Download Muscle Activity—Anatomic Reverse actions

Brunnstrom’s Clinical Kinesiology Sixth Edition
CHAPTER 4
Muscle Activity and Strength
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Introduction
 Discussion of muscles on a macroscopic level
 Last chapter: physiology of motion
 Present chapter: mechanics of motion
 Presentation of both active and passive
tissue influences on motion
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscle Activity
 Recording muscle activity
 Electromyography
 Electrodes—surface, needle, indwelling
 Record contraction/relaxation patterns
 Record relative amount of muscle activity
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscle Activity
 Muscle activation
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Isometric
Concentric
Eccentric
Isotonic
Isokinetic
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscle Activity—Anatomic
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Muscle actions
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Typical scenario:
1. Proximal attachment is stabilized.
2. Distal attachment moves toward proximal.
3. Distal segment moves against gravity.
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Open (OKC) vs. Closed Kinetic Chain
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OKC
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Distal segment free to move
Uninfluenced by other segments or joints
Non-weight-bearing
CKC
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Distal segment fixed
Proximal and distal segments affected
Weight-bearing
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscle Activity—Anatomic
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Reverse actions
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Muscles sometimes have “reverse” actions:
1. Proximal attachments move toward distal
attachments (closed kinematic chain [CKC]).
1.
Such as flexion of the thigh at the knee while sitting down.
2. Eccentric actions are typical in reverse actions that go
with gravity.
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscle Activity—Functional
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Agonist
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Antagonist
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Synergist
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscle Strength
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Muscle size
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Cross-sectional area (CSA)
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Larger CSA—greater force-generating capability
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Hypertrophy
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Atrophy
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscle Strength
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Fiber architecture
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Fusiform
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Fascicles long and parallel
Example: Sartorius
Greater range of motion and speed capability
Pennate (uni-, bi-, or multi-)
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Attach at oblique angles to a common tendon
Greater force-producing capability
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscle Strength
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Length
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Resting length
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Crossbridge activity as a function of length
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Length-tension relationship
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscle Strength
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Moment arm
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100% of muscle force rotates joint when
insertion is perpendicular to bone segment
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Example: elbow at 90°, biceps insertion
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Angle of insertion influences torque
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscle Strength
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Active tension
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Number of motor units
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Type of muscle fibers (motor units) recruited
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Rate (frequency) of firing of motor units
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscle Strength
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Age and gender
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Increase in strength from birth to adolescence;
peak between 20 and 30 years of age
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Males generally stronger than females
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Insufficiencies
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Applies only to multi-articulate muscles:
Passive insufficiency
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Can’t be stretched to full ROM at all joints
simultaneously
Active insufficiency
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Can’t contract to full ROM at all joints
simultaneously
Copyright © 2012 F.A. Davis Company