KinesiologyKinesiologyAndrew L. McDonough, PT, EdD

Dominican College

Physical Therapy Program

“Kinesiology”

• Functional anatomy (traditional)

• Biomechanics– Statics– Dynamics

• Kinematics (geometry of motion)• Kinetics (forces that account for motion)

Voluntary Movement Factors& Levels of Analysis

• (Macro)physiologic

• Biomechanics

• Motor control– Motor learning

Types of Motion

• TranslatoryA B

• Rotary – constant radius

• Curvilinear – radius varies

Basic Components of aJoint System

• Muscle attachments (proximal – distal)

• Axis of rotation– Fixed center– Instant center

• Innervation

Terms

• Agonist – Antagonist (context-dependent)

• Synergist (3 definitions)

• Primary vs. Secondary (Tertiary) movers

• Fixators/stabilizers – Immobilizers

Muscle Factors

• Physiological cross-section

• Geometry of muscle/tendon

Physiological Cross-Section

Less force More force

Geometry

• Type types– Fusiform (cigar-shaped)– Penniform (feather-shaped)

• Bi-pennate• Uni-pennate• Multi-pennate

Bi- Uni- Multi-

Significance of Geometry

• Fusiform– Parallel arrangement of fibers (all have same

proximal and distal attachments)• Virtually ALL (less ~10%) of force delivered to

attachments– Have large force (torque) generating potential– Muscles/fibers to be impulsive but not endurant

Significance of Geometry

• Penniform– Implies an angle-of-insertion

• Gross muscle level• Muscle fiber level

angle-of-insertion .

Angle-of-insertion

angle-of-insertion .

. (joint) compressivecomponent (“X”)

resultant force

rotarycomponent (“Y”) force

T = f x d

Xaxis

900

Muscle Contraction Types

• Isometric

• Isotonic– Concentric (shortening contraction)– Eccentric (lengthening “contraction”)

• Isokinetic (?)

Muscle ContractionLevels of Analysis

• Sarcomere (microanatomical)

• Gross muscle

Isometric Contraction

• Sarcomere shortens delivering force to tendon

• Gross length remains constant

Demo

Concentric Contraction

• Sarcomere shortens

• Gross muscle shortens pulling on bony attachments– If the muscle crosses a joint – the joints

moves through a ROM via torque created

Demo

Eccentric “Contraction”

• A “lengthening reaction”

• Occurs in a muscle that has already undergone a concentric contraction– External force applied exceeds internal

muscular force being generated• Muscle lengthens under neuro-motor control

Sources of Tension

• Muscle (“contractile element”)

• Tendon (“non-contractile element” = CT)

Premise: Concentric vs. Eccentric Contractions

• “Per comparable volumes of muscle tissue, more tension will always be realized during eccentric contractions.”

Analysis

• Concentric contraction– Source of tension

• Contractile elements (muscle)

• Eccentric contraction– Source of tension

• Contractile elements (muscle)• Non-contractile elements (CT = tendon)

– The tendon is in a pre-loaded condition due to previous concentric contraction

EMG Activity

• Ratio: 0.5 : 1.0 (eccentric : concentric)– Tension realized is the sum-total of contractile

& non-contractile elements– Muscle working eccentrically will not have to

“work as hard” since some the total tension is provided by the pre-loaded tendon

Metabolic Activity

• Consequently if the muscle is not working as hard under eccentric control less energy is required to sustain a contraction by a factor of 10 – 30%– Less lactic acid is produced eccentrically

Muscle Contraction & Fiber Types

• Concentric: Type I and IIa motor units most active

• Eccentric: Type IIb motor units most active

Relationship Between a Muscle (or Muscle Fiber) & Tension

Production

• Blix experiments probe

frog soleus muscle fiberdynamometer

Muscle Lengthened Passively

• Tension production will soon become linear and muscle fiber will react elastically

Tension

Length

Passive Tension Curve

Muscle Stimulated at VariousPre-set Lengths

Tension

Length

Rest length

Shortening Lengthening

Blix Curve or“Length-tension Curve”

0 100%

60

Length-Tension Relationship

• “During active contraction a muscle (or muscle fiber) will generate maximal tension at or slightly greater than rest length.”– Levels of analysis

• Gross muscle• Muscle fiber/sarcomere

Demo

Motor Control System

• Constantly evaluates tension via length assessment (GTOs & spindles)– Often optimizes tension via maintaining

muscle length

• Usually “goes out of its way” to maintain length

Question

What happens when a muscle is called upon to do the job it is intended to do (i.e., shorten)?

Muscle Types

• One-joint

• Two (two-or-more)-joint

Active Insufficiency

• Two-joint muscle shortens simultaneously over both joints– Rapidly loses length (shifts left on the length-

tension curve)• Force and torque production decrease quickly

Two-Joint MusclesGeneral Rule

• In a motor control context, two-muscles rarely contract over both (all) joints simultaneously– While one end of the muscle is shortening

over its associated joint– The other end is being lengthened over its

associated joint– The net effect: preserve length and therefore

force and torque

• Motor control system avoids active insufficiency in most cases

Passive Insufficiency

• Muscle passively elongated over both (all) joint simultaneously– At some point the muscle reaches its elastic

limit • ROM will be limited across both joints

Velocity – Tension Relationship

Tension

Velocity0 100

ConcentricEccentric

- +

“Inverse Relationship”

Demo

Other Terms

• Strength – ability to generate tension

• Power – rate of doing work (T=f x d)– Low power– High power

• Endurance – ability to sustain the work being preformed

Other Terms

• Arthrokinematics – study of the relationship between (among) articulating bony surfaces– Joint play

• Congruency

– Component motion– Overall motion