Week 9: Neuromuscular Adaptations to Exercise and Training Flashcards
What are some of the physiological adaptations to resistance training?
Muscle fibres: Increase in number, size, and strength and become more specific
Capillary density: Doesn’t change in both bodybuilders or powerlifters.
Mitochondria volume and density both decrease
Twitch contraction time: decreases
Enzymes: creatine phosphokinase increase
Glycolytic enzymes: PFK increases and LDH is unchanged
Aerobic metabolism enzymes: increases in CHO and unknown for triglyceride
Basal metabolism increases
Intramuscular fuel store: increases in ATP, PCr, Glycogen, and unknown for triglyceride
VO2 max decreases with circuits and heavy resistance.
Connective tissue ligament and tendon strength increases and no change in collagen content observed.
Body composition: Decrease
%fat and increase in free fat mass
Bone: Increase in mineral content and density but no change in CSA
How does age affect muscle hypertrophy response?
There are less muscle hypertrophy response seen in elders and children. They rely more on the neural and other adaptations.
How does age affect muscle hypertrophy response?
There are less muscle hypertrophy response seen in elders and children. They rely more on the neural and other adaptations.
What is the relationship of hypertrophy in time? What would be observed in the first few training session regarding neural and muscular factors?
Hypertrophy benefits aren’t apparent for the first few training sessions but the adaptations are already seeing progress.
What is said according to the size principle of MU recruitment?
MU’s recruited according to their threshold of activation.
Possible that some high threshold MU’s cant be recruited in an unfamiliar task but training may result in increased activation hence increased MU recruitment and force
What is said according to the size principle of MU recruitment?
MU’s recruited according to their threshold of activation.
Possible that some high threshold MU’s cant be recruited in an unfamiliar task but training may result in increased activation hence increased MU recruitment and force
What may be beneficial about increased neural firing frequency for the muscle?
Higher threshold MU’s could be recruited more generating greater force
What are other neural factors that can contribute to muscle strength?
- Increased efficiency of MU recruitment - preferential recruitment of larger fast-twitch fibres.
- Increased efficiency of agonist activation - preferential recruitment of some muscles within a muscle group over others
- decreased co-activation of antagonists (Need more research over this) - Strength athletes generally show decreased agonist-antagonist co-activation.
- Decreased neural inhibition - Possible strength training may increase the ability to oppose autogenic inhibition (eg. GTO)
- Changes in NMJ activity - increase SA at synapse or increase dispersion of synapses leading to enhanced E-C coupling.
What is the definition of hypertrophy?
Increase in cell size. Not the muscle fibres that increases but the myofibril size and quantity increase
What are the possible mechanisms for hypertrophy?
Increased myofibrils, increased actin and myosin filaments, Increased Sarcoplasm, Increased connective tissue.
What may be the mechanism behind increases of myofibril numbers?
Thought to undergo longitudinal splitting into 2 or more daughter myofibrils. Increased sarcomere number in series. But length ususally changes during sport.
What is the difference of paracrine and endocrine signaling and how does exercise stimulate muscle growth in response to both endocrine or paracrine.
Endocrine: hormones traveling through the blood stream
Paracrine: Hormones traveling locally
When someone injures one leg and is immobilise but is able to train with the other leg, the trained leg would most likely experience muscle hypertrophy. If the endocrine hormones are the only ones working this wouldnt make sense as the untrained legs would also retrieve benefits. Therefore its explained that it must be both endocrine and paracrine signaling that elads to this result
What are the mechanisms of cell remodeling? Is it possible to convert fiber-types to another?
Mechanical stress may stimulate various extracellular signaling molecules, which may then stimulate previously dormant satellite cells to proliferate and differentiate.
Fusion of the new nuclei and incorporation into existing fibres probably enables formation of additional myofibrils.
Depending on training, type 2a muscle cells could develop anaerobic properties and vice versa
What is hyperplasia? What are the current evidence behind it?
Hyperplasia is when there is an increas in the number of muscle cell/fibres.
When hyperplasia is observed in animals, ther seems to be no hypertrophy response.
There is evidence in animals however, there is not much evidence in humans.
What are the causes to an improved power output following highly specific training?
Neural adaptations: Generally thought to be due to rapid recruitment of MU’s and increased firing frequency (net result = increased RFD: Rate of force development)
Improved intramuscular coordination: relationship between excitatory and inhibitory mechanism for one muscle for a specific movement.
Improved intermuscular coordintation: ability of all muscles involved in a movement (agonist, synergists and antagonists) to cooperate wholly with respect of an aim of movement
