Week 4 Flashcards
what characteristics do the endurance phenotype have?
- Increased mitochondrial mass
- Increased oxidative enzymes
- Decreased glycolytic enzymes
- Increased slow contractile and regulatory proteins
- Decrease in fast-fibre area
What does high resistance training lead to?
- Increases in net mass
- Increase in Fibre cross-sectional area
- Increase in Protein content
- Increase in RNA content
what is tension
the force that a muscle exerts on the joint when its contracting
what is the load?
the force that the object exerts on the muscle
What are the types of muscle contractions
what is a muscle twitch
the mechanical response of a muscle fibre to a single action potential
what is the latent period?
this is a waiting time between action potential & tension in muscle increasing
what is the contraction time?
there is time between the start of the tension & peak tension
How does the load increasing affect muscle contractions?
- the latent period increases
- the velocity of shortening decreases
- the duration of the twitch shortens
- the distance of muscle shortening in the contraction decreases
how does load affect velocity
• a decrease in load means the muscle fibre can reach its maximum shortening velocity
• An increase in load can cause the concentric muscle contraction to become isometric
• an increase in load greater than peak tension causes the concentric muscle contraction to become eccentric
what is summation?
the increase of muscle tension of an action potential (increased frequency)
what is tetanus?
a state of sustained maximal contraction
what does muscle contraction speed depend on?
rate of cross bridge cycling
myosin heavy chain isoform
What are the mechanisms involved in muscle fatigue?
1- conduction failure: potassium accumulation in t tubules
2- lactic acid build up: affects proteins and calcium release
3- inhibition of cross bridges: so ADP and Pi build up
4- fuel substrates: blood glucose increased and dehydration
5- central command failure- failure of signals between brain and motor neurons
Techniques to determine fibre type
• Colour of fibre (~1900)
• EMG identification of motor units (~1950)
• Fibre speed and oxidative capacity (~1970)
• Myosin heavy chain isoform (~1990)
• Genomic nomenclature (~2000)
what does increasing strength lead to?
- increasing motor unit recruitment
- increased firing frequency
- increased muscle mass
What is muscle hyper trophy?
- increase in muscle fibre size
- addition of contractile proteins in muscle cell
- protein synthesis exceeds protein breakdown
What is hyperplasia?
- increase in number of muscle fibres
- more evidence to support hyperplasia in animals
what is the correlation between CSA and strength?
strong correlation between CSA and strength but no correlation between number of fibers and strength
what are the causes of muscle hyper trophy?
- Increase in protein synthesis, mTOR, ribosomal biogenesis
- Resistance training
- Increase in ACSA= area perpendicular to a muscle longitudal axis
- Increase in PCSA= (muscle mass x cosine of pennation angle) / (fibre length x muscle density)
how does the muscle chain in response to strength training?
- Occur in the muscle fibres
- Changes to the pennation angle and fascicle length
what influences the rate of hyper trophy
- Upper body has increased hypertrophy cuz lower body has pre habitual loading and a different fibre-type composition
- Women have 60-80% strength and CSA of muscles of men
- Absolute strength changes are greater in men
what is loss and gain of muscle?
loss = catabolism
gain = anabolism
what does a pennation angle muscle fibre cause?
- More sarcomere in parallel (increases force)
- More cross bridges
- More muscle fibers
