Week 2 - Impairment & measurement of muscle weakness Flashcards
What impairments are managed with exercise?
Strength, endurance, passive ROM, coordination, CR fitness
Weakness/loss of muscle strength results from:
- Decrease in voluntary drive (ability to recruit motor units)
- Decreased muscle cross sectional area/atrophy
Tissues muscle is made up of:
Muscle cells, connective tissue, nerve tissue, blood supply.
Epimysium
Dense, fibrous irregular connective tissue that covers the muscle belly.
Perimysium
Covers the fascicles (bundles of muscle fibres)
Endomysium
Covers muscle fiber (cell)
- Not as tough/resilient
- Wraps over sarcolemma
Motor unit
Single motor neuron + all muscle fibres it innervates
- Power movements > larger unit of muscle fibre vs. fine motor control
Muscle force
Force generated by muscle contraction (or stretch) that tends to shorten muscle
- Rotation/compression/distraction/sheer
Resistive force
Generated by external force + weight of body part
Lever / moment arm
Perpendicular distance betw. the joint centre + the line of force acting on that joint
Torque (moment arm)
Degree to which a force tends to cause rotation about a fulcrum (joint)
Torque equation
force x perpendicular distance (moment arm)
The 3 methods to assessing strength:
MMT, dynamometer, RM testing
Spectrum of weakness - paralysed
No ability to generate force/small flicker of a contraction
Spectrum of weakness - very weak
Movement if gravity is eliminated; can’t move against gravity
Spectrum of weakness - weak
Movement against gravity, but still between normal
Spectrum of weakness - strong
Strength = normal (relative)
MMT grading 0-5
0 - no observable/palp. contraction
1 - Observable/palp. contraction, but no movement
2 - Full ROM not against gravity
3 - Full ROM against gravity
4 - Full ROM against gravity & some manual resistance
5 - Full ROM w/ manual assistance
Factors important for optimising reliability for a range of strength measures:
- Torque
- Perpendicular distance: distance from point of application of force to centre of rotation.
Reliability:
The consistency of measurement, consistency will be improved where variable are held constant.
What can increase reliability?
(1) Point of application of force (perpendicular to limb/close or further away)
(2) Joint angle (changes length of muscle, changes length of moment arm sometimes)
(3) Joint angular velocity: speed of muscle shortening affects ability to generate torque
Validity
Evidence that a test measures what it is supposed to.
