyze the mechanical function of the human musculoskeletal system using principles of physics and physiology. Topics: Functional Anatomy Tissue Biomechanics (muscle, tendon, bone) Movement (kinematics) - PowerPoint PPT PresentationTRANSCRIPT
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IPHY 4540 Biomechanics
• Objective: to learn how to quantitatively analyze the mechanical function of the human musculoskeletal system using principles of physics and physiology.
• Topics:– Functional Anatomy– Tissue Biomechanics (muscle, tendon, bone)– Movement (kinematics)– Movement dynamics (kinetics)
• Whole body, muscle and joint forces• Impulse, Momentum• energy, power• torque
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Outline
• Functional Anatomy• Muscle actions• Lever systems in the body
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Functional Anatomy
• the study of body components needed to achieve or perform a human movement or functions. – Care about movement produced by muscle group, not
muscle location
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Functional Anatomy
Hammill J, Biomechanical Basis of Human Movement
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• Terms– superior– Inferior– anterior– posterior– medial– lateral– proximal– distal– superficial– deep– unilateral– ipsilateral– contralateral– bilateral
Hammill J, Biomechanical Basis of Human Movement
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Functional Anatomy• Reference System
– origin– axes– planes
• Planes– Frontal
• Vertical• Anterior/posterior parts
– Sagittal• Vertical• Left/right parts
– Transverse• Horizontal• Superior/inferior
Hammill J, Biomechanical Basis of Human Movement
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Functional Anatomy• Reference System
– origin– axes– planes
• Planes– Frontal
• Vertical• Anterior/posterior parts
– Sagittal• Vertical• Left/right parts
– Transverse• Horizontal• Upper/lower
Hammill J, Biomechanical Basis of Human Movement
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• Axes: – Longitudinal (Twist):
• head to toe
– Mediolateral (Somersault)• Left to right
– Anteroposterior (Cartwheel)• Front to back
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The knee
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Muscle Actions
• Motors that move our limbs• Example:
– Push-up• Which muscle?• Which joint?• Flexion/extension?
– Leg curl
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Muscle Actions
Muscles: - only exert pulling forces- 3 actions: can exert force and
-shorten (shortening/concentric)-stay the same length (isometric)-be lengthened or resist stretching
(lengthening/eccentric)
- when not activated, muscles can be passively lengthened by other forces
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Shortening Muscle Actions
Isotonic = constant force (artificial)
Isovelocity = constant velocity (artificial)
Neither, i.e. variable force and velocity (most common)
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Isometric Muscle Actions
Muscle produces force, but does not overcome external load, so no movement develops.
Very common: examples?
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Lengthening Muscle Actions
Muscles only exert pulling force,
But the opposing force can be greater than the muscle force, forcibly stretching the muscle.
Also very common.High Risk for injuryExamples:
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Leg press example
• What is the primary muscle involved?• Describe its actions throughout one cycle.
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Muscle Actions
- only exert pulling forces- 3 actions: can exert force and
-shorten (shortening/concentric): force>load-stay the same length (isometric): force=load-be lengthened or resist stretching (lengthening/eccentric)
force<load
Force > load Force = load Force < load
Force
Load
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Outline
• Functional Anatomy• Muscle actions• Lever systems in the body
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Levers
• A method of transmitting force– Amplify force– Amplify velocity– Amplify movement distance
• Muscles use leverage to generate movement
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Levers
• 4 components– Lever (bone)– Fulcrum (pivot point, joint))– Effort force (muscle force)– Load force (external forces)
load
fulcrum
lever
effort
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Levers: The Law
• Law of Levers:– Fload x rload = Feffort x reffort
– r is the distance to the forces
“Give me a lever and I shall move the earth” – Archimedes
Mechanical Advantage: Fload/Feffort > 1, rload < reffort
Mechanical Disadvantage: Fload/Feffort < 1, rload > reffort
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Levers: The Law
• Fload rload = Feffort reffort
A vs B: Mechanical Advantage or Disadvantage? Fload/Feffort = ?
100kg
B
A
F
rload=1mFeffort=my laptop (2kg)
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Levers: 3 classes
Don’t worry about first, second, third classDo understand:fulcrum = joint = pivotThe relative positions of muscle force, joint and
load are important.What is being amplified? Force or velocity
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3 classes of levers
Classes of Levers1. 1st Class— see-saw
2. 2nd Class—Wheelbarrow
3. 3rd Class—Tweezers
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Levers: Force and Velocity
– Fload x rload = Feffort x reffort
• Class 1– Fload x rload = Feffort x reffort
• If rload>reffort
• Fload< Feffort velocity amplifier
• If rload<reffort
• Fload>Feffort force amplifier
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1st Class Levers
Muscle joint load (MJL)
Load joint Muscle (LJM)
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1st Class Lever
Muscle joint load
e.g. triceps acting at the elbowVelocity or force magnifier?
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1st Class Levers
Muscle joint load
e.g. your head is tilting forward (e.g. sleeping)Muscles on the back of the neck pull
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1st Class Levers (MJL) in the body
Amplify velocity of joint extension
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1st Class Levers (MJL) tools
Can amplify force or velocity depending on length of the lever
e.g. tool that amps force using 1st class lever
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1st Class Levers (MJL) tools
Can amplify force or velocity depending on length of the lever
e.g. tool that amps velocity using 1st class lever
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Class 3 levers (JML)
– Fload x rload = Feffort x reffort
• Class 3– Fload x rload = Feffort x reffort
• rload>reffort
• Fload< Feffort velocity amplifier
Joint Muscle Load
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3rd Class Levers
joint muscle load
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3rd Class Levers
joint muscle load
e.g. hold weight in your hand, biceps pulls up
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3rd Class Levers (JML) tools
Can only amplify velocity
e.g. field hockey stick, golf putter, shovel
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Class 2 levers (JLM)
• Class 2– Fload x rload = Feffort x reffort
• rload<reffort
• Fload> Feffort force amplifier
Rare in the body
Jaw joint (using molars) is a good example
Any others?
Joint Load Muscle
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2nd Class Levers (JLM) tools
Can only amplify force
e.g. nut cracker
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Summary
Classes of Levers1. 1st Class— see-saw, push-up
– Muscle-Joint-Load– Force or Velocity amplifier,
depending on the lever arm
2. 2nd Class—Wheelbarrow– Joint-Load-Muscle– Force Amplifier
1. 3rd Class—Tweezers, biceps-curl – Joint-Muscle-Load– Velocity Amplifier
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• Why do we usually see 3rd class levers in the body?
OR• Why do we have short muscle arms?
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Anatomical Terms• Joint Position
– To discuss joint position we define joint angle
– joint angle: relative angle between two segments
• Joint Movement– Flexion: relative angle (joint
angle) decreases– Extension: relative angle
increases (straightening movement)
Hammill J, Biomechanical Basis of Human Movement
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More muscle terms
agonistmuscles creating the same joint movement
antagonistmuscles opposing or producing the opposite joint movementmust relax to allow a movement to occur ORcontract to slow a movement downexample: kicking
co-contraction
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1 joint vs. 2 joint muscles
Examples of 1 joint muscles:
Examples of 2 joint (biarticular) muscles:
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Biarticular muscles
• Advantages
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How do we stand up from a chair?
Joint actions:What muscles act across the hip?What muscles act across the knee?What muscles act across the ankle?All 1-joint muscles? All 2-joint muscles?