Flashcards in Lecture 30 Deck (31)
What causes an adaptation?
The net effect of many different pathways in response to an activity
What is the difference between muscle activation in resistance/endurance exercise and electrical stimulation?
Endurance/Resistance exercise may not stimulate all muscle fibre types (ie. hennemenns size principle) if the intensity is low enough.
Electrical stimulation activates all muscle fibres.
What is a problem with adaptation to physical activity?
Its hard to obtain, and easy to lose.
Increasing enzyme activity/concentration is very slow to increase (months) and drop very rapidly when training is stopped.
Is it possible to transform muscle fibres from one type to another with electrical stimulation?
Is it possible to transform muscle fibres from one type to another with exercise?
Theoretically, it is possible if it is at a high enough intensity and occurring 24/7 for months.
Not very likely to happen
Name the transitions that occur in muscle fibres in response to exercise
Mucles may not transform fibre types, but will have transitions, ie. in between type 2B and type 1.
Subtle changes can be found in the myosin head heavy chain isoforms suited toward the appropriate fibre type
What is muscle plasticity?
Muscle isn't a static tissue, and can change in response to stimuli (exercise etc)
What can be said about muscle adaptation to physical exercise between individuals?
Not everyone has the same magnitude of response to physical activity, some more than others.
To what physical activity parameters do muscles maximally adapt to?
An exercise that moderately exceeds its capacity, meaning a gradual buildup is needed for maximal response.
Describe the general adaptation syndrome (GAS)
Alarm phase: a decrease in performance in response to the onset of exercise, responds with the resistance phase
Resistance phase: Performance rises as it responds to the exercise, such as protein synthesis, mitochondria production, capillaries etc.
Performance plateaus with the resistance phase.
Overtraining causes an exhaustion phase, gradual decrease in performance.
Name the limitations to physical adaptation
genetics - everyone responds differently
Not everyone has the same potential to adapt to physical exericse
Is why athletes with the same training have different responses
Name some differences between electrical stimulation of a muscle versus voluntary contraction
muscle tension can be varied across the active motor units - produces fine or smooth movements
muscles are recruited according to size and are activated asynchronously
Activation patterns ceased, all muscles contract at the same time
What are the advantages of electrical stimulation?
-standardised - adaptive response occurs in a reproducible manner
-maximum potential of the muscle is induced (all fibres recruited at once)
-can target a single muscle to minimise systemic effects
-muscle damage is not induced (rat models only)
Allows a clean way of investigating muscle adaptation
When a system or tissue is challenged with a stimuli to which it is unaccustomed
Over time, it will adapt to this stimuli, however, only muscles involved will adapt.
Describe some effects of low intensity but long duration exercise on a muscle (endurance)
increased capillary density and more mitochondria production and capacity, as well as central and peripheral circulation adaptation and increased CO
What is the effect of endurance exercise on fibre composition
little to no change in fibre size
fibres will not switch types
subtle changes among fast fibre subtypes (2B -> 2A)
chronic training can recruit 2B much faster
What is the effect of endurance exercise on mitochondria?
increased mitochondria capacity to produce ATP
increased number, size and efficiency
increased oxidative enzyme activity
release of FFA, shift to reliance on fat for ATP
What is the relationship between mitochondrial enzyme activity and maximal oxygen uptake?
(anaerobic enzyme activity decreases however)
Describe the adaptations of resistance exercise
What can be said about fibre numbers in muscle?
They are fixed from birth
What occurs during chronic hypertrophy?
increase in the size of individual fibres if gradual progression is used
What is hyperplasia?
An increase in fibre number
Why does muscle power lag behind muscle size?
In early training, most of the improvements to strength/power is due to neural drive, recruiting muscle fibres optimally.
Over time, once the adaptation sets in, the power improvement decreases, but hypertrophy occurs.
What is the effect of steroids on hypertrophy, neural drive and power?
An increase in both strength and hypertophy is seen, but neural drive is unaffected.
What is needed to elicit an increase in strength?
The muscle must be challenged above its maximal capacity to elicit adaptation to that exercise.
Describe two possibilities for hypoplasia
A heavily hypotrophied fibre splits into two or more daughter cells as its too big
Satellite cell proliferation after muscle damage
Japanese quail were found to have increased fibres post resistance exercise on their wings, suggesting hyperplasia is possible
Describe the experiment that suggests muscle fibres split in hyperplasia
A muscle fibre cross section is followed down gradually until it is seen to split into two.
On a different note, getting a cross section of a muscle, before and post exercise and counting fibre numbers isnt sufficient as only a small cross section of a much larger muscle can be obtained
Why are individualised training programs important?
Everyone responds a little differently to exercise
What are the 5 variables of resistance exercise training protocol?
Choice of exercise
Order of exercise
Number of sets
Length of rest period between sets