2 - Biomechanics

2 - Biomechanics - Foundations of Occupation: Foundations...

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Unformatted text preview: Foundations of Occupation: Foundations Kinesiology Biomechanics Lecture 2 Summer 2010 Overview Biomechanics Defined: Kinematics and Kinetics Kinematics: Planes and axes, types of motion, roll and slide mechanics, open- and closed-chain motion, active and passive motion. Forces And Force Vectors Newton’s Laws Mechanical Analysis of Force – Force Systems Analysis of Levers and Mechanical Advantage Torque Kinetics: BIOMECHANICS BIOMECHANICS Kinematics – description of motion of the motion body without regard to forces (type, location, direction, magnitude and rate/duration) direction, Planes Axes Axes Types of motion: axial (rotation) and non-axial Types (translation) (translation) Kinetics - the analysis of forces that produce forces motion or maintain equilibrium motion Forces, vectors and line of pull Biomechanical levers Torque Kinematics Review: Planes & Axes 3 Planes and Corresponding Axes: Sagittal plane around X axis Flexion, extension, hyperextension, plantarflexion & dorsiflexion Transverse/Horizontal plane around Y axis Supination, pronation, internal and external rotation Frontal plane around Z axis ABduction, aDdduction, lateral flexion, reduction of lateral flexion, hyperabduction, hyperadduction Degrees of Freedom: Refers to number of planes of motion within which a joint is able to move (1, 2 or 3 degrees of freedom) TYPES OF “BODY” MOTION TYPES Axial (rotatory, circular, rotation) Axial motion motion Rolling Spinning Non-Axial (translatory, linear) motion Gliding: rectilinear or curvilinear Visuals: Roll, Glide, Spin Rotatory (Axial) Motion Rotatory Movement of an object or Movement segment around a fixed axis in a curved path curved Each point on the object Each or segment moves through the same angle, same at the same time, at a same constant distance from the axis of rotation axis Roll and Spin Translatory (Non-Axial) Motion Translatory The movement of an object or segment in The a straight line. Gliding. straight Gliding. Any point on the object moves through the same distance, at the same time, in same parallel paths. parallel Example: Forearm sliding on table Curvilinear Motion Curvilinear As a bony segment is both rotated on its own As axis and translated forward by rotation at other joint axes, points on that lever can move in a smooth or irregular parabolic path By some definitions = a combination of rotary and translatory motion and **Most common type of movement in the human **Most body. body. Roll and Slide Mechanics Roll Convex-on-Concave Rule: When a convex joint surface moves on a concave joint surface, the roll and slide occur in the opposite direction. Concave-on-Convex Rule: When a concave surface moves on a stationary convex surface, the roll and slide occur in the same direction. Roll & Slide Mechanics Visual Open-Chain and Closed-Chain Motion Open-Chain Open-Chain: Movement of distal segment on a relatively fixed proximal segment. Closed-Chain: Movement of proximal segment about a relatively fixed/stationary distal segment. Active and Passive Motion Active Regardless of type of motion… Can classify as active or passive. Active Motion: generated by active muscles – individual moving joint with associated muscles. Passive Motion: generated by something other than muscle activation, i.e. gravity, another person, another part of the person’s body, etc. Kinetics Kinetics Forces, Vectors and Line of Pull Newton’s Laws of Motion Biomechanical Levers Torque FORCES: Definitions and Components Definitions May be defined as a PUSH - causing compression A PULL - causing tension between two surfaces May INITIATE a motion or STOP a motion May PREVENT a motion May be EXTERNAL or INTERNAL FORCES: Definitions and Components Definitions Force Vector: a pictorial representation of the point of application, direction and magnitude of a force Point of Application – the exact point at which the force is being applied Direction - the line of force Magnitude - the quantity of the force that is being exerted NEWTON’S LAWS OF MOTION NEWTON’S Law of Inertia Law of Acceleration Law Law of Reaction Law Law of Inertia Law Every object persists in its state of Every rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed on it. that Law of Acceleration Law The acceleration of an object is The proportional to the unbalanced forces acting on it and inversely proportional to the mass of that object. object. Acceleration = Force/Mass Force = Mass X Acceleration Law of Reaction Law For every action, there is an equal