muscle strength, length and power Flashcards
what four outcomes does myogenic or muscular system assessment cover?
- muscle bulk/ girth
- muscle length
- muscle power
- muscle strength
what is muscle bulk? how is it measured?
- muscle building; indicative of strength
- measured using tape measure
- compare to healthy limb
what does muscle bulk result in?
- swelling of limb
what are the problems of measuring muscle bulk?
- subjective measure
- intramuscular fat
what is muscle length ?
- ability of a muscle crossing a joint/ joints to lengthen
what muscles are more likely to be injured and why?
- tight muscles
- can lead to muscle imbalance and altered biomechanics
what factors does muscle length also calculate?
- force and tension
what is muscle strength?
- maximal force a muscle or muscle group can generate at a specific or determined velocity
what does muscle strength provide?
- provides stability and mobility for functional movement within MSK system
what is leg muscle power?
- ability to exert force with lower extremities quickly
- lower leg power is an early indicator of poor function
what is power ?
- combination of strength and speed
what does power relate to? - give some examples
- relates to functional assessment
- chair rise
- return to play
- single leg jump
- leg press
what are the limitations of subjective assessments?
- visual, observation of contours e.g., thigh, upper arm
- measuring limb girth with tape measure
- underestimates muscle loss, quadriceps cross sectional area by 22-33%
- little differentiation of anatomical structures : muscle, bone, subcutaneous fat, perimuscular fascia
what are the four objective assessments of muscle function?
- dynamometer (grip strength test)
- force platforms (dynamic strength)
- peak force, leg power, jump height
- sensitivity, normative data to compare
what are the four psychometric properties?
- reliability
- validity
- consistency
- sensitivity
what is reliability ?
- different clinician should be able to use the same tool on the same patient to receive the same outcome
what is validity?
- measurement should test what it’s meant to be testing e.g., dynamometer measures strength
what is consistency?
- same results all the time
what is sensitivity?
- if there’s a change to function/ outcome can the measurement highlight this
what are the four physiological considerations for strength?
- muscle fibre types
- neural factors
- connective tissue integrity
- age
what factors of muscle fibre types influence strength?
- fast/ slow
- regeneration of ATP
- response to training
what neural factors influence strength?
- tension developing capacity
- motor unit recruitment
- firing frequency of motor units
what connective tissue integrity factors influence strength?
- brain signals
how does age influence strength?
- muscle mass
- fibres
- functional motor units
- CSA
- power
what other factors determine strength?
- morphological and neural factors
what are the seven morphological and neural factors of strength?
- contractions
- muscle architecture; pennation angle, echogenicity
- CSA
- mechanical properties e.g., stiffness of structure
- motor unit recruitment, rate coding and motor unit synchronisation
- neuromuscular inhibition
- speed of contraction
what is strength influenced by?
- pathologies (neurological deficits)
- physical activity
what is strength impaired by?
- injury
- infection
- major surgery
- medical conditions
- muscle control
what is strength predictive of?
- quality of life
- mortality
- hospital length stay
- hospital readmission
what are the 10 correlates of strength?
- age
- sex
- muscle fat ratio
- muscle size
- CSA
- pennation angle
- mechanical properties: tone, elasticity, stiffness
- PA
- co- morbidity
- medication
what are the four associations between disease and muscle function?
- osteoarthritis
- diabetes mellitus
- cardiovascular disease
- association with lower leg power compared to age - matched older adults
what is resistance training effective for?
- improving body fat mass
- muscle strength
- performance
what is isometric contraction?
- static
- variable resistance
- no change in muscle length
- no movement
what is isotonic contraction? what are the two types?
- uniform tension
- change in muscle length
- eccentric and concentric
what is eccentric contraction? - give an example
- muscle lengthens with movement
e.g., elbow extension
what is concentric contraction? - give an example
- muscle shortens with movement
e.g., elbow flexion
what should the techniques be? what does it determine?
- techniques safe, simple, reliable, consistent, valid and reproducible
- determines loss in muscle strength
what should you consider and what does this influence?
- consider factors that influence muscle strength
- good understanding influences clinical reasoning skills
- consider positioning> key to visualise muscle
are objective assessments effective?
- no ;
low reliability and validity
is dynamometry effective?
+ less subjective
+ quantifiable outcome
+ sensitivity to change
- not available
is the MCR scale effective?
+ quick
+ simple grading scale
+ good inter-rater reliability
- subjective
what factors affect strength and length outcomes? (10)
- pain
- fatigue
- ROM
- mechanical properties
- emotions; mental health
- occupation
- hobbies
- age and maternity
- handedness
- physical activity levels
what does manual muscle testing determine?
- extent and degree of muscle weakness from disease, injury or disuse
what is the MRC scale?
- modified medical research council
how would you apply manual muscle testing?
- plan therapy
- evaluate function and strength of muscle/ muscle groups
- consider action, individual muscles or group of muscles
what are other testing scales?
- Kendall muscle testing scale
- Daniels and worthingmans manual muscle testing scale
how many grades are in the oxford grading scale?
5
describe 0-5 of the oxford grading scale
0= no contraction
1= flicker/ trace of contraction (limited ROM)
2= muscle activation with gravity minimised
3= muscle activation against gravity
4= muscle activation against some/ minimal resistance
5= muscle activation against examiner’s full resistance
what are the limitations of the oxford grading scale?
- non- linearity: difference between grades 3 and 4 isn’t necessarily the same as diff of 4 and 5
- patient’s variability over time e.g., due to fatigue
- inter- rater reliability
- only assesses muscles when contracting concentrically
- difficulty of applying scale to all patients
- strength rarely assessed as many patients do not possess full range due to respective pathology
what has been made to overcome the oxford rating scale limitations?
- modified versions of oxford scale
- tests inner, middle and outer range
what are the common pathologies?
- stroke
- cerebral palsy
- spinal cord injury
- multiple sclerosis
- Parkinson’s disease
- arthritis
- metabolic syndromes
- muscular dystrophy
- motor neuron disease
- COPD
- heart failure
what are the cautions ?
- unhealed fracture
- dislocation or unstable joint
- situations where active ROM are contraindicated e.g., post operative protocols
- if pain limits participation
- severe inflammation
- severe osteoporosis
- haemophilia
- cognitive concerns/ decreased ability to complete test
what are the contradictions?
- abdominal surgery or hernia
- bony ankylosis
- haematoma
- cardiovascular disease
- pulmonary disease
- prolonged immobilisation
- cases where fatigue may be harmful or exacerbate persons conditions e.g., COPD, MS
