basic biomechanics 5th edition by susan j hall ph d l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Basic Biomechanics , (5th edition) by Susan J. Hall, Ph.D. PowerPoint Presentation
Download Presentation
Basic Biomechanics , (5th edition) by Susan J. Hall, Ph.D.

Loading in 2 Seconds...

play fullscreen
1 / 34

Basic Biomechanics , (5th edition) by Susan J. Hall, Ph.D. - PowerPoint PPT Presentation


  • 485 Views
  • Uploaded on

Basic Biomechanics , (5th edition) by Susan J. Hall, Ph.D. Chapter 6 The Biomechanics of Human Skeletal Muscle. Behavioral Properties of the Musculotendinous Unit. 1) extensibility : ability to be stretched or to increase in length

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

Basic Biomechanics , (5th edition) by Susan J. Hall, Ph.D.


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
basic biomechanics 5th edition by susan j hall ph d
Basic Biomechanics, (5th edition)by Susan J. Hall, Ph.D.

Chapter 6

The Biomechanics of Human Skeletal Muscle

slide2

Behavioral Properties of the Musculotendinous Unit

1) extensibility: ability to be stretched or to increase in length

2) elasticity: ability to return to normal resting length following a stretch

slide3

Behavioral Properties of the Musculotendinous Unit

  • Components of elasticity:
    • parallel elastic component - passive elasticity derived from muscle membranes
    • series elastic component - passive elasticity derived from tendons when a tensed muscle is stretched
slide4

Parallel Elastic Component

Series Elastic Component

Contractile Component

Behavioral Properties of the Musculotendinous Unit

From a mechanical perspective, the musculotendinous unit behaves as a contractile component (muscle fibers) in parallel with one elastic component (muscle membranes) and in series with another elastic component (tendons).

slide5

Behavioral Properties of the Musculotendinous Unit

What is the stretch-shortening cycle?

  • eccentric contraction (in which the muscle is actively stretched) followed immediately by concentric contraction
  • examples?
slide6

Behavioral Properties of the Musculotendinous Unit

3) irritability: ability to respond to a stimulus

4) ability to develop tension: the contractile component of muscle function

slide7

Structural Organization of Skeletal Muscle

What is a muscle fiber?

(single muscle cell surrounded by a membrane called the sarcolemma and containing specialized cytoplasm called sarcoplasm)

slide8

Structural Organization of Skeletal Muscle

What do we know about muscle fibers?

  • some fibers run the entire length of a muscle; others are shorter
  • skeletal muscle fibers grow in both length and diameter from birth through adulthood
  • fiber diameter can be increased through resistance training
slide9

Structural Organization of Skeletal Muscle

What is a motor unit?

  • single motor neuron and all fibers it innervates
  • considered the functional unit of the neuromuscular system
slide10

FT ST

Twitch Tension

Time

Structural Organization of Skeletal Muscle

Fast twitch (FT) fibers both reach peak tension and relax more quickly than slow twitch (ST) fibers. (Peak tension is typically greater for FT than for ST fibers.)

slide11

TYPE IIA

TypeIFast-TwitchTypeIIB

Slow-Twitch Oxidative Fast-Twitch

Oxidative

Glycolytic Glycolytic

CHARACTERISTIC

(SO)

(FOG)

(FG)

Contraction Speed

slow

fast

fast

Fatigue rate

slow

intermediate

fast

Diameter

small

intermediate

large

ATPase concentration

low

high

high

Mitochondrial

high

high

low

concentration

Glycolytic enzyme

low

intermediate

high

concentration

Skeletal Muscle Fiber Characteristics

slide12

Structural Organization of Skeletal Muscle

How are muscle fibers organized?

  • parallel fiber arrangement: fibers are roughly parallel to the longitudinal axis of the muscle; examples are?
  • pennate fiber arrangement: short fibers attach to one or more tendons within the muscle; examples?
slide13

Pennate fiber arrangements

Parallel fiber arrangements

Structural Organization of Skeletal Muscle

slide14

Skeletal Muscle Function

How are motor units (MUs) recruited?

  • slow twitch (ST) fibers are easier to activate than fast twitch (FT) fibers
  • ST fibers are always recruited first
  • increasing speed, force, or duration of movement involves progressive recruitment of MUs with higher and higher activation thresholds
slide15

Skeletal Muscle Function

What terms are used to describe muscle contractions based on change in muscle length?

