Muscle aging - Week 4 Flashcards
At what ages do our muscle strength decline?
Begins at age 40
Becomes more rapid at age 70
What gender is more effected my muscle strength loss ?
Men
Which part of the body suffers more muscle strength loss and possible reason ?
Lower body loses 40%
Compared to upper body at 33% decrease
Can be due to increase in sitting as we get older so arms and hands would be used more
What is the equation for power?
Power = force x velocity
What is important for function and why?
Rate of force production
Helps prevent falls
What happens to our limbs due to loss of muscle mass when we get older? (2)
Increase in subcutaneous fat
Increase in inter muscular fat - makes harder for muscular contraction
From the age of 40 what percent of muscle is lost till 70?
8% per decade
0.5-1% per annum
From the age of 70 what percentage of fat is lost ?
Up to 15% per decade
Which gender has a steeper regression in body mass over time ?
Men
Which type of muscle fibres are more effected by atrophy?
Type 2 muscles are more affected compared to type 1
Is more mass lost or more strength lost with atrophy ?
More strength is lost
Can still have muscle mass but strength decreases
What does loss of muscle fibres cause?
Decrease in force production
decrease/slower muscle contraction
What is a possible reason for fat accumulation with age ?
Decrease in exercise so muscle is lost and fat increases as fat isn’t used as a fuel source
What happens to motor units with age
/
Less motor units
Leads to less muscle activation
What does the loss of motor units lead to ? (3)
Muscle fibres become denervated
Causes muscle atrophy and fibre loss
Less force can be produced as a result
What happens to type 2 muscle fibres as we age (4) ?
Type 2 become denervated from type 2 MU
Type 1 MU branch out and innervate type 2 fibres
Type 2 fibres then develop type 1 characteristics
Less type 2 fibres as a result of age
What happens to motor units as a result of type 2 muscle fibre denervation?
Motor units become bigger
All fibres would be activated at once which makes it harder to do fine motor skills
Decrease in motor unit efficiency
What happens to fibre type grouping and sharp change with age?
Type 1 fibres become more clustered together due to increase in type 1 MU
Type 2 fibres get squashed and misshapen , become less efficient
Leads to increased fat accumulation in muscles
In terms of fatigue what happens with muscles with age?
Due to increase in type 1 fibres, muscular fatigue resistance increases
Overall how does denervation alter muscle characteristics ?
Increased co-expression of myosin isoforms
Decreased force output
Decreased velocity of contraction and power
Overall how does reinnervation alter muscle characteristics ? (2)
Increased size of MUs - less efficient
Some preservation in muscle mass
What changes occur for excitation-coupling process ?
Decrease in Ca+ release from SR
Changes to SR function , decrease Ca+ uptake
Slowing of myosin molecule, decreases speed of shortening/contraction
Reduced acto-myosin cross bridges, decreases force output
How does being an athlete with lots of muscle compared to an untrained person differ with age ??
Athlete has more muscle mass reduction
Athlete still ends up with more muscle than untrained people so can still produce more force
Age is associate with loss of muscle mass , what is this termed ?
Sarcopenia
Disease related muscle wasting is termed ?
Cachexia
