L12 Muscle Aging

Question 1

What is the trend in strength as people age?

Answer 1

At early 50s, strength trend starts to go down

There is a greater decline in strength in legs than arms

There is large loss in muscle cross sectional area in the elderly - muscle fibre number also decreases

Question 2

What happens to motor units as you age?

Answer 2

50% reduction in motor units in elderly compared to young subjects - so some fibres aren’t being controlled therefore they will die.

Fewer alpha motor-neurons in the spinal cord of aged people

Question 3

Describe the changes in human muscle contractile character with increasing age

Answer 3

At early 50s, strength trend goes down.
Greater decline in strength in legs than in arms
marge muscle CSA loss in elderly
50% reduction in motor units in elderly compared to young subjects
Fewer alpha neurons
Fewer but bigger motor units in older people

Question 4

Explain how maximal muscle force may decline in old age

Answer 4

As you get older, you generate less force at the same velocity
Fewer alpha motor neurons in the spinal cord
Many motor units die

Question 5

How does muscle fibre grouping and decreased contractile speed come about in old age?

Answer 5

Grouping –> Motor units die, there is some collateral innervation with nearby fibres - this then makes a new fibre grouping of mixed myosin isoforms

Decreased contractile speed –> lower tetanic fusion frequency

Question 6

What happens to performance as you age?

Answer 6

performance declines with age despite maintenance of physical activity.
- less dramatic decline in performance for more endurance based sport - eg marathon time hold a lot longer than basketball performance

Active people will have about 10 more years of independence when it comes to leg strength. 60 years vs 70 years for the point at which people cant get out of a chair unaided anymore

Question 7

What is the force-velocity relationship with age

Answer 7

As you get older you generate less force at the same velocity

Question 8

What is the twitch time course?

Answer 8

= the resultant force of all motor units activated by a stimulus

If preferential loss/atrophy of one fibre type happens then total twitch time course will not change