Ch. 13 Flashcards
What is the principle of specificity?
Refers to the effect that exercise training is specific to the muscles involved in that activity, the fiber types recruited, the principal energy system involved, the velocity of contraction, and type of muscle contraction
What is maximal oxygen uptake?
Measure of the maximal capacity of the body to transport and use oxygen during dynamic exercise using large muscle groups
What are the three principles of training?
- Overload
- Specificity
- Reversibility
What is overload?
Principle that refers to the fact that an organ system or tissue must be exercised at a level beyond which it is accustomed in order to achieve a training adaptation
What is the principle of reversibility?
Refers to the fact that the fitness gains by exercising at an overload are quickly lost when training is stopped and overload is removed
What are typical variables that constitute the overload?
- intensity, duration, and frequency of exercise
If a muscle is engaged in endurance exercise training, what are the primary adaptations?
- increase in capillaries and mitochondria volume which increases the capacity of the muscle to produce energy aerobically
If muscle is engaged in heavy resistance training, what are the primary adaptations?
- increase in quantity of contractile proteins
Extremely high VO2 max values possessed by elite female and male endurance athletes are the genetic gift of what?
- large cardiovascular capacity
- high % of slow muscle fibers
About 50% of individuals VO2 max is determined by
- genetics along with environmental influences
Endurance training programs that increase VO2 Max commonly involve?
Also what % intensity is it at?
- continuous dynamic exercise using large muscle mass (running, cycling) for 20-60 mins per session
- 3 or more times per week @ intensity >50% VO2 max
It. Is estimated that the heritability of training gains in VO2 max is approximately what %?
47%
In addition to genetic factors, what other 2 factors of endurance training have an important impact on the magnitude in training induced changes in VO2 max
Intensity and duration
The large increase in VO2 max with the 10 week training program was due to what?
Higher intensity, frequency, and duration of training
Endurance training programs increase that VO2 max involve
- Large muscle mass in continuous activity for 20-60 mins per session
- 3 or more times a week
- intensity of 50-85% VO2 max
What 2 activities increase VO2
Endurance training programs and high intensity interval training
The largest training induced increases in VO2 max occur in those who are genetically gifted and referred to as what?
High responders
What is the calculation of oxygen consumption via fick’s equation?
- VO2 max = maximal cardiac output x (maximal aVO2 difference)
- product of systemic blood flow (cardiac output) and systemic oxygen extraction (arteriovenous oxygen difference)
What is A-VO2 difference?
A measure of how much oxygen is removed from arterial blood and used by tissues
Research reveals that in UNTRAINED subjects, relatively short duration of endurance training increases what?
- VO2 max and maximal cardiac output but does NOT increase aVO2 difference
Studies review that a longer duration of training (32 months or more) increases VO2 max by increasing?
- maximal cardiac output
- maximal a-VO2 difference
Following both short and long duration of endurance training, exercise induced increase in maximal cardiac output is ENTIRELY due to
- increases in stroke volume because maximal heart rate remains constant or slightly decreases
What is stroke volume?
- amount of blood ejected from the heart with each beat and is equal to the difference between EDV and ESV
Increase in resting stroke volume in endurance trained athletes is due to
Increased EDV at rest that results from increased stretch of myocardium because of the increased ventricular filling time associated with slower resting heart rate (bradycardia) that occurs following endurance training
What three factors can increase stroke volume?
- Increase in EDV (preload)
- Increased cardiac contractility
- Decrease in total peripheral resistance (after load)
3 factors that increases EDV
- Plasma volume increases
- Increase filling time and venous return
- Increase ventricular volume
Cardiac contractility refers to what?
- strength of cardiac muscle contraction when fiber length (EDV), afterload (peripheral resistance), and heart rate remain constant
Afterload refers to what?
Peripheral resistance against which the ventricle is contracting as it tries to push blood into the aorta
All training induced increases in maximal cardiac output must come from what?
Increases in stroke volume
How does endurance training increase cardiac pumping?
