Intro.pptx

Intro to Applied Kinesiology Huntington University Nate Short, PhD, OTD, CHT  Objectives  Review relevant principles of physics as they relate to kinesiology  Define relevant terms such as vector, moment arm, & force related to biomechanics  Explore ty...

Intro to Applied Kinesiology Huntington University Nate Short, PhD, OTD, CHT  Objectives  Review relevant principles of physics as they relate to kinesiology  Define relevant terms such as vector, moment arm, & force related to biomechanics  Explore types of levers & common levers found in the body  Introduce concepts of force couples & synergy in biomechanics of the body “Whoever considers the study of anatomy, I believe will never be an atheist; the frame of man's body, and coherence of his parts, being so strange and paradoxical, that I hold it to be the greatest miracle of nature.” Edward Herbert  For we are God’s handiwork, created in Christ Jesus to do good works, which God prepared in advance for us to do. Ephesians 2:10  Functional Anatomy  Anatomical structures that contribute to movement and function  Occupational Therapy Practice Framework (OTPF)  Motor performance skills  Body structures and functions (client factors)  Performance patterns  Habits, roles, routines, rituals  Purposeful motion within a specific environmental context  Impacted by client factors & context (environmental & personal) Common Anatomical Terminology  Kinesiology: study of mechanics of body movements  Biomechanics: the study of the response of biological systems to mechanical forces  Both utilize principles from math, physics, and biology  Vectors represent forces such as joint & muscle actions: Magnitude: length of line Orientation: angular position of line Direction: location of arrowhead Point of Application: location of force (tendon insertion)  Math Review  Vectors can be added & multiplied but not in this class  What you should know:  Direction/orientation of force  2-dimensional analysis of joint motion in a single plane  Forces and Moments  FORCE: a “push” or “pull” from physical contact between two objects  MOMENT: synonymous with “torque”  FORCE acting at a DISTANCE from CENTER OF ROTATION  MOMENT = r (distance) x F (force) MOMENT ARM: perpendicular distance of force from center of rotation  HUH??  At each joint of body, various muscles (forces) are acting on joint (center of rotation) to produce moments (torque) which cause two bones to move in relation to one another (rotation around an axis) Moment Arm: Brachialis  Internal vs. External Moment  Muscles generate internal force (moment) to rotate joints  Gravity or the weight of an object generate external force (moment) on joints as well  Joint Reaction Force: force generated by joints in response to external forces acting upon them  Carrying a briefcase or purse  Lifting or transporting objects  Calculating Joint Reaction Force: Biceps 10 lbs. X. 4 cm At each joint of body 28 cm Ratio of external moment arm/internal moment arm 28:4 = 7:1  Joint Reaction Force  What is the relevance to occupational performance?  Lifting, carrying, transporting objects?  Activity modification, compensatory strategies, prevention?  Muscle Forces in the Body  Prime Mover (agonist): muscle producing the most force for a particular motion  Antagonist: muscle that counteracts specific motion; must relax  Stabilizer/fixator: muscle(s) that stabilize proximal segment or origin of active muscle group (e.g. scapula and clavicle stabilized for humeral elevation (deltoid/supraspinatous)  Synergist: muscle(s) that assist the prime mover to produce specific motion  Force Couple  Muscles may also act with similar force & orientation but in opposite directions to stabilize or move a joint  This is known as a force couple  Example: scapular stabilizers  If these two muscles act as a force couple, what movement is produced?  Static Equilibrium  Sum of all vectors is ZERO – no motion w/ complete balance of forces  Any muscle contraction has an equal & opposite force preventing motion  Follows Newton’s 1st Law: “An object remains at rest unless acted upon by an unbalanced external force”  Example: Holding arm in static position to wash hair  Musculoskeletal Levers  Levers in body are made up of:  Exerted force (effort): muscle acting on joint  Resistive force (resistance): external force (gravity, weight)  Axis: center of rotation (joint – usually)  Increase mechanical advantage (leverage) on joint What is the exerted force? What is the resistive force? What is the center of rotation?  Levers  1st Class: forces on different sides of axis (seesaw)  2nd Class: forces on same side – external force closer to axis than muscle force (wheel barrow)  3rd Class: forces on same side – muscle force closer to axis (shovel) MOST joints in human body act as 3 rd class levers Classify these lever pairings:  Open & Closed-Chain Patterns Microsoft stock images  Center of Gravity (COG)  Definition: point at which weight of an object appears to be concentrated  In anatomical position, COG for human body is at 2 nd sacral vertebra (changes with motion) As we move, the COG changes As we age, our COG moves anteriorly  Clinical Application: Patient Transfers  Uses “lever” to gain mechanical advantage for safe transfer  Body mechanics are key:  Gait belt around waist (between ribs & pelvis)  One foot between patients feet; create “fulcrum”  Back straight lifting with knees  Body weight with reverse propulsion to stand & turn patient  Kinematics  Kinematics: study of motion without regard to force (2-D)  Rotation: one point remains stationary & all other points have arch of motion around static point (Ferris Wheel)  Translation: all points of object move same distance (Moving Train)  Nearly all joint motion in body involves primarily  Kinematics  Rotator cuff action at glenohumeral joint:  As humerus elevates, medial & inferior glide also occur  Gliding occurs from complex action of rotator cuff  Classic example of rotation & translation at a joint  Translation also moves the center of rotation  So what?  