Measuring Muscle Strength
- not good for people with functional deficits
- isotonic: constant external resistance; 1 RM, takes a long time
- isokinetic: resistance through whole ROM at constant velocity; isokinetic torque curve, highest point on curve/average distance
- isometric: immovable resistance-MMT and HHD
MMT
- assess muscle strength; essential before prescribing exercises
- formulate treatment
- assess effectiveness of treatment (periodically re-assess)
- indication for assistive devices
- differential diagnosis: patterns of strength deficits
- prognosis
Factors Affecting Strength
- anthropometry: muscle size, cross sectional size, circumference
- fiber type: type 1–>slow twitch and type 2–>fast twitch
- age: both cognitive and chronological (3-4years observation of functional activities)
- gender
- length of lever arms
- pain
MMT Assessment of Strength Dependent Upon
- point of resistance application
- stabilization
- positioning
- motivation and cognition
Proficient in MMT
- knowledge of joint motion
- knowledge of O&I
- ability to palpate muscles or tendons
- ability to distinguish between normal and atrophied contour
- ability to recognize abnormalities of position or movement
MMT Resistance
- direction of pressure is perpendicular to line of pull of muscle
- resistance is applied towards end of GR ROM
- location of resistance applied distally (some exceptions)
- exceptions: pain, pros and cons make sure to document
- midrange is the length of muscle that’s optimal for resistance
MMT Stabilization
- pertinent at proximal joint
- firmness or stability of body is necessary to insure accurate test
- do not stabilize over muscle belly
MMT Positioning
-ability of patient to move against gravity will determine testing position
MMT Palpation
- critical for weak muscles
- helps rule out substitutions
- confirms contraction of desired muscles
MMT Grading
- the higher on the scale (above a 3+) the less reliable the test
- partly due to size differentail
MMT Reliability
- the more standardized all the factors, the more reliable
- accuracy; do the same test on two different occasions and get the same result
- intrarater is more reliable
- highest in grades below 3
- lack of standardized testing procedures resulted in lower intrarater reliability
- interrater reliability improved when all testers used same standardization approach
MMT Valididty
- does test measure what it’s supposed to?
- research says MMT is valid procedure in measuring muscle strength especially for 4 and less
- limited correlations to other assessments in MMT grades above 4/5
- high correlations with MMT grades less than 4/5
MMT Strength
-maximal force a muscle (or group) can generate at a specified or determined velocity
Testing Vs. Screening
- testing: looking at each individual movement and knowing which muscles make that movement; increased time and effort, standardization technique, position specific, gravity specific positions, isolated movements/muscles
- screening: quick overview in position of convenience; difficult to rule out substitutions, weakness should be tested, combines movements in multiple planes, guides you in direction of testing
Vertebral Artery Test
- clearing neck means making sure you’re not blocking this vessel
- supine or sitting
- eyes open
- extend, rotate, side bend
- count backward from 20
- observe
- loss of vision in one or both eyes/double vision/nystagmus
- numbness/tingling hands or feet
- dizziness/vertigo
- slurred speech
- change in mental status
- sudden/severe weakness
- SpPin–>0% (specificity-ability of a test to rule something in)
- SnNout–>67-90% (sensitivity-ability to rule something out)
Elevations-Upper Trap and Levator Scapulae
- options 1 and 2 produce greatest EMG activity in upper trap fibers
- measured as percent max voluntary isometric contraction
Scapular Adduction (Middle Trap)
- lateral rotation of humerus is critical to achieve max activation of middle traps
- EMG show that when tested with this method but with IR EMG activity is reduced
- shoulder must be ER and horizontally abducted to have highest EMG
Scapular Adduction and Depression (Lower Traps)
- highest EMG when muscle is tested as we have been
- also involves significant activity in middle fibers of traps
Scapular Abduction and Upward Rotation (Serratus Anterior)
- low EMG in SA during tests that involve protraction
- highest when SA is tested as it is in book
Shoulder Abduction (Middle Deltoid and Supraspinatus)
- frontal plane
- significantly less EMG in middle and posterior fibers of deltoid during abduction in scapular plane rather than frontal)
- no other studies found that compared EMG activity or force produced in deltoid or supraspinatus during abduction in these two planes
- so testing deltoid and supraspinatus in this plane is appropriate
- some evidence for testing supraspinatus in scapular plane-common clinically (did in class)
- deltoid is key muscle for examining integrity of C5 spinal nerve or neurological segment of spinal cord, complete assessment of this includes strength testing of deltoid and biceps brachii, reflex testing of biceps, and sensory testing of skin over middle deltoid
Shoulder Abduction Scapular Plane (Supraspinatus)
- elevation of arm in scapular plane commonly used
- some controversy
- full can, empty can, and horizontal abduction of shoulder at 100 degrees from prone position with LR (prone full can)
- no statistically significant differences in amount of EMG during these 3 methods
