L11.1 Ageing

Question 1

What is sarcopenia and does cachexia contribute to it?

Answer 1

• Sarcopenia: age-associated loss of skeletal muscle mass & function
• Measured in patients who are bedridden or gait speed of <1m/s & appendicular lean/fat ratio <2 SD of norm
• Cachexia may be a component of sarcopenia but conditions are not the same

Question 2

3 criteria for sarcopenia?

Answer 2

1. ↓ muscle mass
2. ↓ muscle str
3. ↓ physical performance

• Sarcopenia identified by 1 + 2 or 3

Question 3

Causes of sarcopenia

Answer 3

1. Denervation
2. Hormones
3. Impaired Ca2+ release & reuptake
4. Inflammation
5. Fibrosis

Question 4

Effect of ageing on physical performance?

Answer 4

• Even if you maintain training at an elite level → ↓ performance with age
• ↑muscle fats & infiltration of connective tissues
• Fast muscles atrophy quicker than slow twitch

Question 5

Neuromuscular effects associated with sarcopenia?

Answer 5

• Ageing → selective denervation of type 2 MU → ↓Vol of muscularture & remodelled type 2 with type 1 MU
  
  • Fast fibres may be denervated and dies, or receive innervation from new axonal branches called SPROUTS → remodel fast fibres
• Significant interplay b/w neural & muscular feedback pathways
• May have demyelination of muscle fibres → affects neurotransmission
• Gradual changes in post & pre-synaptic components
  
  • Changes in motor end plates
  • Terminals are longer but lose side branches → ↑size of motor end plates

Question 6

Initial muscle wasting?

Answer 6

• Slowing of contraction first
• Impaired SR function → contributes to fall related injuries

Question 7

Summary of muscle wasting effects

Answer 7

1. Muscle fibres: ↓ size & #
2. Sat cells: ↓ Response & #
3. E-C coupling: ↓Ca2+ & coupling
4. Adipocyte infiltration: ↑ inter/intra muscular adipose tissues
5. Mitochondria: ↓ enz content & #
6. Myofilaments: ↓ function, force & elasticity
7. Fibre type transformation: Fast → Slow

Question 8

Hormonal levels with ageing?

Answer 8

• ↓anabolic hormones (GH, IGF-1, testosterone)
• ‘top up’ strategy is not successful (when not used in conjunct with weight lifting exercises)

Question 9

Interventions to attenuate sarcopenia

Answer 9

• Incorporation of str training → maintain both type 1 & 2 fibres
• Older muscles still have the adaptive capacity to challenge
• Take str/aerobic/flexibility/balance into design of exercise