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