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Muscle

Muscle. Muscle. Most abundant tissue (40-45% of BW). Muscle. Composition endomysium – loose CT surrounding each fiber perimysium – dense CT that bundles multiple fibers into fascicles epimysium – fibrous CT that surrounds entire muscle (fascia). Muscle. Muscle.

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Muscle

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  1. Muscle

  2. Muscle • Most abundant tissue (40-45% of BW)

  3. Muscle Composition • endomysium – loose CT surrounding each fiber • perimysium – dense CT that bundles multiple fibers into fascicles • epimysium – fibrous CT that surrounds entire muscle (fascia)

  4. Muscle

  5. Muscle • Collagen in perimysium / epimysium  tendons • Contraction  forces transported thru CT  tendons (inert)  bones.

  6. Musculotendinous Unit • Tendon - spring-like elastic (very stiff-tight) • In series with muscle (SEC)

  7. Musculotendinous Unit • Epimysium, perimysium, endomysium, and sarcolemma  PEC • parallel w/ contractile component

  8. PEC SEC CC Musculotendinous Unit

  9. Functions of Elastic Components • Ensure readiness for contraction • Ensure contractile elements return to resting position • May prevent overstretching of passive elements

  10. Functions of Elastic Components SEC and PEC are viscoelastic: • absorb energy  to rate of force application • dissipate energy in time dependent manner

  11. Storage of Elastic Energy • SEC can store elastic energy • Return it to system • Plyometrics

  12. Plyometrics • Quick stretch/prestretch loads SEC  counter-movement • Elastic energy is returned to system and movement is carried out

  13. Types of Contraction Eccentric > Isometric > Concentric Eccentric/Isometric • supplemental tension thru SEC • longer contraction times  greater cross-bridge formation

  14. Types of Contraction Isokinetic – constant velocity  accommodating resistance Isotonic – constant tension on muscle throughout ROM

  15. Types of Contraction Isoinertial • constant resistance • int. torque  resistance  isometric • int. torque > resistance  concentric

  16. Types of Contraction Isoinertial • simulate ADL • inertia is overcome • muscle contracts concentrically and torque is submaximal

  17. Force Production Length–tension relationship • Tension/force is greatest when @ resting position

  18. Length-Tension Relationship

  19. Length-Tension Relationship Total Tension Active Tension Tension Passive Tension Resting Length Length

  20. Length-Tension Relationship CC --> Active Tension SEC and PEC --> Passive Tension > length --> greater contribution of elastic component to total tension

  21. Length-Tension Relationship Single joint vs. 2 joint muscles

  22. Length-Tension Relationship Constant muscular tension • Lower metabolic cost for eccentric contractions • Mechanical energy is stored in elastic components

  23. Short-fiber muscle of large cross-section Tension Long-fiber muscle of small cross-section Length Length-Tension Relationship

  24. Isometric Load Eccentric Concentric 0 Velocity Force-Velocity Curve Force

  25. Architecture • Pennation • Fiber Length • PCSA

  26. Pennation FT = FMcos

  27. Fiber Length 40 - 100 mm • sartorius (450 mm) • semitendinosus (160 mm) • soleus (20 mm)

  28. Fiber Length longer fibers • # of sarcomeres •  range of excursion • producer  velocity shorter fibers • greater ability to produce force

  29. PCSA • Linearly related to max force output • Relationship between PCSA and Fiber Length

  30. PCSA and Fiber Length

  31. Effect of Temperature •  in conduction velocity •  in frequency of stimulation  in force production

  32. Effect of Temperature •  in metabolism  efficiency of muscle contraction •  in elasticity of collagen in SEC and PEC  extensibility in musculotendinous unit

  33. Mechanisms of  temperature •  in blood flow thru warming up/exercise •  in metabolism, release of energy from contractions, friction (contractile components

  34. Muscle Injury & Mobilization • Early motion may reduce atrophy • Generation of // fiber orientation • More rapid vascularization • Tensile strength returned more quickly

  35. Muscle Disuse • Selective atrophy of Type I fibers • electrical stimulation may help minimize atrophy

  36. Resistance Training • Hypertrophy vs. hyperplasia • Alteration of fiber type

  37. Resistance Training Basic Concepts: • Apply resistance • Progressive overload • PRE

  38. Stretching • muscle flexibility • maintains/increases joint ROM •  elasticity and length of musculotendinous unit • permits musculotendinous unit to store energy (time and amplitude dependent) in SEC and contractile components

  39. GTO • in series with contractile proteins (extrafusal) – respond to increase in tension  inhibit contract and enhance relaxation

  40. Intrafusal muscle spindles Primary • respond to changes in rate of lengthening • dynamic response • strong

  41. Intrafusal muscle spindles Secondary • respond to the actual length change • static response • weak

  42. Conflicts rate of stretch slow may bypass the dynamic response • negating the spindles

  43. Main Goal inhibit muscle spindle effect and promote Golgi effect  enhance stretch

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