Adaptations to Strength Training Flashcards
What does mechanical overload in muscles cause?
Hypertrophy
Why would you need to overload?
To increase muscle mass - for aesthetic reasons or just to complete daily tasks (elderly).
What is muscle strength proportional to?
Cross sectional area.
How does power relate to CSA?
You can increase power output by increasing force.
You can increase force by increasing muscle CSA.
if you did a 12 week training programme what changes would occur?
Ability to lift weight - increase by 200%
Increase in isometric force by 11%
Increase in anatomical CSA by 4%
Why is greater increase in strength compared size.
1) Improve activation
- firing rate, motor unit activation
- coordination of syngerists
2) Change to muscle architecture
- pennation angle (angle of fibres)
3) Selective hypertrophy of type II fibre
What are the 2 basic requirements for muscle growth?
1) Increase rate of protein synthesis (decrease rate of degradation) or BOTH!
2) Provision of new nuclei.
Name the regulators of muscle growth.
Positive: IGF-1, Testosterone
Negative: Myostatin (GDF8)
How else can you increase muscle growth.
Increase intake of aa synthesis to increase protein synthesis to a point.
Explain how IGF-1 is a positive regulator of muscle growth.
Produced by the liver and other tissues locally.
Net release of IGF-1 from muscles after high intensity exercise.
INCREASES MUSCLE MASS.
(Direct infusion of IGF-1 intro muscle causes growth in mice…overexpression of IGF-1 in muscle - increase muscle mass).
Strength training and IGF-IEa gene transfer = enhanced adaptations.
IGF-1 also inhibits atrophy genes controled by the FOXO-P genes/TFs.
if no GH - pituitary removed - muscle still grows due to local IGF-1 production
Explain how testosterone is a positive regulator of muscle growth.
Steroid users have an increased fibre area.
Testosterone AND exercise = best”
TESTOSTERONE INDUCES MUSCLE GROWTH.
If trained leg peaks testosterone then train arms - no difference cf normal.
Inhibiting testosterone, inhibits growth.
If low testosterone : decrease growth
Normal : -
High: increase growth
(not linear).
Explain how Myostatin gene (GDF-8) is a negative regulator of muscle growth.
If you have a myostatin knock out mice - increase muscle growth.
Myostatin is secreted by muscle cells…myostatin dimers bind activin receptors…these phosphorylate and activate TF - Smad2/3 = growth inhibition.
Exercise causes decreased mysostatin
BUT lack of myostatin results in excessive muscle growth but impaired force generation.
Explain the provision of new nuclei.
A nuclei can look after up to ~2000micrometers squared myonuclear domain of cytoplasm.
There is a correlation between # of nuclei and muscle size.
Satellite cells - muscle stem cells (produce new nuclei and fibres).
Those who responded to training had increase satelitte cell #
