1. Course Content • Introduction to the Course • Biomechanical Concepts Related to Human Movement • Anatomical Concepts Related to Human Movement • Qualitative Analysis of Human Movement

2. Anatomical Concepts Related to Human Movement • The Skeletal System • The Muscular System • The Nervous System

3. The Muscular System • Organ Level Structure & Function • System Level Structure & Function • Injury to the Musculoskeletal System

4. The Muscular System • Organ Level Structure & Function • System Level Structure & Function • Injury to the Skeletal System • Musculoskeletal Function

5. General Structure • ~ 434 muscles • 40%-45% of body weight • 75 pairs of muscles • Organized into compartments • Utilizes 50% of body’s metabolism • Controlled by somatic nervous system

6. General Function • Provides force/torque for movement • Maintenance of upright posture • Body transport • Object manipulation • Aids in venous return • Maintains body temperature

7. Organ Level Structure and Function • Structure of the Muscle Organ • Function of the Muscle Organ

8. Organ Level Structure and Function • Structure of the Muscle Organ • Function of the Muscle Organ

9. Muscle Tissue – Active Component

11. Properties of Skeletal Muscle Tissue • Excitability (Irritability) • Conductivity • Contractility • Extensibility • Elasticity

12. Connective Tissue – Passive Component

13. Nerve Tissue – Passive Component

14. Structure of the Muscle Organ • Muscle organ: 40,000 -1,000,000 fibers • Fascicle: 10-200 fibers • Fiber: 8000 fibrils

15. Muscle Compartments

16. Organ Level Structure and Function • Structure of the Muscle Organ • Function of the Muscle Organ

17. Function of the Muscle Organ Force Production

18. Series & Parallel Elastic Tissue

20. Factors That Affect Force Output • Physiological factors • Cross-sectional area • Fiber type • Neural factors • Muscle fiber activation • Rate of motor unit activation • Biomechanical factors • Muscle architecture • Force-length relationship • Force-velocity relationship

21. Physiological Factors: CSA Training?

22. Physiological Factors: Muscle Fiber Type • Type I • Red, SO, slow-twitch • Type IIa • Red, FOG, fast-twitch, intermediate • Type IIb • White, FG, fast-twitch Training??

23. Percentage of Type I Fibers in Human Skeletal Muscle

24. Factors That Affect Force Output • Physiological factors • Cross-sectional area • Fiber type • Neural factors • Muscle fiber activation • Rate of motor unit activation • Biomechanical factors • Muscle architecture • Force-length relationship • Force-velocity relationship

25. Neurological Factors: Muscle Fiber Activation • All-or-None Principle • Same fiber type within MU • 10-2000 fibers per MU • 120-580 MUs / muscle • MU size influences precision & force of movement

26. Neurological Factors: Muscle Fiber Activation •  # of activated MUs,  force • Training?

27. Neurological Factors: Rate of Motor Unit Activation •  rate of MU activation,  force

28. Single Twitch Multiple Twitch Tetanus Training??

29. Factors That Affect Force Output • Physiological factors • Cross-sectional area • Fiber type • Neural factors • Muscle fiber activation • Rate of motor unit activation • Biomechanical factors • Muscle architecture • Force-length relationship • Force-velocity relationship

30. Nonpennate Muscle Pennate Muscle

31. Ranges of Muscle Pennation in Humans (Yamaguchi et al., 1990)

32. Fiber Density - PCSA

33. Nonpennate Muscle Pennate Muscle

34. CSA & PCSA of Ankle Plantar Flexors (Fukunaga et al., 1992)

35. Biomechanical Factors: Muscle Architecture • Pennate • Greater force (force ~ PCSA) • Non-pennate • Greater range of muscle lengths • Larger ROM • Greater operating range • Shorten at higher velocities • Training?

36. Factors That Affect Force Output • Physiological factors • Cross-sectional area • Fiber type • Neurological factors • Muscle fiber activation • Rate of motor unit activation • Biomechanical factors • Muscle architecture • Force-length relationship • Force-velocity relationship

37. Humans: 2.6-2.8 mm

38. Active Component

39. Passive component

40. Total Force

41. 60% 160% Single Joint Muscles 110-120%

42. Multi Joint Muscles >160% 60%

43. Factors That Affect Force Output • Physiological factors • Cross-sectional area • Fiber type • Neurological factors • Muscle fiber activation • Rate of motor unit activation • Biomechanical factors • Muscle architecture • Force-length relationship • Force-velocity relationship

44. 110-180% isometric Biomechanical Factors: Force-Velocity Relationship Eccentric Concentric Velocity

45. Factors that Affect Force Output • Physiological factors • Cross-sectional area • Fiber type • Neurological factors • Muscle fiber activation • Rate of motor unit activation • Biomechanical factors • Muscle architecture • Length-tension relationship • Force-velocity relationship

46. Summary • Numerous factors affect the force output of the muscle organ. • Identification of these factors allows us to better understand muscle strength and explore alternative training methods that may be effective in increasing muscle strength.