For and opposite reaction and Force Vectors: Force Bone RESOLUTION OF FORCES RESOLUTION Axial (rotation) vs. Non-Axial (translation) forces Compression forces Distraction Forces Pure rotation occurs when Pure rotation line of pull is at 90 degree 90 angle to part being moved angle RESOLUTION OF FORCES < 90 degree angle (between moving lever and line of pull) compression > 90 degree angle (between moving lever and line of pull) distraction MECHANICAL ANALYSIS OF FORCE MECHANICAL 1. Linear Force Systems 2. Concurrent Force Systems 3. Parallel Force Systems a. Force Couple Mechanical Analysis Of Force Mechanical 1. Linear Force Systems… Linear …2 or more forces act upon an object in the same or line, roughly the same point of application line roughly same e.g. Gastrocnemius / soleus Psoas / iliacus Psoas Mechanical Analysis of Force Mechanical 1. Concurrent Force Systems… …two or more forces act at a common point two of application but in divergent directions of divergent e.g. Pectorals, Deltoids Mechanical Analysis of Force Mechanical 1. Parallel Force Systems… …two or more parallel forces act on the two same object but at some distance from each other other e.g. Hand holding a ball…ball and gravity e.g. pulling forearm down & muscle pulling arm up up Mechanical Analysis of Force Mechanical 3a. Force Couple… • …when two or more when forces act in equal but opposite direction but resulting in a turning turning effect effect (example motion: (example two hands turning a steering wheel) steering ANALYSIS OF LEVERS ANALYSIS Rigid bar that is being acted upon by Rigid parallel forces that cause it to move in a parallel rotary motion. rotary All levers have four components: A rigid bar (bone in the body) An axis or fulcrum, point of rotation (joint) (A) An effort force (E) E A resistance force (R) A R Effort Force = that which is attempting to cause motion cause Resistance Force = that which is Resistance attempting to resist motion attempting CLASSIFICATION OF LEVERS CLASSIFICATION First Class Lever: Effort force and resistance force are on either side of the axis E ____________R A First-Class Lever First-Class E-A-R Effort Force (causes movement) Resistance Force (opposes movement) E Effort Arm A Resistance Arm AXIS R First-Class Lever: CLASSIFICATION OF LEVERS CLASSIFICATION Second Class Lever: Effort force and resistance force are on same side of axis. Resistance force lies between the effort force and the axis of rotation. _______R___________E A Second-Class Lever Second-Class A-R-E Effort Arm Resistance Force (opposes movement) A Resistance Arm AXIS R E Effort Force (causes movement) Second-Class Levers: CLASSIFICATION OF LEVERS CLASSIFICATION Third Class Lever: Effort force and resistance force are on same side of axis. Effort force lies between the resistance force and the axis of rotation. ____E_________R A Third-Class Lever Third-Class A-E-R Resistance Arm Effort Force (causes movement) A Effort Arm AXIS E R Resistance Force (opposes movement) Third-Class Levers: 1st 2nd 3rd MECHANICAL ADVANTAGE MECHANICAL Measures the efficiency of the lever Measures efficiency a RATIO between the effort arm (force) and RATIO resistance arm (force) resistance Relative effectiveness of the effort force compared to the resistance compared Larger the effort force arm relative to the Larger resistance force arm, the better the mechanical advantage mechanical MECHANICAL ADVANTAGE (MA) MECHANICAL distance of effort arm (EA) = distance of resistance arm (RA) distance When MA > 1 then good MA When ex: 2nd class levers ex: When MA < 1 then poor MA ex: 3rd class levers ex: First-Class Levers and Mechanical Advantage First-Class TORQUE TORQUE The ability of a force to cause rotation of the The lever. lever. Known as “moment of force” Known Rotation of a lever depends on magnitude of the force and distance of force from the axis force Calculate Torque – multiply the perpendicular Calculate distance from the muscle’s line of action to the distance axis of motion axis Perpendicular distance = Moment arm Perpendicular Moment TORQUE TORQUE T = (f) d Torque: Assuming Muscle A and Muscle B have the same amount of force, Muscle B would have greater Torque (ability to rotate the arm/flex the elbow joint) because of the longer Moment Arm (Perpendicular Distance between axis and line of pull) Moment Arms Torque of Gravity Bone or boney prominence that changes Bone the direction of pull of a muscle (and therefore changes moment arm). therefore APPLYING TORQUE: APPLYING ANATOMICAL PULLEYS PULLEYS Patella Lateral Malleolus Lateral (gracilis) (gracilis) ...
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