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

2. Properties, structure and function of muscle
Properties of muscle-tendon function
Extensibility and elasticity
Elastic and contractile components (Fig 6.2, p 147)
Irritability and the ability to develop tension
Structural Org of Skeletal Muscle (Fig 6.3 – 6.6)
Motor Unit (Fig 6.7, p 151)
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. Passive insufficiency – due to inability of a multiarticular muscle to allow full ROM at both ends

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

8. Electromyography and fiber type recruitment
The motor unit and Electromyography (Figure from lab)
motoneuron & all innervated fibers
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

11. Muscle Fiber Types

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

13. Skeletal Muscle Function
Types of muscle contraction
Concentric (muscle length is decreasing)
Eccentric (muscle length is increasing )
Isometric (muscle length is constant)
Roles assumed by muscles
Agonist (prime and assistant movers)
Antagonist
Stabilizer
Neutralizer
Synergist

14. Biarticular muscle action and synergy

15. Application of force of muscular contraction
Strength
Amount of torque a muscle group can generate at a joint (related to physiological cross-sectional area)
Endurance
Resistance to fatigue
Ability of muscle group to continue to repeat or sustain submaximal torque
Fatigue
Performance decrement
Power
Work rate
Combination of strength and speed

16. Study Questions For Chapter 6 Biomechanics of Skeletal Muscle
Self-study questions:
Intro probs, p 173, #1,3,; Add prob, 174 p # 1