Lecture 34 - Ageing and skeletal muscle

Question 1

What are the multifactorial causes of sarcopenia?

Answer 1

disuse, changing endocrine function, chronic diseases, inflammation, insulin resistance, and nutritional deficiencies

Question 2

What is the criteria for patients to be considering to be exhibiting sarcopenia?

Answer 2

bedridden, can’t independently rise from a chair

gait speed

Question 3

What are the 3 criteria that define sarcopenia?

Answer 3

1. low muscle mass
2. low muscle strength
3. low physical performance

Question 4

Sarcopenia is independent of?

societal factors

Answer 4

ethnicity,
disease states,
income,
health behaviours

Question 5

drop off is greater for activities that require…

Answer 5

force and power

Question 6

typically __ muscles are more affected than ___ muscles

Answer 6

typically fast muscles are more affected than slow muscles

Question 7

What are the factors controlling muscle mass?

Answer 7

Nutritional status
hormones
genetics
innervation
inflammation
oxidative stress
blood flow
exercise (activity)
Disease
protein synthesis/degradation

Question 8

sarcopenia is a neuromuscle syndrome, meaning…

Answer 8

it is concerning Motor units

there is selective de-innervation of the type to MUs

followed by reinnervation with type 1 MUs

Question 9

What causes the selective deinnervation of fast MUs?

Answer 9

Two possibilities:

Loss of signals from nerves to muscles

loss of signals from muscles back to nerves

a difficult hypothesis to test - significant interplay between neural and muscular pathways

Question 10

True of false

with sarcopenia, There is a loss of mosaic pattern of fast and slow fibre distribution

Answer 10

true

fibre type grouping due to selective loss of MUs

Question 11

Before there is wasting of muscle fibres there are other changed, including:

Answer 11

slowing of contraction

changes in SR - impaired release and reuptake of Ca2+

age-related changes in Ca2+ handling affect speed of contraction

contributes to falls and fall-related injuries (can’t quickly retain balance)

Question 12

Summarise the motoneuron changes in aging

Answer 12

a loss of motoneurons with aging and a loss of numbers and diameters of motor axons in the ventral roots

some of these cease functioning (fibres may die)

other send out new axonal branches called sprouts

most susceptible MUs are those for the type IIB fibres and this loss of fast-twitch units, not surprisingly, will prolong contraction time

fast fibres reinnervate less successfully than slow fibers

fast fibres remain deinnervated or they are reinnervated by axonal sprouting from slow fibres.

The loss and atrophy of muscle fibres and the remodelling contribute to overall muscle atrophy

Question 13

possible demyelination could affect NT, slow AP propagation. Other changes to NMJ include:

Answer 13

gradual changes in pre/post synaptic components, incl.

widening of end -plate
longer nerve terminals
fewer side branches

Question 14

There is an increase in ____ in aging muscle making it more stiff

Answer 14

collagen

Question 15

what are the changes in skeletal biomechanica variables with ageing muscle?

Answer 15

decrase max running velocity

decrease stride length

decease stride frequency

increase stride cycle time

increase braking and push off contact time

Question 16

Summarise the cellular and molecular changes that contribute to sarcopenia

muscle fibre
satellite cells
E-c couplng
Adipocyte infiltration
mitochonria
myofilaments
fiber type transformation

Answer 16

muscle fibre
-decrease in number and size (predominately type II)

Satellite cells

• reduced number
• less response to injury

E-c couplng

• disruption/uncoupling
• deficits in Ca2+ release

Adipocyte infiltration
- increase inter and intra muscular adipose tissue

mitochondria

• reduced number
• loss of enzyme content

myofilaments

• reuced single fibre maximal force
• reduction in myosin protein content and function
• reduction in elasticity

fiber type transformation
- fast to slow fibre type shift

Question 17

what happens to sports performance with ageing?

Answer 17

elite status does not protect msucle from gradual losses in fibres/MUs

loss of power a concern for athletes

injuries are more common

most elite athletes begin to show some decine in performance by their 30s

Question 18

what are the problems facing older champions?

Answer 18

diminishing muscle mass

progressive decrease in size of type II fobres

declining VO2 MAX
stiffening connective tissue

Question 19

What can we do to intervene against sarcopenia?

Answer 19

we must attempt to conserve muscle strength for both the prevention and reversal of age-related changes

this can be facilitated by the incorporation of strength training

Question 20

Strength training in the eldery can be effective at adressing…

Answer 20

increase muscle strength, total body mass and muscle fibre area

significant fibre hypertrophy

Question 21

true or false

the strength training adaptations in elderly are likely to result from a combination of neural adaptations and muscle hypertrophy

but we must face the fact that loss of msucle mass is inevitable

Answer 21

true

strength training must be a lifelong commitment if it is to be a preventative measure

Question 22

what are the relevant hormonal changes with ageing

Answer 22

decreased circulating levels of anabolic hormones contribute to changes in muscle size and strength

hormones include: GH, IGF-1, testosterone

compromises efficiency of muscle regeneration as a consequence of daily ‘‘wear and tear’’

Question 23

what are the therapeutic approaches for combating sarcopenia

Answer 23

exercise - strength training

protein supplements

hormonal - GH, testosterone precursors, selective androgen receptor modulators

Question 24

true or false

exercise can slow the rate which the sarcopenia changes occur - therefore exercise is very important

Answer 24

true

but there are practical considerations: is high-intensity strength training suitable for most adults, some maybe not.