1 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Tarrant County College District Massage Therapy Program South Campus Slides from Joe Muscolino, Kinesiology

2 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Describe how a muscle can have a partial contraction, and explain the meaning of the Henneman size principle.  Explain the difference between the intrinsic strength of a muscle and the extrinsic strength of a muscle.

3 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Describe the various types of muscle fiber architecture, and explain the advantages/disadvantages of longitudinal versus pennate muscles.  Describe active tension and passive tension of a muscle.

4 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Hierarchy of motor unit recruitment: Weak contraction = small motor unit Stronger = increasingly large motor units in addition to smaller motor units  Hierarchy known as the Henneman size principle

5 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  If every motor unit of a muscle contracts, the muscle contracts at 100% of its strength.  If only some motor units contract, the muscle will have a partial contraction.

6 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Longitudinal muscles: fibers run longitudinally  Categories of longitudinal muscle Fusiform (spindle) Strap Rectangular Rhomboidal Triangular (fan-shaped) Sphincter

7 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-1 From Muscolino JE: The muscular system manual: the skeletal muscles of the human body, ed 3, St Louis, 2010, Mosby

8 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-1 From Muscolino JE: The muscular system manual: the skeletal muscles of the human body, ed 3, St Louis, 2010, Mosby

9 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Pennate muscles: fibers arranged in a featherlike manner  Types of pennate muscle Unipennate muscle Bipennate muscle Multipennate muscle

10 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-2 From Muscolino JE: The muscular system manual: the skeletal muscles of the human body, ed 3, St Louis, 2010, Mosby

11 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Longitudinal muscles: long muscle fibers  Pennate muscles: short muscle fibers But pennate muscles have more muscle fibers  Fibers of longitudinal muscles oriented along length of muscle  Fibers of pennate muscles oriented at oblique angles to the length of the muscle

12 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Active tension: generated by sliding filament mechanism (i.e., its contraction)  Passive tension: created by fascia of the muscle  Total tension: active and passive tension combined

13 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Explain the relationship between the sliding filament mechanism and shortened active insufficiency and lengthened active insufficiency.  Give an example of shortened active insufficiency and lengthened active insufficiency.  Interpret the length-tension relationship curve for active tension, passive tension, and total tension of a muscle.

14 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Explain the meaning of the active, passive, and total tension curves of the length-tension relationship curve.  Describe the relationship between the concepts of the sliding filament mechanism, active length-tension relationship curve, and active insufficiency.  Define the terms internal force and external force and give an example of each.

15 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Explain the relationship between leverage and the extrinsic strength of a muscle.  Describe the advantage and disadvantage of a muscle with greater leverage.

16 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Active insufficiency: a muscle is weak because of a decrease in the number of myosin-actin cross-bridges during the sliding filament mechanism Can be “shortened” or “lengthened”

17 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Shortened active insufficiency –Occurs when a muscle is shorter than its resting length Lengthened active insufficiency –Occurs when a muscle is longer than its resting length

18 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-3

19 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-3

20 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-4 (Courtesy Joseph E. Muscolino).

21 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-4 (Courtesy Joseph E. Muscolino).

22 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Length-tension relationship curve: Compares length of a sarcomere with the percentage of maximal contraction that the sarcomere can generate

23 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-5

24 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Lessened active tension when muscle is shortened = shortened active insufficiency  When muscle is lengthened = lengthened active insufficiency

25 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-6 Modified from Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, ed 2, St Louis, 2010, Mosby.

26 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Leverage: the mechanical advantage that a force can have when moving an object

27 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Internal forces: generated internally, from within the body  External forces: created externally, outside the body Gravity is the most common

28 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Lever: a rigid bar that can move  Movement occurs at axis of motion  Distance from axis to point of application of force = lever arm Sometimes referred to as a moment arm or effort arm

29 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  The longer the lever arm, the less effort it takes to move the lever.  Mechanical advantage: the advantage of being able to move heavy objects with less effort.  I believe it was Archimedes, an Early Greek “natural philosopher “ (read scientist) who said “Give me a long enough lever and I could move the earth.”

30 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-7Figure 14-8

31 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Bones = levers  Muscles create forces to move bones  Joints = axes of motion Figure 14-9

32 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Explain why a muscle with an attachment that has less than an optimal angle of pull loses extrinsic strength.  Explain how to determine the lever arm of a muscle.  List the three classes of levers and give a mechanical object and muscular example of each one.

33 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Define the resistance force to a muscle’s contraction and give two examples of a resistance force.  You might do this to see if you can: Sketch a region of the body where a muscle is contracting, and draw in the arrows that represent the force of the muscle contraction and the resistance force that opposes the muscle contraction.

34 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Angle of pull must be considered  Optimal angle of pull: As a rule, optimal angle is perpendicular to the long axis of its bone. If angle is oblique, not all the force will go toward moving the bone.

35 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-10

36 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-11

37 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Musculoskeletal lever arm = shortest distance from the center of the joint to the line of the pull of the muscle

38 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-12

39 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  First-, second-, and third-class  The difference is the relative location of the application of force to cause movement (F) and the force of resistance to movement (R) relative to the axis of motion (A).

40 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-13

41 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  First-class levers: F and R on opposite sides of A Figure 14-14

42 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Second-class levers: F and R on same side of A (and F is farther from A) Figure 14-15

43 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Third-class levers: F and R on same side of A (and R is farther from A) Figure 14-16

44 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Muscles often at mechanical disadvantage when working against a force with greater leverage  This is the resistance force.

45 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Figure 14-6

46 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.