assessment of strength Flashcards
define strength
- ability to generate force to create movement
- capacity to exert force
- ability to do work against resistance
what are 4 causes of muscle weakness?
- lesion of pathology affecting the nerve which innervates the muscle
- any lesion, injury or pathology of the muscle tissue
- disuse of muscle
- immobilisation
compare upper vs lower motor neuron lesion
- upper lesion - lesion in brain or spinal cord
- lower lesion - lesion in peripheral nerves
what are the various effects of immobilisation or disuse on muscle?
- decrease in muscle fibre size
- decrease in size and number of mitochondria
- decrease in total muscle weight
- decrease in protein synthesis
- decrease in muscle tension produced
- atrophy
how do you know if a muscle is weak -ie what would a patient say to you? what might you notice?
- might not be able to do ADL’s everyday
- stiffness - less ROM due to muscle weakness - person cannot actively move the muscle etc
- the use of the word ‘heavy’ - can describe muscle weakness
- unexplained tripping - may point to a weakness in the muscles that produce ground clearance
- intrinsic hand muscles becoming weak - difficulty with handling money or taking keys out of pocket
what are the 4 options to assess strength?
- measuring the cross sectional area - eg tape measure, through CT/ultrasound - not directly measuring muscle strength
- **manual muscle testing **(eg manual or hand on hand resistance ) - eg oxford scale
- **objective measurment **- strain gauge, dynamometry (eg hand grip strength)
- **functional assessment **- eg 1RM
what is the 1 repetition maximum?
max amount of weight you can lift for one repetition on any given exercise
what does the reduction in muscle fibre cross sectional area mean?
- a marker of muscle atrophy
what can CSA be a good predictor of?
mortality in some diseases eg COPD
how is true CSA measured?
using CT or ultrasound
how do we indirectly measure CSA?
- tape measurements of muscle bulk - taken when the muscle is relaxed
- common measurements would be mid thigh, mid calf and upper arm
what is the oxford scale?
a numerical rating scale (from 0-5) that measures the power or strength produced by the contraction of a muscle
what are the 6 different numerical ratings of the oxford scale?
0- no contraction
1- flicker or trace of contraction
2- full AROM with gravity eliminated - ie muscle movement is easier without gravity
3- full AROM against gravity
4- full AROM against gravity and resistance
5- normal
what can hand held dynamometry (HHD) testing used for?
- suitable for assessing strength of people who score 4 or 5 on the oxford scale
- allows measurment of maximum voluntary isometric contraction
what are the limitations of hand held dynamometry?
- requires training
- if the patient is strong, tester may not be able to fully resist the patients effort
- isometric testing ONLY
what are some advantages of using hand grip dynamometry?
- reliable
- easy to use
- useful predictor of physical function in aging adults
- fundamental to ADL’s
what is maximum voluntary isometric contraction (MVIC)?
a standardised method for measuring strength for patients with neurological diseases
what is an isokinetic exercise?
- type of exercise that uses a special machine
- the machine creates diff levels of resistance - that way your movements are at a constant speed, no matter how much force you apply
what are the advantages of isokinetic testing?
- sensitive
- accurate
- tests isometric, concentric and eccentric strength
what are the **disadvantages **of isokinetic testing ?
- expensive
- bulky
- takes a long time to set
- limited to a small number of muscle groups
- limited to open chain kinetic mvt
what is the one repetition maximum?
- the maximal weight that can be lifted once using a proper lifting technique
- gold standard for assessing muscle strength
why would you use 1RM?
- no expensive equipment
- functional and meaningful (ie knowing what weight you can lift can be helpful)
- very reliable
- motivating for the patient
- allows dynamic movement - concentric and eccentric
what are the 2 ways that you can calculate 1RM?
- option 1 - calculate 1RM by determining the maximum weight that a patient can lift without failure of compensatory body movements, with good technique (try to get it in 5 attempts to prevent patient fatigue)
- **option 2 **- calculate the 1RM from a lower weight, using an equation (if u have safety concerns about taking patient to max effort or if you dont have a weight corresponding to the 1RM available
other than the 1RM, what is another method for functional testing of strength?
- performance of a compound movment, such as sit to stand, heel raise, pull up or push up
- reported as either power (speed of performance), absolute repetition number (endurance) and sustained maximal duration (endurance)
what is endurance?
- the ability to undergo prolonged activity
what is muscular endurance?
- the ability of a muscle to sustain an isometric contraction or to continue a dynamic contraction
what is cardiovascular endurance?
- the capacity of the individual to maintain strenous activity of a number of muscle groups or of the whole body for a prolonged period
what is fatigue?
- decrease in max power produced by a muscle, the feeling of discomfort and tiredness and also the increased perception of effort
what is DOMS?
delayed onset muscle soreness
* worse with eccentric exercise
* peak is 24-48 hours post exercise
what is DOMS caused by?
microscopic damage to myofibrils and cytoskeletal framework (endomysium, perimysium and epimysium)
what are the effects of muscle strength training?
- increase in max strength
- increase in endurance
- hypertrophy - increas in muscle mass
- decrease in fatigue
- decrease in soreness and stiffness