- found decreased EMG in middle delt during empty can test
- concluded that mmt of supraspinatus could best performed with full can
Elbow Flexion (Brachialis and Brachioradialis)
- studies examined relative activation of these two during elbow flexion in varying degrees of forearm rotation show that biceps brachii demonstrates much higher levels of activity when flexing elbow with forearm pronated
- differences in activity between these two muscles due to forearm position much less likely: synergistic elbow flexors regardless of forearm position
- one may decrease activity in biceps brachii muscle by pronating forearm or may increase activity of biceps brachii by supinating forearm
Hip Extension Alternative Test (Glut Max Option 1)
- designed to combine extension and LR in a single test
- glut max is one of most significant LR of hip particularly when hip is in position of less than 45 degrees of flexion
Hip Extension Alternative Test (Glut Max Option 2)
-positioning reflects effort to decrease participation of hamstring muscles in hip extension (flexing knee shortens hamstrings reducing effectiveness as hip extensors)
Neck Flexion
- patients with weak neck flexors may attempt neck flexion with SCM exclusively
- can’t keep chin tucked
- SCM flexes lower cervical spine and also extends head on atlas
Neck Extensors
-much stronger than neck flexors
Facial Weakness
- when examining people for weakness, closely look at muscles of forehead
- lower motor neuron lesions (bell’s palsy) will be unable to raise eyebrow on affected side or close eye tightly on that side
- upper motor neuron lesion (stroke or MS) has no such deficit of forehead movement but eye closure ability is variable
Cranial Nerves
- On, On, On, They Traveled And Found Voldemort Guarding Very Ancient Horcruxes
- Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducent, Facial, Vestibular, Glossopharyngeal, Vagus, Spinal Accessory, Hypoglossal
- function: Some Say Marry Money But My Brother Says Big Brains Matter More
Functions of Cranial Nerves
- smell
- sight
- eye movement
- eye movement
- facial touch/pain; muscles of mastication
- eye movement
- taste; muscles of facial expression
- hearing and balance
- taste; muscles that assist with swallowing
- autonomic functions
- muscles of head movement
- muscle of tongue
Grading for Facial Muscles
- 5 full
- 3 motion performed but with difficulty or only partial ROM
- 1 contraction
- 0 none
Myotonic Stretch Reflex
- mono-synaptic
- afferent-sensory: toward CNS
- efferent: motor
- stimulus: quick stretch (sensory)
- response: muscle contraction
- inhibitory interneuron helps to inhibit antagonist
Guidelines for Reflexes
- encourage relaxation: antagonist contraction limits response, support body part to ensure no muscle contraction occurs, verbal cues, distraction techniques
- proficient use of hammer: loose hold, force and accuracy of tap location, brisk stimulus
- reinforcement techniques: strong muscle contraction away from reflex, must not involve muscle being tested, jendrassik maneuver
Grading Reflexes
- 0: no response-pathology
- 1+: minimal response, slight muscle contraction without joint movement, may need reinforcement-normal if symmetric
- 2+: normal response, mild muscle contraction accompanied by minor joint movement
- 3+: brisk response; moderate to strong muscle contraction with obvious joint movement-normal if symmetric
- 4+: hyperactive reflex, very strong, brisk muscle contraction accompanied by exaggerated joint movement associated with clonus-pathology
Use of HHD and MMT Comparisons
- versatility: clinical settings and research
- don’t like MMT: insensitivity to grades 4 and 5, 25% variation in test grades; detection of small changes with MMT is suspect; different muscles require different percentage of fibers to contract to reach normal grade
Limitations of HHD
- technical: upper limit limitations in some devices
- cost:? relatively inexpensive but still cost over a thousand dollars
- practical: intellectual impairment, hyperactivity, generation of max force inconsistent in some dx: CP, pain, age, must have isometric contraction, isolation of muscle to be tested
Principles of Measurement
- consistency in test position: clinical preference and judgement
- GM whenever possible
- joint position
- max stabilization to ensure reliabilty
- therapist issues: experience, number of trials (average 2-3) intra vs. inter rater (collect data within a clinic)
Force Application
- known location: mark axis and center of force application
- as far away from the axis as possible: magnitude of resistive force applied by therapist decreases as distance from joint center increases
- force perpendicular to segment: must be isometric and to determine true value
- timing: 3-5 seconds force, 10-30 between trials
Calculating Torque
- only meaningful way to compare across subjects
- torque=force x distance
- distance is the perpendicular distance of the force to the joint center
Reliability
- good (acceptable) intratester, lower intertester
- differences affecting interrater: lower values, unacceptable values, effects of experience and sample size, stature, strength
- intersession: acceptable BUT small number of studies, small sample sizes, multiple disease processes and age groups, multiple devices used in the studies make it difficult to determine
Validity
- compared to other types of muscle strength testing does it measure what it’s supposed to?
