1. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 3 Muscular Considerations for Movement

2. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Characteristics of Muscle Irritability –Ability to respond to stimulation Contractility –Ability to shorten when it receives sufficient stimulation –Unique to muscle tissue Extensibility –Ability to stretch/lengthen beyond resting length –Protective mechanism Elasticity –Ability to return to resting length after being stretched –Protective mechanism

3. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Functions of Muscle Produce movement Maintain postures and positions Stabilize joints Other functions –Support and protect visceral organs –Alter and control cavity pressure –Maintain body temperature –Control entrances/exits to the body

4. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Groups of Muscles Muscles typically act in unison, not individually Fascia –Sheet of fibrous tissue –Compartmentalizes groups of muscles

5. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Groups of Muscles (cont.)

6. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Architecture Parallel –Flat, fusiform, strap, radiate (convergent) circular Pennate –Unipennate, bipennate, multipennate

7. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Fiber Organization Fusiform –Parallel fibers and fascicles –High speed of contract, force production –ACS = PCS Anatomical cross section (ACS) Physiological cross section (PCS) –Sartorius, biceps brachii, brachialis

8. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Fiber Organization (cont.) Penniform –3 types Unipennate Off one side of tendon Semimembranosus Bipennate Off both sides of tendon Gastrocnemius Multipennate Both varieties Deltoid –PCS > ACS

9. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins

10. Fiber Type Type I –Slow twitch, oxidative –Red (because of high myoglobin content) –Endurance athletes Type IIa –Intermediate fast twitch, oxidative-glycolytic Type IIb –Fast twitch, glycolytic –White –Sprinters, jumpers

11. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Individual Muscle Organization Belly –Thick central portion Epimysium –Outside covering of a muscle Fascicles –Bundles of muscle fibers Perimysium –Dense connective sheath covering a fascicle Fibers –Cells of a skeletal muscle

12. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Individual Muscle Organization (cont.)

13. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Individual Muscle Organization (cont.)

14. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Individual Muscle Organization (cont.) Endomysium –Very fine sheath covering individual fibers Sarcolemma –Thin plasma membrane branching into muscle Myofibrils –Rod-like strands of contractile filaments –Many sarcomeres in series Sarcoplasma –Cytoplasm of muscle cell Sarcoplasmic reticulum –Specialized endoplasmic reticulum of muscle cells

15. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Individual Muscle Organization (cont.) T-tubules –Extension of sarcolemma that protrudes into muscle cell –Also called, transverse tubule Myosin –Thick, dark filament Actin –Thin, light filament Sarcomere –Unit of myosin and actin –Contractile unit of muscle

16. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Motor Unit Group of muscles innervated by the same motor neuron From 4 to 2,000 muscle fibers per motor unit Action potential –Signal to contract from motor neuron Neuromuscular junction –Also called end plate –Where action potential from neuron meets muscle fiber Conduction velocity –Velocity at which action potential is propagated along membrane

17. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Contraction Resting potential –Voltage across the plasma membrane in a resting state Excitation-Contraction Coupling –Transmission of action potential along sarcolemma Twitch –Rise and fall reaction from a single action potential Tetanus –Sustained muscle contraction from high-frequency stimulation

18. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Twitch and Tetanus

19. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Contraction (cont.) Depolarization –Loss of polarity Repolarization –Movement to the initial resting (polarized) state Hyperpolarization –State before repolarization

20. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Sliding Filament Theory A.F. Huxley Seeks to explain production of tension in muscle Myosin and actin –Create cross-bridges –Slide past one another –Cause the sarcomere to contract

21. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Sliding Filament Theory (cont.)

22. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Attachment 3 ways muscle attaches to bone –Directly –Via a tendon –Via an aponeurosis Tendon –Inelastic bundle of collagen fibers Aponeurosis –Sheath of fibrous tissue Origin –More proximal attachment Insertion –More distal attachment

23. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Attachment (cont.)

24. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Characteristics of a Tendon Transmits muscle force to associated bone Can withstand high tensile loads Viscoelastic stress-strain response Myotendinous junction –Where tendon and muscle join

25. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Mechanical Model of Muscle A.V. Hill Three-Component Model –Contractile (CC) Converts stimulation into force –Parallel elastic (PEC) Allows the muscle to be stretched Associated with fascia surrounding muscle –Series elastic (SEC) Transfers muscle force to bone

26. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Hill Muscle Model

27. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Role of Muscle Origin –Attachment closer to the midline or more proximal Insertion –Attachment further to the midline or more distal

28. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Attachment Sites

29. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Role vs. Angle of Attachment

30. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Role vs. Angle of Attachment (cont.)

31. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Role of Muscle Prime mover –Muscle(s) primarily responsible for a given movement Assistant mover –Other muscles contributing to movement Agonist –Muscle creating same joint movement Antagonist –Muscle opposing joint movement Stabilizer –Holds one segment still so a specific movement in an adjacent segment can occur Neutralizer –Muscle working to eliminate undesired joint movement of another muscle

32. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Net Muscle Actions Isometric –Tension produced without visible change in joint angle Holding arms out to sides Concentric –Muscle visibly shortens while producing tension Up phase of a sit-up Eccentric –Muscle visibly lengthens while producing tension Lowering phase of squat

33. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Actions

34. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins One- and Two-Jointed Muscles Muscles can cross one or two joints One-jointed muscles Brachialis, pectoralis major Two-jointed muscles (biarticulate) –Save energy Gastrocnemius, hamstrings, biceps brachii

35. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins One- and Two-Joint Muscles

36. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Two-Joint Muscles

37. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Factors Influencing Muscle Force Angle of attachment Force-time characteristics –Force increases nonlinearly due to elastic components Length-tension relationship Force-velocity relationship

38. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Force-Velocity Relationship

39. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Force-Length Relationship

40. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Stretch-Shortening Cycle Prestretch –Quick lengthening of a muscle before contraction –Generates greater force than contraction alone –Utilizes elastic component of muscle Prestretch and Fiber Type –Type I Slower prestretch best because of slow cross-bridging –Type II Faster prestretch best because of fast cross-bridging

41. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Plyometrics Conditioning protocol that uses prestretching –Single-leg bounds, depth jumps, stair hopping

42. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Stretch-Shortening Cycle and Plyometric Exercise

43. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Muscle Fatigue Fatigue results from: –Peripheral (muscular) mechanisms –Central (nervous) mechanisms When motor unit fatigues: –Change in frequency content –Change in amplitude of EMG signal Sufficient rest restores initial signal content and amplitude

44. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Strengthening Muscle

45. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Strengthening Muscle (cont.)

46. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Principles of Training Genetic predisposition Training specificity Intensity Rest Volume

47. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Strength Training and the Nonathlete ACSM –2 days per week –8–12 exercises per day Counteracts atrophy of muscle and bone Elderly Children –High intensity not recommended –Epiphyseal plates susceptible to injury under high loads

48. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Training Modalities Isometric –No visible movement –Rehabilitation Isotonic –Same weight throughout range of motion (ROM) Isokinetic –Same velocity, varied resistance Close-linked –Isotonic, in which one segment is fixed in place Variable resistive –Supposedly overloads muscle throughout ROM

49. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Injury to Skeletal Muscle At risk –Two-jointed muscles at greatest risk of strain –Eccentrically contracted to slow limb movement Hamstrings, rotator cuffs –Fatigued or weak muscles –When performing unique task for first time –Already injured Prevention –Warm-up –Build up when starting new program –Recognize signs of fatigue –Give body adequate rest

50. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Summary Characteristics of muscle tissue –Irritability, contractility, extensibility, elasticity Often act in compartmentalized groups Fiber organization –Fusiform, penniform Fiber types –Type I, IIa, IIb Functions of muscles –Produce movement, maintain postures, stabilize joints, and others