Increases left ventricular twist mechanism resulting in increased stroke volume
What does the increases in mitochondrial number following endurance training do?
Increases the muscle fibers ability to consume oxygen and also contribute to the expanded a-VO2 differences
What makes mitochondrial number not a key factor limiting VO2 max?
Capacity of the mitochondria to use O2 exceeds the capability of the heart to deliver O2
The increased capacity of the muscle to extract O2 following training is due to increase in
- Capillary density
2. Increase in mitochondrial volume
Endurance training induced increases in VO2 max following many months of training are due to an elevation in both:
- cardiac output and a-VO2 difference
- increase in a-VO2 difference is due to increased O2 extraction from the blood
What does the enlarged capillary density in trained muscle do?
Accommodates the increase in muscle blood flow during maximal exercise, decreasing the diffusion distance to the mitochondria, and slows the rate of blood flow to allow more time for O2 diffusion from the capillary to muscle fiber
What did Dr. Holloway and Dr. Saltin do?
Holloway: contributes to our understanding of the effects of endurance training on muscle and metabolism and how they affect endurance performance, heart disease, diabetes
Saltin: improved understanding of training induced changes in VO2 max and the regulation of fuel utilization in skeletal muscle during exercise
Common endurance training induced changes include:
- Increases in the percentage of slow muscle fibers
- increased mitochondrial volume in fibers
- added ability for muscle to metabolize fat, improved muscle antioxidant capacity
- increased capillary density
Why is afterload important?
It is important because when the heart contracts against a high peripheral resistance, stroke volume will be reduced
What are some endurance training induced adaptations:
- More rapid transition from rest to steady state exercise
- Reduced reliance on the limited liver and muscle glycogen stores
- Numerous cardiovascular and thermoregulatory adaptations that assist in maintaining homeostasis
Endurance training induced changes in fiber type how?
- endurance training results in a shift in fast to slow muscle fiber type
- slow myosin isoforms have lower myosin ATPase activity but are able to perform more work with less ATP utilization
- this fast to slow shift in myosin isoform is important because it increases mechanical efficiency and can potential improve endurance
The magnitude of exercise induced fiber type shift in endurance training is dependent upon
Intensity and duration of training sessions along with total years of endurance training
Endurance training induced changes in capillarity how?
- endurance training increases the capillary supply to skeletal muscle fibers of trained individuals
- exercise induced capillarization in the skeletal muscle is advantageous because diffusion distances for oxygen and substrate delivery to muscle fibers is reduced
Two sub populations of mitochondria exist in skeletal muscle:
- one population results immediately beneath the sarcolemma (sub sarcolemma mitochondria)
- second and larger group of mitochondria (80%) is dispersed around the contractile proteins (intermyofibrillar mitochondria)
How does endurance training impact mitochondrial content in skeletal muscle fibers?
- rapidly increase volume of both mitochondrial sub populations in active skeletal muscle fibers
- mitochondrial volume can increase in muscle fibers within first 5 days of training
Prolonged endurance training can increase muscle mitochondrial volume by? During which weeks?
- increase muscle mitochondrial volume by 50-100% within the first 6 weeks of training
What is the process in which the primary source of ATP during steady state phase of exercise is formed?
- At onset of exercise ATP is converted to ADP and P in muscle fibers to develop tension
- Increase in ADP [] in cytoplasm is immediate stimulus for ATP producing system to meet the ATP demands of cross bridges
- Phosphocreatine responds immediately to this ATP need, followed by glycolysis, and finally mitochondrial oxidative phosphorylation
Why is the steady state VO2 measured during a submaximal work test not affected by endurance training?
Mitochondria in working muscles are consuming the same numbers of O2 molecules per minute
Since training results in an increase in size of mitochondria in muscle, the ATP producing chore handled by mitochondria differs between untrained nad trained skeletal muscles how?
