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

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 : (also, see Fig 6.15, p 161) :

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 theta

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 What do these terms mean: -Strength -Endurance -Power n Introductory problems, p 172 -3,8,9 n Additional problems, p 173-4 -1,2,8,9 (My sketch of problem #2 is on next slide)

23. Length-tension, Angle of Pull Combined Sine of