Musculoskeletal ConceptsMusculoskeletal Concepts

Dr. Suzan AyersDr. Suzan AyersWestern Michigan UniversityWestern Michigan University

Lecture OverviewLecture Overview

Bone functions & structureBone functions & structure

Joint classification and functionsJoint classification and functions

Muscle structure & function/contractionsMuscle structure & function/contractions

Synergistic/Antagonistic muscle rolesSynergistic/Antagonistic muscle roles

Components of muscular fitnessComponents of muscular fitness

Bone FunctionsBone Functions

Mechanical functionsMechanical functions– Support for weight bearingSupport for weight bearing– Protect internal organsProtect internal organs– Sites for muscle attachmentSites for muscle attachment

Physiological functionsPhysiological functions– Heal/Maintain integrityHeal/Maintain integrity– Store essential minerals (i.e., calcium, Store essential minerals (i.e., calcium,

phosphate)phosphate)– Immune system (marrow produces blood cells)Immune system (marrow produces blood cells)

Bone StructureBone Structure CompositionComposition

– Calcium and phosphorous Calcium and phosphorous – Collagen: toughness, flexibility (1/3)Collagen: toughness, flexibility (1/3)– Calcium salts: hardness, rigidity (2/3)Calcium salts: hardness, rigidity (2/3)

Bone StructureBone Structure Bone cellsBone cells

– Osteocytes (mature bone cells)Osteocytes (mature bone cells)– Osteoblasts (build bone)Osteoblasts (build bone)– Osteoclasts (remodel bone)Osteoclasts (remodel bone)

Bone types Bone types ((1° difference is1° difference is organizationorganization))– SpongySpongy: irregular latticework; releases Ca : irregular latticework; releases Ca easier, more like a trampolineeasier, more like a trampoline– CompactCompact: concentric ring structure; provides : concentric ring structure; provides

protection/support; more like concreteprotection/support; more like concrete

Factors influencing bone compositionFactors influencing bone composition– Bone shape (femur vs. vertebra)Bone shape (femur vs. vertebra)– Function (skull vs. foot bones)Function (skull vs. foot bones)

Pg. 18-21: Bony Architecture Relative to Pg. 18-21: Bony Architecture Relative to FunctionsFunctions

Joint ClassificationsJoint Classifications

SynovialSynovial– Joint cavity; bones joined by articular capsule Joint cavity; bones joined by articular capsule

and often ligaments; most familiar major and often ligaments; most familiar major joints joints (knee, ankle)(knee, ankle)

Articular cartilageArticular cartilage Joint capsuleJoint capsule Synovial membrane (lubrication, protection, Synovial membrane (lubrication, protection,

nutrition)nutrition) Ligaments Ligaments (major source of joint stability)(major source of joint stability)

– Ball and socket: circular motion (hip, shoulder)Ball and socket: circular motion (hip, shoulder)– Hinge: back & forth motion (ankle, knee, Hinge: back & forth motion (ankle, knee,

elbow)elbow)– Biaxial/Saddle: motion in 2 planes (knuckles)Biaxial/Saddle: motion in 2 planes (knuckles)

Joint FunctionsJoint Functions Movement planesMovement planes

– Sagittal/Longitudinal Sagittal/Longitudinal runrun

(vertical: left/right)(vertical: left/right) Flexion (angle decreases)Flexion (angle decreases) Extension (angle increases)Extension (angle increases)

– Coronal/FrontalCoronal/Frontal jjaxjjax

(vertical: front/back)(vertical: front/back)

– TransverseTransverse swing batswing bat

– (horizontal: top/bottom)(horizontal: top/bottom)

Muscular StructureMuscular Structure Muscles cross bonesMuscles cross bones

Muscle-tendon unitMuscle-tendon unit– bone-tendon-muscle-tendon-bonebone-tendon-muscle-tendon-bone

Relationship between direction of Relationship between direction of muscular pull and joint axis of rotation muscular pull and joint axis of rotation determines resulting joint actiondetermines resulting joint action

Smooth muscle Smooth muscle (digestive system, blood vessels)(digestive system, blood vessels) Cardiac muscleCardiac muscle Skeletal muscle Skeletal muscle (p. 26)(p. 26)

– Cells are elongated w/ many nuclei, ergo fibersCells are elongated w/ many nuclei, ergo fibers– ActinActin(thin)(thin) & myosin & myosin(thick)(thick) create striated create striated

appearanceappearance– Motor unit: a nerve & associated muscle fibersMotor unit: a nerve & associated muscle fibers

5 main properties of muscle5 main properties of muscle– ExcitabilityExcitability from neural stimulation from neural stimulation– ContractilityContractility in response to neural stimulation in response to neural stimulation– Conductivity Conductivity of electrical signals to coordinate of electrical signals to coordinate

motionmotion– Extensibility Extensibility shape distortionshape distortion– Elasticity Elasticity return to original shapereturn to original shape

Muscular Function/ContractionsMuscular Function/Contractions Muscular contraction Muscular contraction (pull only, no push)(pull only, no push)::

