LifeSpan Muscle Changes - Lecture 33 Flashcards
How does muscle mass develop through early life, adolescent and older age
Increase significantly in early life and then starts to decrease slightly through adolescent and older age.
Is the change in muscle the same for everyone?
It’s different for those who are active their whole life and those are hardly active.
What are the differences for those who exercise and don’t? (Muscle mass)
Those who exercise peak high and end high but those who don’t exercise won’t peak as high and will end low.
What is the disability threshold?
Point in which we loser functional capacity.
Independence?
Lose independence to do activities we once used to do
How can disability threshold be held off for later in life?
Increase physical activity, occupational therapy, etc.
What is the peak skeletal muscle mass for females?
20kg
Peak skeletal muscle mass for males?
30kg
Peak Height Velocity?
The point in which the muscle growth is the fastest. Earlier in women than men.
Differences in gap of Composite Strength between males and females
Throughout puberty and after puberty men will have a larger gap in strength
What is the trend between females and males in fat free mass?
Females tend to feel a plateau in FFM at around 14 while males experience it at around 17-18
Percentage fat comparison
%BF decreases for males at 17 while for females it starts to increase at 14.
How do males not have an increase in %BF?
Due to the increase in fat free mass (skeletal muscle) it offsets the increase in %BF
What is the muscle mass trend in adult stages?
Men and women both decrease but men are still above in muscle mass.
What age does peak muscle mass occur?
35
What age does peak muscle mass start to deter?
45
What are benefits of muscle strength in children?
Increase motor skills, increase PA participation, enhancing body composition changes and learning new skills
What is the overall affect of muscle strength in children?
Life-long PA Participation and Health
Sarcopenia
The relationship of increasing age and loss of muscle mass.
How does Sarcopenia (the decline) happen more often? Risk factors
Through the presence of chronic disease and sedentary lifestyle.
How do we mitigate the loss of muscle mass?
Slowed by regular PA participation; high intensity resistance training.
In what ways does Sarcopenia affect muscle mass?
Size (atrophy) and fibre number
Sarcopenia of Type 1 and Type 2 through Atrophy
Type 1: 1-25% decrease in cross sectional
Type 2: 25-50% decrease in cross sectional area
Sarcopenia through number of fibres
(percentage loss throughout years)
50-70 yrs (1-2% per year)
70-80yrs (10-25%)
>80 yrs (40%)
Is there a change in muscle fibre type through sarcopenia and aging?
No; aging does not alter overall fibre composition.
Why is Type II likely to be more affected?
This is the functional one that we can easily grow through strength training, but the one we can easily lose through aging.
What are potential mechanisms in which Sarcopenia happens?
Programmed Cell Losses, functional denervation, Metabolism, Nutrition, Hormones
Programmed Cell Losses
Apoptosis (cell death) causes muscle fibres to be lost
Functional Denervation
Motor Unit Recruitment decreases, so signalling to muscle fibres weakens
Metabolic Implications
Rate of protein synthesis decreases as well as ATP production. Protein metabolism increases
Sarcopenic-Obesity
Increase in %BF, decreases skeletal muscle which causes more fat than muscle
Nutrition Implications
Inadequate nutrition causes protein synthesis to shift and not favour muscle production.
Hormonal Implication
Reduction in testosterone reduces anabolic processes, which results in loss of muscle mass. Aging affects the effectiveness of anabolic hormones to target tissues
What age does muscle strength start to peak?
Ages 25-35
What age does muscle strength start to decline?
Around 40-49
What is low muscle strength highly associated with?
Low functional activities
Dose-response pattern of muscle strength
Older adults participate in more frequent and more intense PA increase muscle strength
Dynapenia
Loss of muscle strength not muscle mass
How much loss of Skeletal Muscle Mass explains loss of skeletal muscle strength?
6-10% overall through aging
Where does the remaining 90% go?
Neuromuscular changes to muscle strength. Muscle strength declines much quicker than Muscle Mass
Prevalence of dynapenia in Men
46-87%
Prevalence of Dynapenia in Women
50-82%
