Muscle Atrophy and Muscle Function

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Questions and Answers

What is the primary consequence of muscle atrophy due to disuse?

Loss of passive tension

Diminished capacity of muscle for developing torque (correct)

Postural abnormality

Reduction in muscle bulk

What is the characteristic of muscle atrophy due to neurogenic causes?

Only occurs in lower limbs

Takes weeks or months to develop

Develops rapidly within 2-3 weeks (correct)

Only occurs in upper limbs

What is the purpose of examining muscle bulk during a physical examination?

To visually inspect muscle shape and symmetry (correct)

To determine muscle endurance

To assess muscle strength

To evaluate muscle power

What is the effect of stroke on motor units in affected extremities?

50% decrease in motor units within 2 months Signup and view all the answers

Which type of muscle fibers are more affected in stroke patients?

Fast twitch fibers Signup and view all the answers

What is the pattern of strength loss in stroke patients?

Greater loss in distal extremities than proximal Signup and view all the answers

What type of synergistic patterns can be produced by lesions of the corticospinal tracts, such as stroke?

Obligatory synergies Signup and view all the answers

What is the primary purpose of activity-based task analysis?

To understand and evaluate the demands of a task and the performance demonstrated Signup and view all the answers

What is the term for the process of moving from a supine to a sitting position in bed?

Supine-to-sit Signup and view all the answers

What is the term for a prolonged decrease in absolute strength and endurance due to over-activity?

Overwork weakness Signup and view all the answers

What is the term for the scale used to assess perceived exertion during physical activity?

Borg Scale of Perceived Exertion Signup and view all the answers

What is the term for functionally linked muscles that are constrained by the CNS to act cooperatively to produce an intended motor action?

Synergies Signup and view all the answers

What is the term for the process of breaking down a specific activity into its component parts to understand and evaluate the demands of the task?

Activity-based task analysis Signup and view all the answers

What is the primary outcome of stimulating stretch-sensitive IA afferents of the neuromuscular spindle?

Muscle contraction Signup and view all the answers

What is the term for the ability to perform daily living skills, such as feeding, dressing, and grooming?

ADLs Signup and view all the answers

What is the purpose of positioning the muscle in mid-range during deep tendon reflex testing?

To ensure adequate muscle contraction Signup and view all the answers

Which of the following is a characteristic of a hypertonic muscle?

Increased muscle contraction Signup and view all the answers

What is the primary function of the Jendrassik maneuver?

To evaluate reflex integrity Signup and view all the answers

What is the Waternberg pendulum test used to assess?

Quadriceps or hamstrings spasticity Signup and view all the answers

What is the Modified Ashworth scale used to estimate?

Spasticity Signup and view all the answers

Study Notes

Muscle Atrophy

Disuse atrophy develops after weeks or months of inactivity
Neurogenic atrophy occurs rapidly (2-3 weeks) after a lower motor neuron (LMN) lesion
Consequences of muscle atrophy include:
- Diminished capacity of muscle for developing torque
- Reduced passive tension
- Loss of joint stability
- Postural abnormality

Examination of Muscle Bulk

Visually inspect muscle shape and symmetry
Compare size and contour
Measure limb girth
Palpation at rest

Strength and Power

In stroke patients, there is a 50% decrease in motor units of affected extremities within 2 months
Greater loss of fast twitch fibers
Impairments in grip strength
Strength loss is greater in distal extremity than proximal
Strength losses are also found in normal extremities

Examination of Strength

Manual Muscle Testing (MMT)
Use active vs passive restraint
Identify substitutions
Use hand-held dynamometers
Use isokinetic dynamometers
Electromyography (EMG)

Endurance

Fatigue is a common symptom in neurological conditions such as post-polio syndrome, MS, stroke, ALS, and Duchenne muscular dystrophy
Exhaustion limited endurance
Overwork weakness: prolonged decrease in absolute strength and endurance due to over-activity
Delayed-onset muscle soreness (DOMS)

Examination of Fatigue

Identify fatigue threshold
Use Fatigue Impact Scale (FIS)
Use Modified Fatigue Impact Scale (MFIS)
Use Fatigue Assessment Scale
Use Borg Scale of Perceived Exertion

Voluntary Movement Patterns

Synergies are functionally linked muscles that act cooperatively to produce an intended motor action
Abnormal synergistic patterns can occur in lesions of the corticospinal tracts (e.g., stroke)

Activity-Based Task Analysis

Break down a specific activity into its component parts to understand and evaluate the demands of the task and the performance demonstrated
Identify activity demands and environmental demands

Taxonomy of Tasks

ADLs (Basic)
IADLs
Functional mobility skills
BADLs
IADLs
Functional Mobility Skills (FMS)

Passive Motion Testing

Normal
Hypertonic
Hypotonic
Slow velocity vs High velocity
First stretch response
Successive stretch response
Clonus
Clasp knife response
Symmetry

Modified Ashworth Scale

Most frequently used clinical method for estimation of spasticity

Special Tests

Pendulum test
EMG
Myotonometry

Wartenberg Pendulum Test

Patient is seated or lying with lower leg hanging over the end of the couch
Examiner extends the leg to the horizontal position, while the patient is told to relax
Leg is then released and allowed to swing freely under the action of gravity

Reflex Integrity

Deep Tendon reflexes
Superficial Cutaneous reflexes
DTR (Deep Tendon Reflex) results from stimulation of stretch-sensitive IA afferents of the neuromuscular spindle producing muscle contraction
Muscle positioned in mid-range for adequate response
Increased in UMNL (e.g., stroke)
Decreased in LMNL (e.g., peripheral neuropathy)

Jendrassik Maneuver

Enhances reflexes by distracting the patient

Primitive and Tonic Reflexes

Present during infancy
Not recognizable in adults in pure form

Cranial Nerve Integrity

Assess cranial nerve function

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Description

This quiz covers muscle atrophy, its types, and consequences, including disuse and neurogenic atrophy, and their effects on muscle function, strength, and endurance.