Neuromuscular Changes with Aging

Question 1

what age does peak muscle mass and strength occur at

Answer 1

~30 years old

Question 2

what is the percentage of decline in muscle mass and strength regarding aging

Answer 2

muscle mass decline of 3-8% per decade and muscle strength declines up to 15% per decade

Question 3

what age-related skeletal muscle weakness lead to

Answer 3

impaired mobility, decreased walking speed, poor balance, impaired functional performance, and loss of independence

Question 4

what are pathological consequences of age-related skeletal muscle weakness

Answer 4

sarcopenia, dynapenia, and physical frailty

Question 5

age-related decline in muscle function is a result of what

Answer 5

changes in muscle mechanics, changes in neural and neuromuscular function, intrinsic changes within individual muscle fibers, changes to the muscle ultrastructure, and vascular changes

Question 6

what are potential factors contributing to the decline in muscle quality with age

Answer 6

neurological changes and skeletal muscle properties changes

Question 7

what is muscle quality equal to

Answer 7

the ratio of force per unit of muscle size

Question 8

what occurs with the decline in muscle size with age

Answer 8

cross sectional area of whole muscle decreases 3-8% per decade after 30 years and the magnitude of atrophy is muscle-dependent

Question 9

what is a motor unit

Answer 9

one alpha motor neuron and all the muscle fibres it innervates

Question 10

what does one motor neuron innervate

Answer 10

multiple fibres at once via collaterals

Question 11

what is the total force produced during a muscle contraction controlled by

Answer 11

varying the number of motor units recruited and the discharge rate of the action potential that innervates each active motor unit

Question 12

what do motor units undergo through a lifespan

Answer 12

a normal process of remodeling

Question 13

what are age-related neuromuscular factors

Answer 13

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

Question 14

what are the steps of motor unit loss and remodeling

Answer 14

1. motor neurons die with age
2. other motor neuorns grow collaterals to some of the newly orphaned muscle fibers
3. resulting in fewer, larger motor units, fiber-type grouping, and muscle fibers that remain orphaned will atrophy and die

Question 15

what is the estimated rate of motor neuron death with age

Answer 15

1% per year from 30-70 years old than faster rate thereafter

Question 16

what are the consequences of motor unit loss and remodeling

Answer 16

re-innervated muscle fibers adapt to slower nerve supply

Question 17

what does remodeling of the neuromuscular junction lead to

Answer 17

an impaired synaptic transmission

Question 18

what age-related changes occur to muscle fibers

Answer 18

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

Question 19

what percentage of fiber loss occurs from ages 24-50 years old

Answer 19

5% of fast-twitch type 2

Question 20

what percentage of muscle fibre loss occurs from ages 24-50 years old

Answer 20

up to 35%

Question 21

what are intrinsic factors occur from muscle fibres atrophing and exhibiting slower contractile properties

Answer 21

decreased mitochondria function, Myosin ATPase activity Ca2+ handling in the cell, and development of anabolic resistance

Question 22

what is anabolic resistance in aging muscle

Answer 22

the development of anabolic resistance in innervated muscle fibres because of decreased muscle protein synthesis relative to breakdown

Question 23

what occurs with age-related changes in motor performance

Answer 23

decreased muscle strength, decreased maximum power, decreased rate of force development and relaxation, reduced force control, and variable changes in fatigability

Question 24

what are the different assessment modalities for muscle mass

Answer 24

DXA and CT

Question 25

what are the different assessment modalities for muscle strength

Answer 25

grip strength and lower limb muscle strength (isometric)

Question 26

what are the different assessment modalities for physical performance (functional assessment)

Answer 26

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

Question 27

what does physical activity preserve

Answer 27

muscle quality

Question 28

what type of exercise can improve power in older adults

Answer 28

power training