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Exercise Phys. Lecture 2

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winniesmith2's version from 2017-10-15 12:29

Section 1

Question Answer Column 3
Why does the cardiovascular system adapt to exercise?Acutely To increase oxygen delivery to working muscles by increasing blood flow to muscles and reducing delivery to low activity tissues
Why does the cardiovascular system adapt to exercise?: Chronically To deliver more oxygen to active muscle mass: More effective oxygen delivery during sub-maximal exercise and increased maximum oxygen consumption (VO2max)
What cardiovascular factors influence oxygen uptake and VO2max?• Cardiac structure and function • Blood (plasma) volume • Blood flow and distribution • Oxygen extraction (arterio-venous difference)
What is the Fick Equationused to work out VO2. = HR x SV x (a-v(with line over top)O2 difference. a-v¬ = arterio-mixed venous
Describe an Athletes Heart (McArdle)Larger left mass ventricle (g) than an untrained heart. Male hearts bigger than female. Largest hearts were male shot putters at 350g and College wrestlers at 330g (males). The largest female athletes heart was 210g for endurance runners.
LVMleft ventricular mass (g)
LVVleft ventricular volume (mL)
STSeptal thickness (mm)
(P)WT (posterior) wall thickness (mm)
Compare runners/swimmers hearts with wrestlers/shot putters wrestlers/shot have a bigger LV mass and a thicker LV wall but runners/swimmers have a larger LVV .
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Section 2

Question Answer
What is preload is the amount of blood in the ventricle before contraction (end diastolic volume). This determines cardiac muscle length before contraction. The most important determining factor for preload is venous return
What is afterloadis the pressure against which the ventricle must contract (vascular resistance, aortic mean pressure). The higher the afterload, the less blood will be ejected per heart beat.
What is the frank-starling mechanism is based on the length-tension relationship within the ventricle (the greater the stretch, the greater the contraction) • If ventricular end diastolic volume (preload) is increased, the ventricular fiber length is also increased, resulting in an increased ‘tension’ of the muscle
What is stroke volume determined by three factors: preload, afterload, and contractility.Cardiac output is therefore directly related to venous return and vascular resistance.
Describe Athlete's heart: mechanisms: cardiac enlargement (left ventricle)– Left ventricular mass > heavier in all athletes – Left ventricular volume > greater in endurance athletes • eccentric hypertrophy – Posterior wall thickness and septal thickness > larger in resistance athletes • concentric hypertrophy. Myocardial overload stimulates cellular protein synthesis and reduces protein catabolism.
Describe Athlete's heart: mechanisms: Endurance training • Pre-load = end-diastolic ventricular volume (determined primarily by venous return) • ↑ pre-load  ↑ stroke volume
what is stroke volume The amount of blood pumped by the left ventricle of the heart in one contraction.
Describe Athlete's heart: mechanisms: Resistance training • After-load = resistance to ventricular ejection (arterial pressure) • ↑ after-load  ↓ stroke volume
Describe endurance training adaptations on stroke volume • ↑ pre‐load (ventricular filling)  ↑ ventricular dimensions • ↑ diastolic filling time (due to bradycardia) • ↑ contractility • Maximal stroke volume ↑
Describe endurance training adaptations on heart rate• ↑ SV  ↓ HR to for the same cardiac output (sub‐ maximal exercise) • Note differences in slope and at absolute intensity (2.0 L∙min‐1) • Maximal heart rate unchanged
Describe endurance training adaptations on cardiac output . (Familiarise with graphs for each on lecture slides)Product of heart rate and stroke volume • Most significant adaptation  Vሶ O2max • Sub‐maximal exercise: Qሶ ↓, as increased O2 extraction to maintain Vሶ O2 (Due to better muscle oxidative capacity, higher (a‐vത)O2 difference)
Describe endurance training adaptations on oxygen extraction: (a-v¬)O2 difference • Training increases sub-maximal and maximal values in muscle • Improved cardiac output distribution to active muscles
(Training the heart through increases in blood volume?) Primary mechanism for blood volume increases: how – Increase in plasma proteins, mainly albumin (osmotic effect) – Increase in total body water via alterations in kidney function (reduced urine output and increased water retention)
Describe blood volume changes (w. schmidt found..)• Cross-sectional: higher blood volume in trained athletes • Haemoglobin concentration and the haematocrit remain more or less the same. However, ABSOLUTE plasma volume and red blood cell changes -> hypervolemia (so ratio stays the same but the amounts themselves increase) • Longitudinal: early changes = Plasma volume ↑ (10 days) then red blood cells ↑ (months)
Types of blood doping – Erythropoietin (EPO): induces production of red blood cells – Blood transfusions (own blood – autologous; another person’s blood: homologous)
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Section 3

Question Answer
Describe and compare acute blood redistribution in an athlete heavily exercising and at rest (according to research from Kenney/Wilmore/costill)During heavy exercise cardiac output increases (from around 5L/min at rest to 25 L/min). blood is directed away from the digestive system (percentage decrease from 20-25% to 3-5%) and the majority of blood flow goes to the muscle (increase from 15-20% to 70-85%). Muscle blood flow = 20L/min instead of 0.75L/min at rest. A higher percentage is also directed to the skin for heat loss (5-20% instead of 4-5% at rest).
How is acute blood flow regulated • Muscle metabolites and temperature • Pressure changes within the vessel • Dilator substances produced by the endothelium (such as nitric oxide (NO)) • Sympathetic activity -> reduced blood flow to low activity tissues (splanchnic, renal circulations)
What did armstrong and laughlin (1984) find in Rat blood flow redistribution following trainingIn trained rats, the muscle blood flow to Type 1 muscles (soleus and gastrocemius red) was higher, however for type 2 (gastrocnemius white) and hindlimb the amount of muscle blood flow was the same if not slightly less, showing that in trained athletes blood flow is redistributed more to the muscles in highest demand.
Describe capillarisation following training (kenney/wilmore/costill)well trained men have a higher capillary to fiber ratio at 1.5 (which increases slightly to 1.6 postexercise) compared to untrained men with a ratio of 1.1. Well trained men also have less muscle fibers per mm squared (suggesting they have stronger muscle fibers so require less). More capillaries allow blood flow to be redirected easier and have increased due to the need for more oxygen at these muscles. In well trained men the amount of muscle fibers decrease post training (440 to 414) but increase in untrained (557 to 576)
Aerobic training adaptations overview: increasing oxygen delivery to musclerevise poster
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