Week 4 - Muscle Ageing Flashcards
What are the impacts of muscle ageing
Strength is lost with age
Greater loss in lower body limbs
Muscle power in lower group
Muscle power declines with age.
Older adult has greater subcutaneous fat and intermuscular fat
What underlies the functional decline of muscle mass
(ON SHEET)
Average rate of muscle mass loss is approx 8% per decade, until 70 years old where it increases to 15% per decade.
Muscle biopsies can show muscle atrophy - fibres get smaller with age, especially type II. Losses in muscle strength are far greater than muscle loss
What underlies the functional decline of muscle quality
Aging increases fat accumulation in muscle - more fat, less muscle within the muscle, more fat in and between muscle
Losses in muscle mass don’t completely explain strength loss
What underlies the functional change in neuromuscular alterations
increased age = less motor units
What are the functional consequences of losing motor units
Results in muscle fibers becoming denervated
This causes muscle atrophy and potential fibre loss.
However there are adaptive processes that act to rescue force production loss from affected muscle fibers
How does denervation and collateral re-innervation alter muscle characteristics
(ON SHEET)
Increase co-expression of myosin isoforms
Decrease force output
Decrease velocity of contraction and thus power
Whats the effects of reinnervation of fibres
Increase size of motor units
reinnervation preserves some muscle mass
What are other changes that occur to excitation-coupling process
(ON SHEET)
Changes to excitation-contraction coupling leads to decreased Ca2+ release from sarcoplasmic reticulum
Whats the effect of changes in sarcoplasmic reticulum function
(ON SHEET)
Decreased Ca2+ uptake
Whats the effect of the slowing of the myosin molecule
decreased intrinsic speed of shortening
Whats the effect of reduced acto-myosin cross bridges
Decreased force output per muscle fibre
How is fatigue resistance impacted with old age
More type II fibres innervated by type I motor units so act more like Type I
What is a master athlete
Anyone aged 35 or over, competing in track and field, road running, cross country, or race walking
What are the muscle characteristics of master athletes
(ON SHEET)
Lifelong exercise does not minimise motor unit increase or inefficiency.
Fibre loss is inevitable with age but type I better preserved in these master endurance athletes
Same force as someone 30 years younger.
Muscle deterioration not removed but not as severe
