Muscle Weakness (ch5) Flashcards
What type of muscle is under voluntary control?
Skeletal muscle
What is a motor neuron and all the fibers it innervates?
Motor unit
Which type of muscle fibers are large in diameter and suited for quick, explosive actions?
Fast twitch fibers (type 2)
What is a muscle’s capacity to produce force depending on its length of muscle relative to its resting length.
Length tension relationship
At what length can muscle produce the most force?
Normal resting length
Which type of muscle fibers are smaller in diameter and most suitable for long duration low force contractions?
Slow twitch fibers (type 1)
Describe what takes place during a muscle contraction?
Action potential reaches the end of a motor nerve > Stimulates the release of Acetylcholine from nerve terminal > Acetylcholine binds to receptors on muscle fibers spreading the action potential > Results in myosin head binding to actin filaments > Myosin head pulls on actin filaments to cause muscle contraction
What causes a reduction in force production by a muscle that occurs after repeated contractions?
Fatigue
What are the different types of muscle fiber pennation (shapes)?
Longitudinal Radiate Fusiform Unipennate Bipennate Multipennate
How many muscle tear grading categories are there?
Grade 1 to 3
What are the characteristics of a grade 1 tear?
A few muscle fibers are torn
Minor swelling and discomfort, little pain w/ palpation
Little if any discoloration
Muscle can contract w/ normal strength
What are the characteristics of a grade 2 tear?
Partial tear, most common type
Causes moderate pain w/ contraction against resistance and contraction will be weak
Moderate pain w/ passive stretching
Moderate swelling and pain w/ palpation
What are the characteristics of a grade 3 tear?
Complete muscle rupture
Profound weakness
Severe swelling and discoloration, possible palpable gap in muscle belly
What percentage of muscle strains account for all athletic injuries?
50%
What can cause muscle weakness?
Muscle disuse
Myopathy
Neurological muscle conditions
What are neurological diseases that can affect performance?
Cerebral palsy
Myasthenia gravis
Peripheral nerve injury ie carpal tunnel
What causes cerebral palsy?
Non progressive lesion of the developing brain causes a persistent and changing disorder of movement and posture that appears early in life and is often associated w/ muscle weakness
Describe myasthenia gravis?
A disorder that prevent efficients transmission from the nerves to muscles, causes weakness primarily characterized by fatigue
Describe carpal tunnel?
its a peripheral nerve injury that causes weakness of the hand muscles innervated by the median nerve
What are typical musculoskeletal tests and measures?
Anthropometric measurements
ROM
Manual muscle testing
What is the contraction strength and movement of a Grade 3 manual muscle test?
Contraction strength: Fair 50%
Movement: Complete ROM against gravity
What is the contraction strength and movement of a Grade 5 manual muscle test?
Contraction strength: Normal 100%
Movement: Complete ROM against gravity w/ maximal resistance
What is the contraction strength and movement of a Grade 1 manual muscle test?
Contraction strength: trace amounts
Movement: Evidence of slight contractility but no joint motion
What is the contraction strength and movement of a Grade 4 manual muscle test?
Contraction strength: Good 75%
Movement: Complete ROM against gravity w/ some moderate resistance
What is the contraction strength and movement of a Grade 2 manual muscle test?
Contraction strength: Poor 25%
Movement: Complete ROM against gravity ELIMINATED
What is a hand held dynamometer?
A device used to measure force of muscle groups in the hand
What is the fastest and most efficient way to assess muscle strength?
Manual muscle testing