Download The Muscular System

Course Content
I. Introduction to the Course
II. Biomechanical Concepts Related to
Human Movement
III. Anatomical Concepts Related to
Human Movement
IV. Qualitative Analysis of Human
Movement
Anatomical Concepts Related to
Human Movement
A. The Skeletal System
B. The Muscular System
C. The Nervous System
The Muscular System
1.
2.
3.
Organ Level Structure & Function
System Level Structure & Function
Injury to the Musculoskeletal System
The Muscular System
I.
II.
III.
IV.
Organ Level Structure & Function
System Level Structure & Function
Injury to the Skeletal System
Musculoskeletal Function
General Structure
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~ 434 muscles
40%-45% of body weight
75 pairs of muscles
Organized into compartments
Utilizes 50% of body’s metabolism
Controlled by somatic nervous system
General Function
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Provides force/torque for movement
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Maintenance of upright posture
Body transport
Object manipulation
Aids in venous return
Maintains body temperature
Organ Level Structure and
Function
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Structure of the Muscle Organ
Function of the Muscle Organ
Organ Level Structure and
Function
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Structure of the Muscle Organ
Function of the Muscle Organ
Muscle Tissue –
Active Component
Properties of Skeletal Muscle
Tissue
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Excitability (Irritability)
Conductivity
Contractility
Extensibility
Elasticity
Connective Tissue –
Passive Component
Nerve Tissue –
Passive Component
Structure of the Muscle Organ
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Muscle organ: 40,000 -1,000,000 fibers
Fascicle:
10-200 fibers
Fiber:
8000 fibrils
Muscle Compartments
Organ Level Structure and
Function
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Structure of the Muscle Organ
Function of the Muscle Organ
Function of the Muscle Organ
Force
Production
Series & Parallel Elastic Tissue
Factors That Affect Force
Output
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Physiological factors
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Neural factors
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Cross-sectional area
Fiber type
Muscle fiber activation
Rate of motor unit activation
Biomechanical factors
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Muscle architecture
Force-length relationship
Force-velocity relationship
Physiological Factors: CSA
Training?
Physiological Factors:
Muscle Fiber Type
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Type I
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Type IIa
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Red, SO, slow-twitch
Red, FOG, fast-twitch, intermediate
Type IIb
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White, FG, fast-twitch
Training??
Percentage of Type I Fibers in
Human Skeletal Muscle
Muscle
%
Muscle
%
Obicularis oculi
Biceps brachii
15 Quadriceps
38-42 First DI
52
57
Triceps brachii
33-50 Abductor pollicis brevis
63
Extensor
digitorum brevis
Vastus lateralis
Gastrocnemius (L)
Diaphragm
Masseter
45
46 Tibialis anterior
49 Adductor pollicis
50 Soleus
60-70
73
80
80
Factors That Affect Force
Output
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Physiological factors
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Neural factors
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Cross-sectional area
Fiber type
Muscle fiber activation
Rate of motor unit activation
Biomechanical factors
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Muscle architecture
Force-length relationship
Force-velocity relationship
Neurological Factors:
Muscle Fiber Activation
All-or-None Principle
Same fiber type within
MU
10-2000 fibers per MU
120-580 MUs / muscle
MU size influences
precision & force of
movement
Neurological Factors:
Muscle Fiber Activation
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 # of
activated MUs,
 force
Training?
Neurological Factors:
Rate of Motor Unit Activation
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 rate of MU
activation, 
force
Single Twitch
Training??
Multiple Twitch
Tetanus
Factors That Affect Force
Output
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Physiological factors
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Neural factors
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Cross-sectional area
Fiber type
Muscle fiber activation
Rate of motor unit activation
Biomechanical factors
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Muscle architecture
Force-length relationship
Force-velocity relationship
Nonpennate Muscle
Pennate Muscle
Ranges of Muscle Pennation in
Humans
(Yamaguchi et al., 1990)
Muscle
Pennation
Angle (deg)
Gluteus maximus
3.4-5.0
Gluteus medius
8.0-19.0
Gluteus minimus
5.0-21.0
Biceps femoris
7.0-17.0
Gastrocnemius (medial)
6.5-25.0
Gastrocnemius (lateral)
8.0-16.0
Fiber Density - PCSA
Nonpennate Muscle
Pennate Muscle
CSA & PCSA of Ankle Plantar Flexors
(Fukunaga et al., 1992)
CSA
(cm2)
PCSA
(cm2)
Medial gastrocnemius
16.49
68.34
Lateral gastrocnemius
11.24
27.78
Soleus
29.97
230.02
Flexor hallucis longus
4.85
19.32
Tibialis posterior
5.40
36.83
Flexor digitorum longus
1.59
9.12
Muscle
Biomechanical Factors: Muscle
Architecture
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Pennate
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Non-pennate
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Greater force (force ~ PCSA)
Greater range of muscle lengths
Larger ROM
Greater operating range
Shorten at higher velocities
Training?
Factors That Affect Force
Output
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Physiological factors
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Neurological factors
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Cross-sectional area
Fiber type
Muscle fiber activation
Rate of motor unit activation
Biomechanical factors
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Muscle architecture
Force-length relationship
Force-velocity relationship
Humans: 2.6-2.8 mm
Active Component
Passive component
Total Force
Single Joint Muscles
60%
110-120%
160%
Multi Joint Muscles
60%
>160%
Factors That Affect Force
Output
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Physiological factors
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Neurological factors
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Cross-sectional area
Fiber type
Muscle fiber activation
Rate of motor unit activation
Biomechanical factors
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Muscle architecture
Force-length relationship
Force-velocity relationship
110-180%
isometric
Biomechanical
Factors:
Force-Velocity
Relationship
Eccentric
Concentric
Velocity
Factors that Affect Force
Output
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Physiological factors
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Neurological factors
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Cross-sectional area
Fiber type
Muscle fiber activation
Rate of motor unit activation
Biomechanical factors
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Muscle architecture
Length-tension relationship
Force-velocity relationship
Summary
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Numerous factors affect the force
output of the muscle organ.
Identification of these factors allows us
to better understand muscle strength
and explore alternative training
methods that may be effective in
increasing muscle strength.