Kinematic principles applied when treating individual joints  Normal Pattern vs. Dysfunctional Pattern  Manual treatment techniques utilize mobilization to restore optimal joint kinematics, improve motion & function  This will be discussed more when we discuss pathology  Kinematics  Position: location of a point or object in space  Displacement: distance traveled between two locations  Velocity: displacement over time  Acceleration: changes in velocity over time  Planes of Motion  Sagittal Plane: right & left portions  Most flexion/extension  Frontal Plane: front (anterior) & back (posterior) portions  Most abduction/adduction  AKA: Coronal plane  Transverse Plane: top (superior) & bottom (inferior) portions  Planes and Axes of Motion  How to remember?  Frontal: Front & back portions  Sagittal: Side to side portions  Transverse: Top & bottom portions  Kinetics  Study of motion under action of force  VERY complex topic out of scope of this course  Definitions to know:  Work: force required to move an object a certain distance  Power: rate that work is being done  Energy: capacity to perform work  Potential Energy: stored energy  Kinetic Energy: energy of motion  Mechanical Properties  Extensive Properties: depend on amount of material  Mass: how much matter is in an object  Volume: amount of space an object occupies  Intensive Properties: do not depend on amount of material  Density: mass per unit volume (normalized property)  Stress: load per area (pounds per square inch)  Stress vs. Strain  Stress: units of force acting on specific area  Example: 100 lbs./inch²  Strain: normalized stretch or displacement of a material  Example: Change in length of a rubber band under stress  Stress vs. Strain  Compressive Load: pushing along axis of cylinder  Example: Crushing a soda can  Tensile Load: pulling along axis of cylinder  Example: Stretching out a slinky  Shear Forces  Shear forces occur when materials are moving against one another (rubbing hands together)  Shear forces also produce stress and strain to the material they act upon  Stress-strain testing  Body tissue flexibility varies depending on composition & design  YOUNG’S Modulus – stress/strain slope of material  How much displacement (strain) under increasing force (stress)?  Muscle  Ligament  Tendon  Load to Failure  At what load of stress does body tissue rupture (continuity disrupted)?  This is known as Load to Failure  Largest stress a material can withstand before breaking is called Ultimate Strength  Elastic vs. Plastic  Elastic Deformation  Returns to original size/shape after stress removed  Plastic Deformation  Permanent deformation  Yield Point  Yield Point: amount of stress that causes plastic deformation of a material  Ductile material: A material that YIELDs (plastic deformation) before it BREAKS completely (paper clip)  Brittle material: material that DOES NOT YIELD before it BREAKS completely (dry stick)  Fatigue  Material loaded/unloaded repeatedly beneath yield strength  No outward signs but material is weakened  Fatigue Limit: stress below which material will never fail in fatigue  Paper clip bent with very small motions will never break  Same paper clip bent with large motions will fail quickly  Loading Rate  Rate of loading of material may change behavior of material  Generally, faster material is loaded, more brittle it behaves.  Loading rate is referred to as strain rate or stress rate.  Clinical Ex: The faster a tight muscle is stretched, the more resistance is felt due to reflexive action of muscle to quick stretch  Muscle tissue responds better to low-load, prolonged stretches  Loading Rate and Injury  Load rate also affects behavior of body tissues:  A high load rate to a ligament tends to produce failure in central part of ligament  A low load rate to a ligament may produce an avulsion fracture at tendon insertion  Viscoelasticity  Some solid materials have a fluid-like component that acts on the material over time.  This is called viscoelasticity  Body tissues have varying degrees of viscoelasticity and respond differently to stresses applied to tissues  Torsion and Bending  Bones are “structural supports” of body & subjected to various stressors from external forces  Two forces acting on bones involve:  Torsion: a twisting or torque force  Bending: a force applied to a horizontal “beam” or bone in the body  Clinical Application: Fractures  Many fractures occur as a result of torsional or bending force as bone reaches its ultimate strength  Torsional force may create a spiral fracture whereas a bending force creates a more simple, linear fracture. What type of force might have caused these fractures? Cases courtesy of Frank Gaillard, Case courtesy of Derek Smith, Case courtesy of Mohammad Osama Hussein Radiopaedia.org, rID: 36663 Yonso, Radiopaedia.org, rID: 87507 Radiopaedia.org, rID: 12382  Clinical Application: Tissue Lengthening  External forces are used in therapy process to lengthen tissues:  Creep: deformation of material over time due to constant load  Dynamic splinting – constant load of spring/elastic  Stress Relaxation: stress of material reduced as material is held at a constant deformation  Static progressive splinting – constant deformation/positioning reduces joint/tissue contracture Static-Progressive Orthotics  Summary  External forces are constantly acting on body in form of gravity, weight, objects, etc.  Body is constantly reacting to these forces to maintain balance, mobilize, & perform various tasks  Tissues of body have various biological makeup which causes them to react differently to forces exerted upon them  Forces acting on individual joints can be conceptualized at a basic level as levers with forces acting at a fulcrum  References:  Oatis, C. A. (2009). Kinesiology: The mechanics and pathomechanics of human movement. 2nd ed. Philadelphia, PA: Lippincott,Williams, and Wilkins.  Short, N., Vilensky, J., & Suarez-Quain, C. (2021). Functional Anatomy for Occupational Therapy. Books of Discovery.  Images, unless otherwise cited, are courtesy of Books of Discovery (copyright 2021) and may not be used without expressed written consent