Week 8: physiological basis of strength

Question 1

what is strength defined as the ability to generate?

Answer 1

Force

Question 2

How is power defined as? Whats it’s equation?

Answer 2

the rate of work. Work is the product of force and distance.

Power = Work/Time

Question 3

What are 3 main functions of the skeletal muscle

Answer 3

1. Force generation for locomotion and breathing
2. Force generation for postural support
3. Heat production during periods of cold stress

Question 4

What is an epimysium, Perimysium, and endomysium?

Answer 4

Epimysium - CT layer surrounding muscle

Perimysium - CT layer surrounding individual fascicle

Endomysium - CT layer surrounding each fibre in fascicle

Question 5

What is a sarcolemma?

Answer 5

Membrane surrounding muscle cell

Question 6

What does the myofibrils consist of?

Answer 6

Repeating sarcomeres which containts thick myosin and thin actin.

Question 7

What is the sarcoplasmic reticulum and its function?

Answer 7

Network of membranous channels, parallel to fibres. It’s function is to release and store calcium.

Question 8

What are T-tubulues and its function?

Answer 8

Another set of channels but at a perpendicular angle. It propagates action potentials

Question 9

What is the main neurotransmitter responsible for communication?

Answer 9

Acetlycholine

Question 10

What is one theory of how actin and myosin interact with each other.

Answer 10

Ca2+ binds to the troponin complex causing conformational change in the troponin complex hence tropomyosin, permitting formation of strong cross-bridges.

Question 11

How much does the contraction cycle reduce length?

Answer 11

Around ~1%

Question 12

What role does the ATP have during a contraction cycle in the muscle cell?

Answer 12

ATP is binded to the myosin head allowing the myosin head to release from actin

Question 13

During Excitation-contraction coupling where does around 30% of the ATP get used?

Answer 13

~30% of Calcium is used to pump calcium to the sarcoplasmic reticulum

Question 14

What may be problematic in the future regarding gene manipulation?

Answer 14

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

Question 15

What are some of the factors that the force generated by a muscle group dependent on?

Answer 15

• 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

Question 16

What is the difference between isometric, isotonic and isokinetic?

Answer 16

Isometric - NO change in joint angles

Isotonic - change in joint angles and movement

Isokinetic - constant speed over ROM

Question 17

What are some muscle fibre arrangements?

Answer 17

fusiform, unipennate, bipennate and multipennate

Question 18

What are some characteristic of the fusiform and pennate?

Answer 18

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.

Question 19

what is defined as a motor unit?

Answer 19

a motor neuron and all the fibres innervated by it.

Question 20

Explain the nature of the stimulus for a muscle contraction

Answer 20

there are simple twitches that do not represent a muscle contraction rather the summation created a tetanus stimulus which contracts muscle

Question 21

Are the highest movement velocities achieved by high or low forces?

Answer 21

low forces

Question 22

Why does power output start to drop at higher velocities? (Explain mechanically speaking)

Answer 22

It is because actin and myosin may not completely attach to each other due to the high velocity.

Question 23

Immediately following an eccentric phase, the concentric phase increases the power output compared to normal concentric activity.
What type of training exploits this?

Answer 23

Plyometric exercise.

Question 24

What are some of the skeletal muscle receptors? What are it’s functions?

Answer 24

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.