muscle response to inactivity and immobilisation in neurology Flashcards
muscle
Muscle is a dynamic tissue
It responds to demands placed upon it Length (extensibility)
Size (number of muscle fibres)
Force-producing capability (strength and power)
If a muscle’s neurological connection is impaired or altered, the muscle’s performance and eventually its structure will be affected → contracture: loss of range due to soft tissue changes within a muscle
contractures
incidence is unknown in Ireland contracture occurnace brain injury 11-84% stroke 45%-100% MS <50 % muscles undergo fibrosis causing pain and loss of function and independence
clinical factors are hard to determine who will develop a contracture
time is wide for development
may not develop contracture initially but then do.
ability to get knee into full extension is critical
knee contracture - can’t extend
becomes contracture if you can’t achieve a functional posture
summary of muscle fibre
muscle fibres myofibrils filaments striations from overlapping actin and myosin. individual sarcomere
muscle contraction
cross bridges between actin and myosin
z lines are brought closer together
normal - contraction relaxing happens regularly
neuro input is lost
muscle structure changes
thixotrophy
Substances that can be changed from a gel-like substance to a solution after being stirred (Vattanasilp et al 2000)
Muscle has thixotrophic properties
Stiffness depends on history of movement
if muscle moves regularly it is less stiff
neuro impairment
muscle doesn’t move
even if neurology impairment improves muscle will be more stiff
reduced movement and
abnormal neuronal activity
example
gastrocnemius
acute injury to CNS
stroke or relapse in MS
damage to CNS –> paresis affecting gastric
muscle not contracting if resting in bed. + resting in shortened position
muscle rearranges and leads to contracture
paresis from initial loss of neural input
spasticity / spastic dystonia spastic co contraction loss of selectivity weakness and tone abnormalities contracture can cause pain
possible consequences UL
adducted / IR shoulder flexed wrist pronated forearm flexed elbow clenched fist thumb in palm deformity
possible consequences LL
equinovarus striatal toe stiff knee flexed knee adducted thighs - cerebral palsy children
changes in joint
articular structure incrementally responsible for limitation of ROM
myogenic restriction proportionally decreased: very little at 32 weeks
cartilage thickness in decreased in immobilised knee joints but not in those who were immobilised and exercised
muscle atrophy
decrease in whole muscle CSA
loss of muscle mass
72 hours for quadratus lum borum
species dependent length of time immobilised Position of joint during immobilisation Fibre composition of muscle: slow postural muscles atrophy to a greater extent Previous level of activity of muscle
muscle immobilised or inactive in a shortened position
structural changes more likely to occur when muscle is immobilised in a shortened position
loss of sarcomeres up to 40%
breakdown of proteins by catabolic enzymes
CT changes : increase in hydroxyproline and collagen
cross-sectional area
Length tension curve shifts to left
shortened muscle: recovery
Shortened muscle can recover original length if:
It adopts a lengthened position
AND / OR
Normal activity resumes
muscle immobilised in a lengthened position
↑ number of in-series sarcomeres
↑ length of the muscle fibre
↑ length of the tendon
Preservation of the normal length–tension relationship and MTU stiffness
Prevention of accumulation of connective tissue within the muscle
Reduction in muscle atrophy
clinical implications
Muscle is prone to change
Muscle tightness can develop to a greater degree and more rapidly in the presence of neurological hyperactivity (spasticity / rigidity)
Change in length leads to change in strength
Anticipate and prevent the consequences of muscle inactivity
