Adaptations to Aerobic Training Flashcards
What happens to blood flow distribution during exercise?
- increased Q (cardiac output) aka blood pumped per min through heart
- BF is redistributed to accommodate active skeletal muscle
What is the intrinsic pacemaker of the heart?
SA (Sinoatrial Node)
What is the inherent rhythm of the SA Node?
100 bpm
Describe Parasympathetic tone
Vagus nerve is stimulated, reaches SA/AV node, releases ACH which decreases activity & HR
Describe Sympathetic tone
Cardiac Accelerator nerves innervate SA node/ventricles which signals the release of Catecholamines (epi/norepi), which increases SA node depolarization/HR
What is responsible for the initial increase in HR during a bout of exercise
Vagal Withdrawal (aka a decrease in parasympathetic tone)
What is the Frank-Starling Mechanism
an increase in diastolic volume stretches the cardiac muscle fibers and therefore increases the force of contraction
How does the body auto-regulate during exercise?
decrease in O2 in tissues stimulates vasodilation in working muscles, (+) in core temp, increase in CO2/acidity, Adenosine, MG, K+, Nitric Oxide in blood vessels, Sympathetic response shifts blood flow to exercising muscle and away from the Viscera
What happens to Systolic blood pressure during exercise? And Why?
It rises due to:
- increased HR/SV
- Muscle action/greater force required
- Vasodilation of exercising muscles allows more BF to drain from arteries
What happens to Diastolic blood pressure during exercise?
Should not change or decrease slightly
How does blood flow distribution during exercise change in the muscle?
15-20% at rest, 84% at max
How does blood flow distribution during exercise change in the liver?
27% at rest, 2% at max
How does blood flow distribution during exercise change in the Heart?
4% at rest and max
How does blood flow distribution during exercise change in the Skin?
6% at rest, 2% max
How does blood flow distribution during exercise change in the brain?
14% at rest, 4% max (absolute BV slightly higher due to Q)
How does blood flow distribution during exercise change in the kidneys?
22% at rest, 1% at max
What happens to blood volume at the onset of exercise? and Why?
BV decreases 10-20% because:
- hydrostatic pressure from muscular contraction squeezes fluid from bloodstream
- increase in osmotic pressure in intersititial fluid space around muscle cells due to accumulation of metabolites
- fluid lost to sweat
How does the body preserve blood volume during exercise?
- increase HR to maintain Q and offset small initial loss in SV
- Vasoconstriction of non-exercising muscle to maintain peripheral resistance
- release of hormones: Vasopressin/Adosterone to decrease water/NA+ loss from body
Define transient hypertrophy
the “pump” which results from fluid build-up (aka Edema) in interstitial and intracellular spaces of muscle from blood plasma
What is the limiting factor of Cardiac output during exercise
Venous Return (the rate of blood flow back to the heart)
What happens to Venous Return during isometric exercises?
VR decreases as the pump that sends back to the heart via contractions/one way valves is inhibited (this happens during weight lifting)
What is ventilation, and why does it increase right before exercise even begins?
Ventilation= volume of air breathed per minute
Catecholamines are responsible for increase in breathing rate
What is the humeral effect of ventilation?
receptors in the brain, carotid and aortic arteries sense chemical changes in blood (CO2, H+, K+) and responds by increasing ventilation
What is the neural effect of ventilation?
receptors in Medulla sense working muscle (or decrease in O2) via muscle spindles, GTOs, joint pressure receptors, and POSSIBLY mechanoreceptors in R ventricle
How does chronic aerobic exercise affect blood volume?
Increases (mainly plasma) up 12-20%
How does exercise affect the side of the heart?
L ventricle gets a little thicker (especially with resistance training)/bigger/more efficient (Frank-Starling Mechanism)
How does exercise affect the size of the heart?
10 bpm slower at rest, 20 bpm slower at sub-max, same at max
Chronic Adaptations of SV
increase at rest, sub-max, and max
Chronic Adaptations of Q
same or slightly decrease at rest/sub-max, increase at max w/ aerobic training (due to increase in SV)
Chronic Adaptations of AVO2 diff/explain
LOWER mixed venous O2 content because of
- greater O2 extraction at tissue level
- more efficient BF distribution to active tissue
Chronic Adaptations of BF
more BF to active tissue due to increased capillarization of trained muscle- new ones, existing ones get bigger, increased BV
Chronic Adaptions of BP
wont change much for normal, but can slightly decrease for pre/hypertensive
Chronic Adaptations to Neurons (3)
- motor unit recruitment- increased ability to contract simultaneously (usually recruits type 1 then type 2) and
- rate coding- faster time to peak force production of the MU
- Decreased co-activation of antagonist muscle
