Lecture 29 Flashcards
What influences fiber recruitment in muscles?
Fiber recruitment depends on intensity and duration of training. (Hennemen’s size principle)
What is the problem with using electrical stimulation as the principle stimulation of muscles in the lab when studying them?
Electrical stimulation activates all fibers regardless of fiber type.
Nevertheless, adaptive changes during physical activity are similar to those during electrical stimulation.
What is the problem with the adaptations to physical activity?
Adaptations to physical activity are easily and rapidly reversible.
Increase in oxidative enzyme activities during endurance training may take months.
And losing the gains can occur within a few weeks after stopping training.
What do muscles adapt to? What are the limitations of this method?
Muscles will adapt optimally to exercise that moderately exceeds their capacity. This is limited by physiological and anatomical limitations.
What is General Adaptation Syndrome (GAS)?
General Adaptation Syndrome states that initially there is a challenge to the system which is followed by growth or improvement and then a plateau, This plateau can be followed by exhaustion which can have the opposite effect.
What other factors influence limitations to muscle changes?
Not everyone has the same adaptive potential with some people having genetic advantages over others. (eg. Fast twitch fibers in sprinters)
What are the differences between activating muscles using voluntary muscle contractions and electrical stimulation in the lab?
Voluntary muscle contractions:
Muscle tension can be varied over a wide range by varying the number of active motor units to produce smooth movements or contract them individually during a sustained contraction.
Electrical stimulation stimulates all the motor units synchronously with the same impulse pattern.
What are the advantages to electrical stimulation?
Standardised model -
adaptative responses occur in a reproducible well-defined way.
Elicits maximal adaptive potential of the muscle.
Adaptations occur in a shorter period of time.
Adaptations restricted to target muscle; therefore minimal systemic effects.
Does not induce muscle damage in rodents allowing for a clean investigative model.
What is progressive overload?
Progressive overload is gradually challenging muscles and the muscle adapts to this gradually increasing stimulus.
*This is used in resistance training to lift heavier weights and build muscle
What are some adaptations of skeletal muscles to endurance training?
Changes to central and peripheral circulation, increase in Cardiac Output, increase in muscle blood flow, improved muscle metabolism and respiratory capacity.
What is the response of muscles to endurance training?
Endurance training causes little or no change in fiber type proportions and little or no changes in fiber size.
Subtle changes are seen among fiber subtypes (2b ->2a)
Capillarisation
15% increase in number of capillaries after 8 weeks of training.
Greater exchange of gases and fuels between blood and working muscles.
Improvement in mitochondrial activity and a shift to fat dependence rather than carbohydrates.
How are muscle size and strength related?
Muscle size is generally correlated with strength. However, this is not always the case.
What does chronic weightlifting result in?
Chronic hypertrophy which results in increase in size of muscles at the fiber levels
What are first changes seen in strength training in response to exercise?
First changes seen with strength training are often due to changes in neural factors and then this plateaus and is followed by increases during times of advanced training.
What are some adaptations to resistance training?
All muscle fibers get bigger because they are recruited in a consecutive order to produce high levels of force.
In advanced lifters the CNS might adapt by allowing athletes to recruit some motor units not in consecutive order. Allowing production of greater power instantly.
