1. Biomechanics of Skeletal Muscle (Ch 6) Objectives n Identify the basic behavioral properties of the musculotendinous unit. n Explain the relationships of fiber types and fiber architecture to muscle function. n Explain how skeletal muscles function to produce coordinated movement of the human body. n Discuss the effects of angle of pull, force- velocity and length-tension relationships n Discuss the concepts of strength, power, and endurance from a biomechanical perspective.

2. Properties, structure and function of muscle n Properties of muscle-tendon function -Extensibility and elasticity Elastic and contractile components (Fig 6.2, p 147) -Irritability and the ability to develop tension n Structural Org of Skeletal Muscle (Fig 6.3 – 6.6) n Motor Unit (Fig 6.7, p 151) n Classification of Muscles -by fiber architecture: parallel, pennate (F 6.11, p 155) -by articulation (number of joints crossed) uniarticulate, biarticulate passive and active insufficiency

6. Biarticular muscle action and synergy

7. Passive insufficiency – due to inability of a multiarticular muscle to allow full ROM at both ends

8. Active Insufficiency – due to inability of a multiarticular muscle to generate force when shortened at one end

9. Electromyography and fiber type recruitment n The motor unit and Electromyography (Figure from lab) -motoneuron& all innervated fibers n Muscle Fiber Types -Slow twitch oxidative (SO), or Type I -Fast twitch oxidative glycolitic (FOG), or Type IIA -Fast twitch glycolitic (FG), or IIB -Functional differences -Fig 6.10, p 152 -Characteristics - Table 6.2, p 153 -Selective recruitment of fiber types – size principle: SO FOG FG

12. Muscle Fiber Types

13. Recruitment proceeds from smallest fibers to largest (the size principle)

14. Factors Influencing Production of Muscular Tension and Applied Force n Force-velocity relationship - Fig 6.17, p 162 n Length - tension relationship - Fig 6.18, p 164 -Elastic and contractile components n Angle of pull - Max turning effect at 90 deg

15. Force- velocity relationship:

18. Active insufficiency: length- tension relationship:

19. Angle of Pull of Muscle & degree of force application Turning component equals Force times sin θ

20. Mechanical Advantage of Elbow Flexors

21. Length of Elbow Flexors as Joint Angle Changes

22. Study Questions For Chapter 6 Biomechanics of Skeletal Muscle n Self-study questions: -What do these terms mean: Strength Endurance Power -Intro probs, p 173, #1,3,8; Add probs, 174 p # 1,2 (My sketch of problem #2 is on next slide) n Homework – due Monday, March 8 -Intro prob, p 173, #9; Add probs, p 174, # 8,9

23. Additional problem #2, p 173: Length-tension, angle of pull combined Sine of