biomechanics lecture (ch. 4) and intern resources... · shoulder press, squat shear (side -to...
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BiomechanicsBiomechanics
Chapter 4Chapter 4
Functional AnatomyFunctional Anatomy
The structure and function of the The structure and function of the
““musculoskeletal machinemusculoskeletal machine””
�� Skeletal & Neuromuscular aspectsSkeletal & Neuromuscular aspects
�� Not Cardio, Respiratory, Digestive Systems, etc.Not Cardio, Respiratory, Digestive Systems, etc.
KinesiologyKinesiology
Examines the mechanisms through which the Examines the mechanisms through which the
components of the musculoskeletal system components of the musculoskeletal system
interact with each other and the external world interact with each other and the external world
to perform work and produce movementto perform work and produce movement
The study of movementThe study of movement
Anatomic OrientationAnatomic Orientation
Anatomical position Anatomical position
Planes (figure 1)Planes (figure 1)�� SagittalSagittal –– left & right sections left & right sections
Extremities: flexion & extensionExtremities: flexion & extension
Vertebral Column: flexion & extensionVertebral Column: flexion & extension
�� FontalFontal –– front & back sectionsfront & back sectionsExtremities: abduction & adductionExtremities: abduction & adduction
Vertebral Column: right & left Vertebral Column: right & left sidebendingsidebending
�� Transverse/HorizontalTransverse/HorizontalExtremities: abduction & adduction AND transverse/horizontal Extremities: abduction & adduction AND transverse/horizontal abduction & adductionabduction & adduction
Vertebral Column: right & left rotationVertebral Column: right & left rotation
Neural SystemNeural System
Motor unit Motor unit –– a motor neuron and the muscle a motor neuron and the muscle
fibers it innervates (figure A1)fibers it innervates (figure A1)
�� InnervationInnervation ratio and example (Eye vs. Quad)ratio and example (Eye vs. Quad)
ProprioceptorsProprioceptors ((““feedback systemfeedback system””) ) –– detect detect
stimuli and provide movement controlstimuli and provide movement control
�� Example (fig. A2 and A3) Example (fig. A2 and A3) –– GTO, SpindlesGTO, Spindles
Skeletal SystemSkeletal System
Axial skeletonAxial skeleton�� Skull, vertebral column, sternum & ribsSkull, vertebral column, sternum & ribs
AppendicularAppendicular skeletonskeleton�� Shoulder girdle, pelvic girdle, upper extremity & lower Shoulder girdle, pelvic girdle, upper extremity & lower
extremityextremity
Origin Origin �� The proximal (towards the center of the body) connective The proximal (towards the center of the body) connective
tissue attachment of the muscle to the bonetissue attachment of the muscle to the bone
Insertion Insertion �� The distal (away from the center of the body) connective The distal (away from the center of the body) connective
tissue attachment to the bone tissue attachment to the bone
Skeletal System contSkeletal System cont’’
Functions (figure 4)Functions (figure 4)�� AgonistAgonist
muscle most directly involved in creating a movementmuscle most directly involved in creating a movement
�� AntagonistAntagonistmuscle that can slow down or stop a movementmuscle that can slow down or stop a movement
�� SynergistSynergistmuscle that assists indirectly in a movement muscle that assists indirectly in a movement
�� StabilizerStabilizermuscle that holds a bone in position so that the muscle that holds a bone in position so that the involved muscles can cause the desired movementinvolved muscles can cause the desired movement
Functional MovementFunctional Movement
TriplanarTriplanar movement (Example)movement (Example)
Muscle functionMuscle function
Lever SystemsLever Systems(figure 5)(figure 5)
Lever Lever �� Rigid object (e.g., bone)Rigid object (e.g., bone)
�� Point of rotation/axis/fulcrum (e.g., joint)Point of rotation/axis/fulcrum (e.g., joint)
ForceForce�� AxisAxis
�� EffortEfforttends to create the desired movementtends to create the desired movement
�� ResistiveResistivetends to oppose the desired movementtends to oppose the desired movement
Lever (Moment) armsLever (Moment) arms�� EffortEffort
perpendicular distance from the pivot to the effort forceperpendicular distance from the pivot to the effort force
�� ResistiveResistivethe perpendicular distance from the pivot to the resistive forcethe perpendicular distance from the pivot to the resistive force
Lever Systems contLever Systems cont’’
Lever classificationLever classification�� First classFirst class
Muscle Force (MF) and Resistance Force (RF) act on Muscle Force (MF) and Resistance Force (RF) act on oppositeopposite sides of sides of fulcrum (figure 6)fulcrum (figure 6)
�� AdvantageAdvantage
�� DisadvantageDisadvantage
�� Second classSecond class
MF and RF act on MF and RF act on samesame side of fulcrum; RF acts at point closer to side of fulcrum; RF acts at point closer to fulcrum than MF (figure 7)fulcrum than MF (figure 7)
�� AdvantageAdvantage
�� DisadvantageDisadvantage
�� Third classThird class
MF and RF act on MF and RF act on samesame side of fulcrum; MF acts at point closer to side of fulcrum; MF acts at point closer to fulcrum than RF (figure 8)fulcrum than RF (figure 8)
�� AdvantageAdvantage
�� DisadvantageDisadvantage
Lever Systems contLever Systems cont’’
Torque (figure A4)Torque (figure A4)
�� Tendency of a force to rotate an object around a fulcrum; Tendency of a force to rotate an object around a fulcrum;
