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Kinesiology Andrew L. McDonough, PT, EdD Dominican College

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Presentation on theme: "Kinesiology Andrew L. McDonough, PT, EdD Dominican College"— Presentation transcript:

1 Kinesiology Andrew L. McDonough, PT, EdD Dominican College
Physical Therapy Program

2 “Kinesiology” Functional anatomy (traditional) Biomechanics Statics
Dynamics Kinematics (geometry of motion) Kinetics (forces that account for motion)

3 Voluntary Movement Factors & Levels of Analysis
(Macro)physiologic Biomechanics Motor control Motor learning

4 Types of Motion Translatory Rotary – constant radius
A B Rotary – constant radius Curvilinear – radius varies

5 Basic Components of a Joint System
Muscle attachments (proximal – distal) Axis of rotation Fixed center Instant center Innervation

6 Terms Agonist – Antagonist (context-dependent)
Synergist (3 definitions) Primary vs. Secondary (Tertiary) movers Fixators/stabilizers – Immobilizers

7 Muscle Factors Physiological cross-section Geometry of muscle/tendon

8 Physiological Cross-Section
Less force More force

9 Geometry Type types Fusiform (cigar-shaped) Penniform (feather-shaped)
Bi-pennate Uni-pennate Multi-pennate Bi- Uni- Multi-

10 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

11 Significance of Geometry
Penniform Implies an angle-of-insertion Gross muscle level Muscle fiber level . angle-of-insertion

12 . . Angle-of-insertion T = f x d resultant force X axis rotary
component (“Y”) force . 900 (joint) compressive component (“X”) T = f x d

13 Muscle Contraction Types
Isometric Isotonic Concentric (shortening contraction) Eccentric (lengthening “contraction”) Isokinetic (?)

14 Muscle Contraction Levels of Analysis
Sarcomere (microanatomical) Gross muscle

15 Isometric Contraction
Sarcomere shortens delivering force to tendon Gross length remains constant Demo

16 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

17 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

18 Sources of Tension Muscle (“contractile element”)
Tendon (“non-contractile element” = CT)

19 Premise: Concentric vs. Eccentric Contractions
“Per comparable volumes of muscle tissue, more tension will always be realized during eccentric contractions.”

20 Analysis Concentric contraction Eccentric contraction
Source of tension Contractile elements (muscle) Eccentric contraction Non-contractile elements (CT = tendon) The tendon is in a pre-loaded condition due to previous concentric contraction

21 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

22 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

23 Muscle Contraction & Fiber Types
Concentric: Type I and IIa motor units most active Eccentric: Type IIb motor units most active

24 Relationship Between a Muscle (or Muscle Fiber) & Tension Production
Blix experiments probe dynamometer frog soleus muscle fiber

25 Muscle Lengthened Passively
Tension production will soon become linear and muscle fiber will react elastically Passive Tension Curve Tension Length

26 Muscle Stimulated at Various Pre-set Lengths
Shortening Lengthening 60 Blix Curve or “Length-tension Curve” Tension 100% Rest length Length

27 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

28 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

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

30 Muscle Types One-joint Two (two-or-more)-joint

31 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

32 Two-Joint Muscles General 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

33 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

34 Velocity – Tension Relationship
Eccentric Concentric “Inverse Relationship” Tension - + 100 Demo Velocity

35 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

36 Other Terms Arthrokinematics – study of the relationship between (among) articulating bony surfaces Joint play Congruency Component motion Overall motion


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