– cock-connect-pull-release (cross-bridge cycling)cock-connect-pull-release (cross-bridge cycling)– http://www.sci.sdsu.edu/movies/actin_myosin_gif.html

Calcium essential for muscular contraction Calcium essential for muscular contraction Types of contractionsTypes of contractions

– ConcentricConcentric (shortening): produce movement (shortening): produce movement– EccentricEccentric (lengthening): control movement (lengthening): control movement– IsometricIsometric (same length): maintain (same length): maintain

posture/stabilityposture/stability– IsokineticIsokinetic (same speed) (same speed)– IsotonicIsotonic (same tension) (same tension)

Speed of movement: 2-1-4 Speed of movement: 2-1-4 (conc/ecc relationship)(conc/ecc relationship)

Muscle types relative to joint actionsMuscle types relative to joint actions– Monoarticular (muscle crosses one joint Monoarticular (muscle crosses one joint

brachialisbrachialis))– Biarticular (muscle crosses 2 joints Biarticular (muscle crosses 2 joints hamstringhamstring))– Polyarticular (muscle crosses >2 joints Polyarticular (muscle crosses >2 joints

forearmforearm)) Muscular contraction produces all joint Muscular contraction produces all joint

actions of which it is capableactions of which it is capable Limitations to ROMLimitations to ROM

– Joint capsule tension on stretching side of jointJoint capsule tension on stretching side of joint– Flexibility of associated muscles/tendonsFlexibility of associated muscles/tendons– Soft tissues on compressed side of jointSoft tissues on compressed side of joint– Proximity/Contact of bony parts forming jointProximity/Contact of bony parts forming joint

Synergistic/Antagonistic RolesSynergistic/Antagonistic Roles SynergisticSynergistic

– Contributing to desired motion, often by Contributing to desired motion, often by stabilizationstabilization

AntagonisticAntagonistic– Opposing desired motionOpposing desired motion

Examples of eachExamples of each– Biceps: deltoids (s), triceps (a)Biceps: deltoids (s), triceps (a)– Pectoralis: triceps (s), lats (a)Pectoralis: triceps (s), lats (a)– Quadriceps: gluteals (s), hamstrings (a)Quadriceps: gluteals (s), hamstrings (a)

Role of synergistic/antagonistic muscle Role of synergistic/antagonistic muscle groupsgroups

Need for appropriate training sequenceNeed for appropriate training sequence

Little Ditties About Muscular Little Ditties About Muscular FitnessFitness

Motor unitMotor unit– Motor nerve & all muscle fibers it innervatesMotor nerve & all muscle fibers it innervates

Contractile forceContractile force– Depends on # & size of motor units recruitedDepends on # & size of motor units recruited

Table 4.1 Table 4.1 (Sharkey, p. 46)(Sharkey, p. 46)

– Slow-twitch/-oxidative (SO)Slow-twitch/-oxidative (SO)– Fast-oxidative glycolytic (FOG)Fast-oxidative glycolytic (FOG)– Fast-glycolytic (FG)Fast-glycolytic (FG)– SO recruited first, then FOG then FGSO recruited first, then FOG then FG (size (size

principle)principle)

DOMSDOMS– Micro-tears, edema, inflammation, enzyme Micro-tears, edema, inflammation, enzyme

leakageleakage

Components of Muscular FitnessComponents of Muscular Fitness StrengthStrength

– Max force exerted in 1 effortMax force exerted in 1 effort– Unrelated to fiber typeUnrelated to fiber type– Fiber type differences based on rate of force Fiber type differences based on rate of force

productionproduction PowerPower

– Strength x speedStrength x speed Muscular EnduranceMuscular Endurance

– Ability to sustain sub-maximal contractionsAbility to sustain sub-maximal contractions– Small not large muscle groups (more CV Small not large muscle groups (more CV

endurance)endurance)

Power EndurancePower Endurance– Repeated performance of a skill w/ adequate Repeated performance of a skill w/ adequate

speedspeed

Reaction TimeReaction Time– Time between stimulus & response (processing & Time between stimulus & response (processing &

signaling)signaling)

QuicknessQuickness– How an athlete reacts within a small areaHow an athlete reacts within a small area– Combination of reaction time & speed of Combination of reaction time & speed of

movementmovement– Has learned, trained and genetic componentsHas learned, trained and genetic components

SpeedSpeed– Final product of reaction time & quicknessFinal product of reaction time & quickness

BalanceBalance– Maintenance of equilibrium (dynamic or static)Maintenance of equilibrium (dynamic or static)

FlexibilityFlexibility– ROM through which joints moveROM through which joints move– Influenced by gender, habitual use and Influenced by gender, habitual use and

stretching of joint and associated structuresstretching of joint and associated structures– Sport-specific & inversely related to joint Sport-specific & inversely related to joint

stabilitystability

AgilityAgility– Rapid change of speed & direction while Rapid change of speed & direction while ↔↔

balancebalance