- vs. isokinetic device: significantly correlated
- vs. MMT low in certain muscles
- predictive: not many studies relating HHD to function
Normative Values
- quadriceps to hamstring reported in adults to children
- nearly 1 in children
- quads are usually stronger than hamstrings in adults
- affected by pathology
Grip Strength
- tense hand as hard as possible for 3-5 second
- wait 30 seconds
- do 2 more trials
- take highest of 3 trials as result
- make sure to be consistent in test position: arm supported on table is most common
Clinical Sensory Testing
- guided by history: what questions asked to determine need to fully assess? Numbness/tingling, isolated motor movements (stumbling, dragging toes), do you do any activities like running, wearing heels every day, etc.
- situations where sensory screening would be appropriate regardless of history: spinal cord injury, neck and back pain, after casting
- comparisons: upper/lower, right/left, proximal/distal on same side-make comparison of where sensory is and where it is not; bilateral is important
- modalities: light touch, pain, proprioception, vibration
- results tell us: absent, impaired, normal
Principles of Sensory Testing
- patient comfort
- clear instructions
- vision occluded during impairment
- initiate exam at area of suspected impairment–>normal region (demarcation: impaired vs. unimpaired, usually distally to proximally)
- compare to standard
- careful documentation
- instrumentation depends on sensory modality being tested
Technique: Pain and Light Touch
- explain procedure: demonstrate on part of body that’s not usually affected by sensory loss
- blinded random order
- American Spinal Injury Association advocates 3 point scale 0=absent 1=impaired 2=normal
- pain: force choice: sharp or dull don’t ask if they feel it, instruct them to let you know as soon as they do.
- light touch: force choice a or b, ask a or b as you do it
Proprioception
- patient supine
- visual demonstration
- blinded during test
- start distal move proximal
- 10 trials
- up, down, neutral, move proximal until they get consistent correct results
Monofilament
- use 10g to start, this is the standard
- big toe, 1st MT, 3rd MT, 5th MT
- press monofilament in until it bends
- have them tell you if they feel it or not
Vibration
- place 128 Hz tuning fork on joints/bony prominences
- will most likely cause pain if there is a fracture
- tell me when you feel the vibration and when it stops
- move distal to proximal
Dermatomes-UE
- look at pictures in notes
- C5: deltoid to mid lateral arm
- C6: lateral forearm to thumb and first finger
- C7: wedge in hand over third finger and palm
- C8: wedge in hand over pinky, fourth finger, and palm
- T1: medial forearm
- T2: upper medial arm
- same areas on back of arm too
Dermatomes-LE
- look at pictures in notes
- L2: anterior upper thighs and posterior middle thighs and back of knees to part of lower posterior middle leg
- L3: anterior knees to mid thighs and posterior medial and inner thighs
- L4: medial lower leg and posterior medial inner leg
- L5: lateral lower leg and dorsum of foot and toes 1-3
- S1: lateral two toes and dorsum of foot and heel and plantar surface of foot
Myotomes
- portion of skeletal muscle that is innervated by single spinal cord level
- screening: bilateral testing against manual resistance
- test all levels grossly and then perform isolated MMT as needed based on screening results
Myotome Levels Upper Quarter
- C5: shoulder abduction, shoulder flexion; deltoid
- C5, C6: elbow flexion; biceps
- C6: wrist extension; extensor carpi radialis longus and brevis
- C7: elbow extension; triceps
- C8: ulnar deviation; flexor carpi ulnaris, extensor CU
- T1: digit abduction/adduction; interossei
Myotome Levels: Lower Quarter
- L2, L3: hip flexion; iliopsoas
- L2, L3, L4: knee extension; quadriceps
- L4: ankle dorsiflexion; anterior tibialis
- L5: extension great toe; extensor hallucis longus
- S1: plantar flexion; gastrocnemius
- S1: ankle eversion; peroneus longus and brevis
Was there a difference between the force generation in GM using the different lever arm for the movements tested?
- there was a difference in force output because a shorter lever arm allows for more force output
- however when you calculate torque and then normalize it it really didn’t make much of a difference in where you applied the resistance, the values were off .06 after normalizing
Was there a difference between GM and GR positions?
- generally GM should generate more torque
- however we found that in the lower limb the opposite was true
- probably due to awkwardness of GM positions in LE and the difficulty in stabilizing
- GR positions had higher force output and torque than GM
Finger Attachment HHD
-helpful in that it allowed for a better area to push on with one digit but the test itself was fairly difficult in positioning of both parties as well as with stabilization: we got pretty inconsistent outputs
What challenges were there in stabilization?
-much smaller and weaker so it was difficult to both stabilize and exert proper force at same time during certain tests