Strength, Weakness & Loss of Dexterity Flashcards
What are the 2 factors that contribute to strength?
- Neural: Activation of motor units
- Muscular: Cross-sectional area of muscle fibres
What are the implications of a loss of strength?
- Contributes significantly to activity limitation
- Leg strength highly correlated with walking speed in the aged
- Strongly correlated with function
- Makes an independent contribution to function after stroke
What evidence is there for the contribution of strength & dexterity to function after stroke?
- Examined relative contribution of strength & dexterity to function for 6 months after stroke
- Strength & dexterity combined predict 75-80% of the variance of function in the first 6/12 after stroke
- Strength makes a significant contribution to function after stroke
- Loss of strength is a more significant contributor than loss of dexterity to physical disability after stroke
What is the evidence regarding leg strength in stroke patients?
- Leg strength measured in people >1 year post stroke
- Compared with age-matched controls
- Strength of people with stroke 1/3-2/3 of normal
- No difference between flexors/extensors or distal/proximal muscles
- Unaffected side also weaker than control
What is the evidence regarding weakness and contracture in stroke patients?
- Measured contracture & strength every 20 deg through full elbow range
- Stroke subjects had more weakness in shortened range
- Contracture did not contribute to inner range weakness
What is the evidence regarding peak force in stroke patients?
- Examined time required to reach peak force after onset of muscle contraction in patients post stroke
- Stroke patients were slow to reach peak force & were unable to generate max force
What is the evidence regarding torque production in stroke patients?
- Compared torque produced during rapid contraction between healthy subjects, MS patients & patients with other UMNLs
- Greater reduction in torque production associated with an increase in contraction speed
What is the evidence regarding force in MS patients?
- Examined force produced over a 30s contraction in MS patients
- Rapid initial reduction in force in MS patients
- MS patients less able to maintain max force over time
What is the evidence regarding the functioning of motor units in stroke patients?
- Functional denervation of motor units occurs from 3/12 post stroke
- By 6/12 post stroke there is only 50% of motor units functioning
What are the characteristics of loss of strength in neurological populations?
- Selective weakness in the shortened range
- Increased time to peak force production
- Greater reduction in force production with increased contraction speed
- Decreased ability to sustain contractions
- Substantial reduction in the number of functional motor units over time
What are the implications of the loss of strength characteristics?
- Routinely assess/train strength
- Assess/train all muscle groups for strength loss
- Assess/train the intact side for strength loss
- Start training early
- Include inner range
- Included sustained & rapid contractions
What is the evidence for strength training in stroke patients?
- Systematic review of strength training in acute & chronic stroke
- Strengthening interventions increase strength, improve function & don’t exacerbate spasticity in stroke patients
- Strength training should routinely include FES, EMG & PRE
What needs to be considered to clinically implement strength training?
- Mode
- Intensity
- Frequency
- Progression
- Monitoring
- Precautions
What does the mode of strength training depend on?
- Level of weakness
- Other impairments
- Neural vs muscular components of strength
- Relationship of weakness to function
- Distribution of weakness
What are the mode options for below grade 2 (Oxford)?
- Mental practice
- Eliminate gravity & friction
- Reduce lever arm
- EMG
- Functional electrical stimulation
What are the mode options for grade 3 & above (Oxford)?
- Add resistance (theraband)
- Perform single & multiple muscle group strengthening
- Consider weight bearing & NWB
What does the intensity of strength training depend on?
Is weakness due to
- Loss of activation of motor units
- Loss of cross sectional area of a muscle fibre
What intensity is recommended when weakness is due to a loss of activation of motor units?
Grade 3 or above:
- 8-12 reps 60-80% 1RM
- Progress when patient can do 12 reps with good form
- Patient must be able to do 8 reps with good form at new intensity
Below grade 3:
- High reps, daily, 5x20 reps
- High mental effort
What intensity is recommended when weakness is due to a loss of cross sectional area of a muscle fibre?
- High physical effort
- High load, low reps
- 60-80% 1RM, 1-3 sets 8-12 reps
What is the recommended frequency of strength training?
- Inversely related to intensity
- Minimum of 1 set
- At least 1 min rest between sets
- 3 times/week
How should strength training be progressed?
- Must include progression to ensure it remains fatiguing
- Either reps, sets, load, number of sessions/week or type (inner/outer, isometric holds etc)
- Only one component should be progressed at a time
What does the monitoring of strength training include?
- Subjective & objective monitoring strategies
- E.g. Borg RPE, fatigue, muscle soreness, dynamometry, MMT, 10RM
- Always monitor function
What are the precautions for strength training?
- Warm-up
- Controlled speed
- Avoid breath holds
- Use good technique
- Monitor
- Progress gradually
What does evidence show regarding spasticity?
- Spasticity is not the main impairment post stroke
- Strength training doesn’t exacerbate spasticity
What does evidence show regarding overwork weakness?
More likely to be fatigue than irreversible loss of strength
What is dexterity?
- Ability to solve any motor task precisely, quickly, rationally & deftly with flexibility in regard to the changing environment
- Loss of dexterity is the loss of coordination of voluntary muscles to meet environmental demands
What are the signs of loss of dexterity?
- Dysmetria: Overshooting (hypermetria) or under shooting (hypometria)
- Dyssynergia: Decomposition of movement
- Dysdiadochokinesia: Inability to perform rapid alternating movements
- Postural instability: Poor balance
What are some of the common adaptive motor behaviours?
- Restriction of amplitude of movement
- Restriction of degrees of freedom
- Excessive pre-shapoing & use of support surface during upper limb tasks
- Excessive BOS, stepping & use of arms during standing & walking
- Increased speed & difficulty slowing down in walking
- Increased variability of performance
What did Kautz & Brown 1998 find regarding loss of dexterity?
- Examined difference in timing of muscle activation between stroke patients & health controls performing ergometer pedalling
- Patients had disordered timing of hamstrings & quads
- Associated with reduced mechanical output
How is dexterity assessed?
- Finger-nose/finger-finger
- Heel-shin
- Toe tapping/heel tapping/supination-pronation
- Heel over shin
- Task performance (adaptive strategies, changing speed/direction, stop on command, add dual task)
What should interventions for improving dexterity include?
- Activity training incorporating all relevant joints
- Not related to assessment tests
What are the types of dexterity activity training?
- Modified (e.g. treadmill)
- Whole task
- Whole task under varying conditions
What are the principles for training dexterity?
- Increase accuracy
- Vary distance
- Vary speed
- Change BOS
- Vary direction
- Vary characteristics of the task
- Vary characteristics of the environment
- Promote flexibility
What are the clinical implications of research regarding dexterity training?
- Loss of dexterity can impair work output & can be present in absence of weakness
- Training must involve whole task practice, multiple joints & postural adjustments
- Function is not possible without strength, but dexterity is also important
- Functional training must be task specific
What evidence is there for upper limb strength training in stroke survivors with mild-mod motor impairment?
- Systematic review of strength training for upper limb in stroke population
- Strength training significantly improves strength & function in the upper limb
- Strength training doesn’t increase spasticity or pain
What evidence is there for reaching ability in stroke survivors with normal strength?
- Assessed stroke patients with normal strength in reaching for a target
- Patients had indirect trajectories & poor inter-joint coordination compared with unaffected side (dyssynergia)
What evidence is there for using reaching training to improve sitting balance in stroke survivors?
- Sitting balance trained in stroke patients using reaching beyond arms length
- Increased reaching distance & speed, increased loading of affected leg
- No improvement in walking/standing balance
What evidence is there for training STS & step-ups in TBI patients?
- TBI patients trained in STS & step-ups
- Significant improvement in STS
