Week 8: physiological basis of strength Flashcards
what is strength defined as the ability to generate?
Force
How is power defined as? Whats it’s equation?
the rate of work. Work is the product of force and distance.
Power = Work/Time
What are 3 main functions of the skeletal muscle
- Force generation for locomotion and breathing
- Force generation for postural support
- Heat production during periods of cold stress
What is an epimysium, Perimysium, and endomysium?
Epimysium - CT layer surrounding muscle
Perimysium - CT layer surrounding individual fascicle
Endomysium - CT layer surrounding each fibre in fascicle
What is a sarcolemma?
Membrane surrounding muscle cell
What does the myofibrils consist of?
Repeating sarcomeres which containts thick myosin and thin actin.
What is the sarcoplasmic reticulum and its function?
Network of membranous channels, parallel to fibres. It’s function is to release and store calcium.
What are T-tubulues and its function?
Another set of channels but at a perpendicular angle. It propagates action potentials
What is the main neurotransmitter responsible for communication?
Acetlycholine
What is one theory of how actin and myosin interact with each other.
Ca2+ binds to the troponin complex causing conformational change in the troponin complex hence tropomyosin, permitting formation of strong cross-bridges.
How much does the contraction cycle reduce length?
Around ~1%
What role does the ATP have during a contraction cycle in the muscle cell?
ATP is binded to the myosin head allowing the myosin head to release from actin
During Excitation-contraction coupling where does around 30% of the ATP get used?
~30% of Calcium is used to pump calcium to the sarcoplasmic reticulum
What may be problematic in the future regarding gene manipulation?
There may be such thing as gene doping, where athletes may get a certain advantage over others. Anti-doping agency needs to stay on top of controlling ones gene adaptations
What are some of the factors that the force generated by a muscle group dependent on?
- Type of contraction
- The arrangements of the muscle fibres
- Initial length of muscle fibres
- no. and type of motor units recruited
- nature of the neural stimulation
What is the difference between isometric, isotonic and isokinetic?
Isometric - NO change in joint angles
Isotonic - change in joint angles and movement
Isokinetic - constant speed over ROM
What are some muscle fibre arrangements?
fusiform, unipennate, bipennate and multipennate
What are some characteristic of the fusiform and pennate?
fusiforms run parallel to muscle’s long axis. Rapid shortening.
Pennate bundles of fibres are at angle of up to 30 degrees. Slow but greater force and power production due to greater cross-sectional are.
what is defined as a motor unit?
a motor neuron and all the fibres innervated by it.
Explain the nature of the stimulus for a muscle contraction
there are simple twitches that do not represent a muscle contraction rather the summation created a tetanus stimulus which contracts muscle
Are the highest movement velocities achieved by high or low forces?
low forces
Why does power output start to drop at higher velocities? (Explain mechanically speaking)
It is because actin and myosin may not completely attach to each other due to the high velocity.
Immediately following an eccentric phase, the concentric phase increases the power output compared to normal concentric activity.
What type of training exploits this?
Plyometric exercise.
What are some of the skeletal muscle receptors? What are it’s functions?
Chemoreceptors, Golgi tendon Organs, and muscle spindles.
Chemoreceptors - gives feedback to SV system and respiratory systems
GTO - feedback about how much tension is developed. Considered a safety device
muscle spindles - Gives sensory feedback about muscle length. Can cause rapid shortening.