quantitatively force times length of itquantitatively force times length of it’’s moment arm s moment arm
Mechanical advantage (MA)Mechanical advantage (MA)
�� Ratio of the moment arm through which an applied force Ratio of the moment arm through which an applied force
acts to the distance through which a resistance force actsacts to the distance through which a resistance force acts
MA greater/less than oneMA greater/less than one
ExamplesExamples
�� Elbow (Figure 9)Elbow (Figure 9)
�� Knee (Figure 10)Knee (Figure 10)
�� Exercise (Figure 11)Exercise (Figure 11)
StrengthStrength
Contributory FactorsContributory Factors�� Neural Neural
Motor unit recruitment Motor unit recruitment
Motor unit discharge rate Motor unit discharge rate
�� MuscularMuscularLengthLength--tension relationship (Figure 12)tension relationship (Figure 12)
ForceForce--velocity (Figure 13)velocity (Figure 13)
Muscle fiber architecture Muscle fiber architecture
�� Elasticity (Figure 14)Elasticity (Figure 14)
Contractile component (CC)Contractile component (CC)
Series elastic component (SEC)Series elastic component (SEC)
Parallel elastic component (PEC)Parallel elastic component (PEC)
Strength contStrength cont’’
�� Role of stored elastic energy (tendons)Role of stored elastic energy (tendons)
�� Muscle Muscle pennationpennation (Figure 15)(Figure 15)
PennationPennation angle angle
FennationFennation angle and force generating capacity angle and force generating capacity
PannationPannation angle examplesangle examples
Cross sectional area Cross sectional area
Joint angle (Figure 16)Joint angle (Figure 16)
Strength contStrength cont’’
Types of ForcesTypes of Forces�� GravityGravity
Center of gravityCenter of gravity
�� Ground reaction forceGround reaction force
�� TensionTension
�� CompressionCompressionShoulder press, SquatShoulder press, Squat
�� Shear (sideShear (side--toto--side)side)Leg extension, SquatLeg extension, Squat
�� Axial loadingAxial loadingOccurs w/ tensile and compressive forcesOccurs w/ tensile and compressive forces
Important for decreasing the risk of osteoporosisImportant for decreasing the risk of osteoporosis
PowerPower
Defined as force times velocity; rate at Defined as force times velocity; rate at
which work is performedwhich work is performed
ForceForce--velocityvelocity
PowerPower--time (figure 17)time (figure 17)
Rate of force developmentRate of force development
Power contPower cont’’
ApplicationsApplications�� Exercise modeExercise mode
PlyometricsPlyometrics�� Elasticity Elasticity
�� Neural systemNeural system
WeightliftingWeightlifting
Speed training Speed training �� Speed of movement relies upon:Speed of movement relies upon:
power & efficient movement patternspower & efficient movement patterns
�� Requires significant ground forces applied quickly to run fasterRequires significant ground forces applied quickly to run faster
�� Stretch shortening cycle Stretch shortening cycle
�� SpeedSpeed--strengthstrength
�� Application of maximal force at high velocitiesApplication of maximal force at high velocities
�� Types of speed training (technique, sprintTypes of speed training (technique, sprint--assisted & resisted assisted & resisted sprinting)sprinting)
Kinetic Chain TerminologyKinetic Chain Terminology
Closed kinetic chain Closed kinetic chain –– distal end of the distal end of the
““chainchain”” of joints is fixed (figure 18)of joints is fixed (figure 18)
�� MultiMulti--joint doesnjoint doesn’’t equal closed chaint equal closed chain
Open kinetic chain Open kinetic chain –– proximal end of the proximal end of the
““chainchain”” of the joints is fixed (figure 19)of the joints is fixed (figure 19)
Biomechanics and Exercise Biomechanics and Exercise
PrescriptionPrescriptionFree Weight and Exercise PrescriptionFree Weight and Exercise Prescription
Kinetic chainKinetic chain�� Closed chainClosed chain
Increased joint approximation and joint stabilityIncreased joint approximation and joint stability
Not inherently more functionalNot inherently more functional
�� Open chainOpen chainMuscle/joint isolationMuscle/joint isolation
�� ““Specific adaptation to imposed demandsSpecific adaptation to imposed demands”” principle principle (SAID)(SAID)
�� ROMROM
�� Speed of movementSpeed of movement
�� Exercise techniqueExercise technique
Variable Resistance Exercise Variable Resistance Exercise
MachinesMachines
Developed in an attempt to match the muscular Developed in an attempt to match the muscular
torque to the resistance of the exercisetorque to the resistance of the exercise
�� ““CamCam”” varialblevarialble resistance exercise machine concept resistance exercise machine concept
(figure 20)(figure 20)
Variable resistance arm length Variable resistance arm length
Designed to match effort torqueDesigned to match effort torque
�� ““UniversalUniversal”” type exercise machines (figure 21)type exercise machines (figure 21)
Variable effort arm length Variable effort arm length
Decreased mechanical advantageDecreased mechanical advantage
�� ““StriveStrive”” exercise machinesexercise machines
Exercise strength curveExercise strength curve
Variable Resistance Exercise Variable Resistance Exercise
Machines contMachines cont’’
Can exercise machines balance or equate Can exercise machines balance or equate
to the human strength curves?to the human strength curves?
�� Mismatch for most individualsMismatch for most individuals
�� Exercise machines were designed for the Exercise machines were designed for the
““averageaverage”” personperson