12. ageing and muscle Flashcards
define sarcopenia
the age related loss of muscle mass and function
as appendicular skeletal muscle mass being <2 standard deviations below the mean of a young reference group
ageing demographics
By 2020, 20% of the UK population will be over 65 years of age, mainly due to increasing longevity, particularly in the 80 years and over age group. One in three born today are predicted to live to >100 years of age.
ageing and muscle
loss of quanitity, strength and quality
Muscle Functional Changes - quality
No change in slow-twitch muscle fibre area with ageing, but a 35% loss of fast-twitch muscle fibre area
high proportion of fast twitch relates to high muscle power output
mechanisms of sarcopenia
insufficient protein intake
anabolic blunting: decline in myofibrillar and sacroplasmic protein, decreased sensitivity- anabolic resistance- can increase protein intake for acute effect
mechanisms of sarcopenia
loss of motor function
loss of spinal motor neurons and motor units
Glucose tolerance and ageing
- Glucose tolerance is determined by the balance of insulin secretion and insulin action and deteriorates with age.
- Insulin secretion does not appear to be reduced with increasing age, but this is not a unanimous opinion as beta cell function has been proposed to decline with ageing.
- insulin resistance (impaired insulin action) in healthy elderly subjects.
However, few studies have taken into confounding variables such as general health, muscle mass, decline in habitual physical activity, changes of liver size and delays in carbohydrate absorption that accompany age.
•Maintaining physical fitness throughout middle and older age and so reducing hyperinsulinaemia will therefore have clear health benefits.
Ageing and muscle health: impact of inactivity
physiological ageing major feature of inactivity (even in young adults)
Positive effects of resistance exercise in treating sarcopenia
- Sarcopenia is partly reversible using resistance exercise training interventions (even in 90 year old care-home residents). Note increasing dietary protein intake per se will not reverse sarcopenia.
- Training has positive effects on both muscle mass and muscle quality.
- Question: How much of anabolic resistance and insulin resistance are therefore explained by inactivity?
Exercise -
molecular mechanisms
which hormones are decreased with ageing?
how can exercise help with this?
- The molecular mechanisms by which resistance exercise positively impacts upon muscle mass and function are likely to be linked to increases in muscle protein synthesis (Akt/mTOR signalling axis) and satellite cell activation.
- Little is known about the effects of resistance training on the loss of spinal motor neurons, motor units, and muscle fibre number.
- Aging is associated with a decrease in the concentrations of growth hormone (GH), testosterone (T), and insulin-like growth factor (IGF-1). Resistance exercise training may positively influence this.
- Exercise restores muscle insulin sensitivity and increases muscle capillarisation and mitochondrial mass, whilst reducing muscle fat mass.
confounding variables
- Sense of taste and smell diminish with age. This may lead to a lack of interest in food.
- Chewing problems. A large percentage of elderly people do not have all their own teeth. foods which are firmer and contain a lot of food fibre, such as fruit and vegetables are avoided.
- salivary glands shrink and less saliva is secreted. saliva plays a part in the digestion of starchy foods, dry food is avoided
•The digestive tract degenerates. Less gastric acid andenzymes needed for digestion are secreted; intestinal motility decreases and constipation increases. Although most of the nutrients are still well absorbed, calcium and iron absorption may decrease.
•Muscle co-ordination decreases making daily activities like cooking difficult