  • concentric: involving shortening
  • eccentric: involving lengthening
  • isometric: involving no change
slide16

Skeletal Muscle Function

What roles are assumed by muscles?

  • agonist: acts to cause a movement
  • antagonist: acts to slow or stop a movement
  • stabilizer: acts to stabilize a body part against some other force
  • neutralizer: acts to eliminate an unwanted action produced by an agonist
slide17

Skeletal Muscle Function

What are disadvantages associated with muscles that cross more than one joint?

  • active insufficiency: failure to produce force when slack
  • passive insufficiency: restriction of joint range of motion when fully stretched
slide18

Skeletal Muscle Function

active insufficiency: failure to produce force when muscles are slack (decreased ability to form a fist with the wrist in flexion)

slide19

Skeletal Muscle Function

passive insufficiency: restriction of joint range of motion when muscles are fully stretched (decreased ROM for wrist extension with the fingers extended)

slide20

(Low resistance, high contraction velocity)

Force

Velocity

Factors Affecting Muscular Force Generation

The force-velocity relationship for muscle tissue: When resistance (force) is negligible, muscle contracts with maximal velocity.

slide21

isometric maximum

Force

Velocity

Factors Affecting Muscular Force Generation

The force-velocity relationship for muscle tissue: As the load increases, concentric contraction velocity slows to zero at isometric maximum.

slide22

Total Tension

Active Tension

Tension

Passive Tension

50 100 150

Length (% of resting length)

Factors Affecting Muscular Force Generation

The length-tension relationship: Tension present in a stretched muscle is the sum of the active tension provided by the muscle fibers and the passive tension provided by the tendons and membranes.

slide23

Factors Affecting Muscular Force Generation

What is electromechanical delay?

Myoelectric activity

Force

Electromechanical delay

Stimulus

(time between arrival of a neural stimulus and tension development by the muscle)

slide24

Muscular Strength, Power and Endurance

How do we measure muscular strength?

(the amount of torque a muscle group can generate at a joint)

slide25

Ft

Ft

Muscular Strength, Power and Endurance

How do we measure muscular strength?

The component of muscle force that produces torque (Ft) at the joint is directed perpendicular to the attached bone.

slide26

Muscular Strength, Power and Endurance

What factors affect muscular strength?

  • tension-generating capability of the muscle tissue, which is in turn affected by:
    • muscle cross-sectional area
    • training state of muscle
slide27

Muscular Strength, Power and Endurance

What factors affect muscular strength?

  • moment arms of the muscles crossing the joint (mechanical advantage), in turn affected by:
    • distance between muscle attachment to bone and joint center
    • angle of the muscle’s attachment to bone
slide28

Muscular Strength, Power and Endurance

A

B

C

The mechanical advantage of the biceps bracchi is maximum when

the elbow is at approximately 90 degrees (A), because 100% of muscle

force is acting to rotate the radius. As the joint angle increases (B)

or decreases (C) from 90 degrees, the mechanical advantage of

the muscle is lessened because more and more of the force is pulling

the radius toward or away from the elbow rather than contributing

to forearm rotation.

slide29

Muscular Strength, Power and Endurance

What is muscular power?

  • the product of muscular force and the velocity of muscle shortening
  • the rate of torque production at a joint
  • the product of net torque and angular velocity at a joint
slide30

Force-Velocity

Power-Velocity

Force

Power

Velocity

Muscular Strength, Power and Endurance

The general shapes of the force-velocity and power-velocity curves for skeletal muscle.

slide31

Muscular Strength, Power and Endurance

What is muscular endurance?

  • the ability of muscle to exert tension over a period of time
  • the opposite of muscle fatigability
slide32

Muscular Strength, Power and Endurance

What is the effect of muscle temperature (warm up) ?

(the speeds of nerve and muscle functions increase)

slide33

Muscular Strength, Power and Endurance

With warm-up, there is a shift to the right in the force-velocity curve, with higher maximum isometric tension and higher maximum velocity of shortening possible at a given load.

Normal body temperature

Elevated body temperature

Force

Velocity

slide34

Chapter 6

The Biomechanics of Human Skeletal Muscle