- supp
Suppose an untrained muscle cell has only one small mitochondrion and a breakdown of 100 units of ATP per minute is needed for the muscle to consume 2.0 liters of O2 per minute to sustain a constant level of exercise
- The breakdown of 100 units of ATP/ minute results in the formation of 100 units of ADP/minute in the cytosol of the fiber
- after training, when the size of the mitochondria in the cell has doubled, the rate of ADP transportation into the mitochondria has also doubled
- therefore, the ADP concentration in the cytosol increases only half as much because of the additional mitochondria present to take up ADP
ADP [] in the cytosol increases only 1/2 as much because of the additional mitochondria present to take up ADP is important for 2 reasons:
- The lower ADP [] results in less phosphocreatine depletion because the reaction for this is:
[ADP] + {PC] ——-> [ATP] + {C] - The lower ADP [] in cell also results in less stimulation of glycolysis and therefore a reduced production of lactate and H+
Collectively the reduced stimulation of glycolysis is due to lower ADP and higher PC [] following endurance training results in
- Less reliance on anaerobic glycolysis to provide ATP at the onset of exercise
- the net result is a lower oxygen deficit, less depetion of phosphocreatine, and reduction in lactate and H formation
What is the primary fuel for the nervous system
Plasma glucose
What are some training induced changes in muscle fuel utilization
- endurance training results in decrease use of glucose as fuel and an increase in fat metabolism during prolonged submaximal exercise
- these changes spare plasma glucose and increase the reliance on fat as a fuel source in skeletal muscle during exercise
Dax
Resistance training increaes muscular strength by changes in both
Nervous system and increase in muscle mass
In training studies of short duration, what factors play a major role in n the gain in strength?
How about long duration?
- neural adaptations related to learning, coordination, and ability to recruit primary muscles
- an increase in muscle size plays major role ins strength development
A significant portion of strength gains that occur with resistance training, is due to
Neural adaptation and NOT enlargement of muscles
The neural adaptations that occur in response to resistance training result in an improved ability to
Recruit motor units, alter motor neuron firing rates, enhance motor unit synchronization, and result in removal of neural inhibition
How does resistance training increase skeletal muscle size
By increasing their size of existing fibers (hypertrophy) or increasing their number of total fibers (hyperplasia) in muscle
Hyperplasia
- increasing the total number of muscle fibers within a specific muscle
- most 90 to 95% of increase in muscle size following resistance training occurs due to an increase in muscle fiber size (hypertrophy) and NOT hyperplasia
What is considered the primary means to increase muscle size during long term strength training?
Fiber hypertrophy
There is evidence that with high intensity training, changes in muscle size can be detected within how many weeks?
3 weeks
Weight training elicits a greater degree of hypertrophy in which type of fibers?
Type II fibers
The resistance training induced increase in fiber cross sectional area results from an increase in
Myofibbrillar proteins (actin and myosin) - increase in actin/myosin filaments in fiber occur due to addition of sarcomeres in parallel to existing sarcomere
Strength training induced shifts in muscle fiber types appear to be less prominent than endurance training transformations because
- all of the change in fiber type is a movement from type IIx to type IIa with no increase in type I fibers
Whether resistance training improves muscle oxidative properties is dependent uptown
Duration of training period and volume of exercise performed
Can resistance training improve muscle antioxidant enzyme activity?
Resistance training increased the activities of 2 important muscle antioxidant enzymes by almost 100%
- provides cellular protection against oxidative damage associated with free radicals
Single bout of resistance exercise increases muscle protein synthesis by
50-150% within 1-4 hours following exercise in both trained and untarined individuals
Why does exercise induced muscle hypertrophy typically occur more rapidly in untrained subjects?
Post exercise protein synthesis remains elevated for longer period time in untrained individual
Exercise induced increase in muscle protein synthesis is largely due to
Increase in the amount of protein synthesized per molecule of mRNA rather than an increase in total mRNA
- increases efficiency of translation
What is a major regulator of protein synthesis and muscle size?
MTOR
2 signaling molecules that directly activate mTOR include
Phosphatic acid and Rheb (short for Rays homolog)
What is tuberous sclerosis complex? (TSC2)
Molecule that inhibits activation of mTOR
