Module 5 Flashcards
What is anabolic resistance?
A diminished capacity of muscles to respond to growth stimuli like protein intake and exercise
This leads to smaller muscle mass and atrophy in older adults.
What type of muscle fibers are preferentially lost with age?
Type 2 (fast-twitch) muscle fibers
These fibers are crucial for generating force and power.
What happens to muscle composition in older adults?
Increased percentage of type 1 (slow-twitch) fibers
This results from the loss of type 2 fibers.
What is the effect of increased fibrotic tissue and fat infiltration in older muscle?
Decreased overall muscle quality and less force production for a given muscle size
The extracellular matrix becomes less effective at transmitting force.
What happens to the number of motor units as individuals age?
Decline in the number of motor units
The largest motor units, which innervate type 2 fibers, are particularly susceptible to death.
What occurs to the size of remaining motor units with aging?
The size of remaining motor units tends to be larger
Surviving motor neurons reinnervate orphaned muscle fibers.
How do neuromuscular junctions change with age?
They become less stable
This can lead to denervation of muscle fibers.
What is the trend in total fiber number and size with aging?
Decreased total fiber number and size
The average size of remaining fibers also decreases.
What is a key problem with muscle activation in older adults?
Worsened ability to activate motor units
This includes difficulty in turning on specific motor units and achieving a high enough firing rate.
What is impaired in muscle fibers of older adults?
Calcium handling
This leads to less calcium release and decreased sensitivity, resulting in less force production.
What is the trend in the rate of force development with aging?
Slower rate of force development and impaired relaxation
Older individuals take longer to turn muscles on and develop force.
True or False: Older adults are more fatigue-resistant during dynamic contractions.
False
They tend to be more fatiguable during dynamic contractions, especially high-velocity ones.
What is observed regarding force steadiness in older adults?
Decreased force steadiness
Force output tends to fluctuate more compared to younger individuals.
What happens to maximum velocity contractions with age?
Decline in maximum velocity contractions
This indicates a reduced ability to perform high-speed movements.
What is the trend in muscle quality as individuals age?
Lower muscle quality (force per area)
This indicates a decline in the amount of force produced per unit area of muscle.
What is the effect of aging on muscle hypertrophy?
Resistance to hypertrophy
Older adults can still increase strength but have a blunted capacity for muscle size increase.
What happens to muscle power as individuals age?
Loss of power
The ability to generate muscle power declines with age.
What is mitochondrial dysfunction associated with aging?
Fewer mitochondria, impaired turnover, damage to mitochondrial DNA, and reduced ATP production
This directly impacts aerobic exercise capacity.
What cardiovascular changes are associated with aging?
Age-related cardiovascular changes and altered lung function
These changes contribute to a decline in aerobic fitness.
Which mechanisms contribute to sarcopenia?
- anbolic resistance
- mitochondria dysfunction
- senescence
in module 4, satellite cells and angiogenesis were also proposed to impact hypertrophy; particularly for older adults
What is anabolic resistance?
Diminished capacity of skeletal muscle in older adults to respond to anabolic stimuli with increased muscle protein synthesis (MPS)
stimuli include: lifting and protein feeding
How does the muscle protein synthesis (MPS) response differ in older adults compared to younger individuals?
The increase in MPS following protein ingestion or resistance exercise is smaller in older adults
This blunted response leads to gradual muscle mass loss over time.
What role does the mTOR pathway play in muscle protein synthesis?
The mTOR pathway is crucial for MPS, and its activation is less in older adults following feeding and exercise
This includes less phosphorylation of mTOR and its downstream targets.
What is meant by reduced translational capacity and efficiency in muscle cells?
The ability of muscle cells to produce new proteins decreases with age
This occurs even when anabolic signals are present.
