Muscle damage Flashcards
What type of exercise is muscle damage associated with?
Eccentric exercise - due to increase in CK
What is muscle damage diagnosed and characterised by?
Diagnosed by: increases in myoglobin and CK (creatine kinase) levels.
Characterised by: structural + functional changes
1) Sarcomeric disruption, Z-disc streaming
2) TT disruption leading to leaky ion channels
3) Calpain activation ((calcium-activated protease)) increasing membrane permeability (Evans blue dye)
4) Increased inflammation
5) Increased activation of satellite cells
What is an indicator of muscle damage?
Creatine kinase
What occurs during an eccentric contraction? (Sarcomeric disruption, Z-disc streaming)
- Muscles lengthen
- Contracts at the same time
= MD
Titin important in maintaining structure of sarcomere: disruption causes inability to hold sarcomere anymore
What is the effect of eccentric exercise on TT structure?
Takekura et al.: Looked at rat ST and FT fibres
- Quantified by looking at no. of horizontal TT (the orientation)
- No. of TT that were disrupted with muscle damage increased for both ST and FT fibres
(Freq. of occurrence of longitudinally oriented TT segments was more striking 2-3 days after exercise and seemed to be related to Z line loss)
- Disrupt structure of TT = disrupt channel for calcium
- Lots of unwanted calcium enters cells
- RESPONSE: system thinks this is a problem and induces/activates pathway for degradation and proteolysis = why we have calpain activation
What is calpain activation (calcium-activated protease)?
- Protein involved in degradation of muscle
- Only active bc of calcium, so degradation occurs in SMF bc of leaky calcium channels = affects protein inside muscle e.g. muscle membrane = fragile
How is inflammation associated with muscle fatigue? (LINK ISHD)
Light mic after eccentric exercise:
+7 days: aggregates of mononucleated cells
+12 days: aggregates increase = indicator of inflammation (delayed response to disruption)
+20 days: disappears and back to normal = transient
How is increased activation of satellite cells associated with muscle fatigue?
More satellite cells = hypertrophy afterwards
“No pain, no gain” = positive effect
What is the involvement of macrophages and T cell infiltration with satellite cells?
- Constant damages try to activate satellite cells
- At a certain point the system gets exhausted and can’t activate sat. cells anymore
= the point where the disease gets more severe - Can’t activate sat. cells anymore = can’t make muscle anymore
Is resistance to muscle fatigue related to polymorphism (SNP)?
- Variations in genes > affects actual protein > variations in proteins
- Some people have, some people don’t
What is the role of ACTN3?
- Causes variation between individuals
- Related to alpha actinin in the muscle sarcomere, Z-disc (thick + thin, at each end have a dark band = Z-disc; hundreds of proteins, imp. for structure, main one = alpha actinin - encoded by ACTN3)
- Variation may have a small protective effect on the sarcomeres
- Under debate - as done on a small pop
