Neuromuscular Changes with Aging Flashcards
what age does peak muscle mass and strength occur at
~30 years old
what is the percentage of decline in muscle mass and strength regarding aging
muscle mass decline of 3-8% per decade and muscle strength declines up to 15% per decade
what age-related skeletal muscle weakness lead to
impaired mobility, decreased walking speed, poor balance, impaired functional performance, and loss of independence
what are pathological consequences of age-related skeletal muscle weakness
sarcopenia, dynapenia, and physical frailty
age-related decline in muscle function is a result of what
changes in muscle mechanics, changes in neural and neuromuscular function, intrinsic changes within individual muscle fibers, changes to the muscle ultrastructure, and vascular changes
what are potential factors contributing to the decline in muscle quality with age
neurological changes and skeletal muscle properties changes
what is muscle quality equal to
the ratio of force per unit of muscle size
what occurs with the decline in muscle size with age
cross sectional area of whole muscle decreases 3-8% per decade after 30 years and the magnitude of atrophy is muscle-dependent
what is a motor unit
one alpha motor neuron and all the muscle fibres it innervates
what does one motor neuron innervate
multiple fibres at once via collaterals
what is the total force produced during a muscle contraction controlled by
varying the number of motor units recruited and the discharge rate of the action potential that innervates each active motor unit
what do motor units undergo through a lifespan
a normal process of remodeling
what are age-related neuromuscular factors
loss and remodeling of motor units, decreased transmission and junctional instability, and atrophy and death of muscle fibres of preferential loss of type 2 muscle fibers
what are the steps of motor unit loss and remodeling
- motor neurons die with age
- other motor neuorns grow collaterals to some of the newly orphaned muscle fibers
- resulting in fewer, larger motor units, fiber-type grouping, and muscle fibers that remain orphaned will atrophy and die
what is the estimated rate of motor neuron death with age
1% per year from 30-70 years old than faster rate thereafter
what are the consequences of motor unit loss and remodeling
re-innervated muscle fibers adapt to slower nerve supply
what does remodeling of the neuromuscular junction lead to
an impaired synaptic transmission
what age-related changes occur to muscle fibers
denervation due to motor neuron death that results in atrophy and dying off of muscle fibers and surviving muscle fibres get smaller in size and exhibit slower contractile properties
what percentage of fiber loss occurs from ages 24-50 years old
5% of fast-twitch type 2
what percentage of muscle fibre loss occurs from ages 24-50 years old
up to 35%
what are intrinsic factors occur from muscle fibres atrophing and exhibiting slower contractile properties
decreased mitochondria function, Myosin ATPase activity Ca2+ handling in the cell, and development of anabolic resistance
what is anabolic resistance in aging muscle
the development of anabolic resistance in innervated muscle fibres because of decreased muscle protein synthesis relative to breakdown
what occurs with age-related changes in motor performance
decreased muscle strength, decreased maximum power, decreased rate of force development and relaxation, reduced force control, and variable changes in fatigability
what are the different assessment modalities for muscle mass
DXA and CT
what are the different assessment modalities for muscle strength
grip strength and lower limb muscle strength (isometric)
what are the different assessment modalities for physical performance (functional assessment)
Short physical performance battery timed UP and GO test, 4 or 6 minute walking speed tests, stair climb test, balance testing, and activities of daily living scales
what does physical activity preserve
muscle quality
what type of exercise can improve power in older adults
power training
