Exercise Physiology: Cardiovascular, Respiratory, and Adaptations

Resting HR change with training

Decreases due to increased parasympathetic (vagal) tone and increased stroke volume.

Submaximal HR change with training

Decreases at any given workload because the cardiovascular system is more efficient.

Maximal HR change with training

No significant change; max HR is age-predicted.

Resting stroke volume change

Increases due to larger LV size, increased blood volume, and stronger myocardium.

Submax stroke volume change

Increases due to improved venous return and contractility.

Maximal stroke volume change

Significantly increases; major factor in higher VO₂max.

Resting cardiac output change

Remains about the same; HR decreases but SV increases.

Submax cardiac output change

Slightly lower because of improved oxygen extraction.

Maximal cardiac output change

Increases greatly due to higher maximal stroke volume.

Resting systolic BP change

Decreases or stays the same due to improved vascular function.

Submax systolic BP change

Decreases because of lower total peripheral resistance.

Maximal systolic BP change

Increases to support higher cardiac output.

Resting diastolic BP change

Typically unchanged.

Submax diastolic BP change

Typically unchanged or slightly decreased.

Maximal diastolic BP change

Remains relatively stable.

Capillary density change with training

Increases, improving oxygen delivery, CO₂ removal, and a-vO₂ difference.

Why HR increases after 35 min (steady state)?

Cardiovascular drift: decreased plasma volume decreases stroke volume, so HR increases to maintain cardiac output.

Cranial nerve controlling resting HR

Vagus nerve (Cranial Nerve X).

Parasympathetic control of HR called

Vagal tone.

Hormones creating sympathetic response

Epinephrine and norepinephrine.

Arm vs leg exercise at same submax intensity

Arm exercise produces higher HR and BP due to less vasodilation and higher resistance; legs produce lower HR/BP due to more muscle and greater vasodilation.

Arm vs leg exercise at maximal intensity

Legs achieve higher VO₂max; arms produce higher HR/BP but lower VO₂max due to smaller muscle mass.

Blood redistribution at exercise

Muscle blood flow increases up to 80%, GI/kidney flow decreases, skin flow increases in heat, and veins constrict to increase venous return.

Why warm down after exercise?

Helps maintain muscle pump, prevent blood pooling, remove metabolic waste, and gradually return HR/BP to resting levels.

Muscle pump definition

Muscle contractions compress veins and use one-way valves to move blood toward the heart, increasing venous return and stroke volume.

Karvonen THR for HRmax 190

HRrest 68, 75%, 160 bpm.

Structure of myocardium

Short, branched fibers with intercalated discs; rich in mitochondria; desmosomes hold cells together and gap junctions allow electrical spread; LV has thickest wall.

Functional syncytium definition

Heart cells contract as one coordinated unit due to electrical coupling through gap junctions.

Frank-Starling Mechanism

Increased EDV stretches myocardium, increasing cross-bridge formation and contractile force, resulting in increased stroke volume.

Factors determining blood flow

ΔPressure / Resistance; resistance determined by vessel radius (most important), length, and viscosity.

Fick's equation for oxygen consumption

VO₂ = Q × a-vO₂ difference.

Fick's Law of Diffusion

Diffusion depends on surface area, membrane thickness, diffusion constant, and pressure gradient.

Bohr Effect

Increased temperature and acidity shift the O₂-Hb curve right, promoting oxygen unloading to muscles.

Central Command Theory

Brain initiates increased HR at exercise onset by withdrawing vagal tone; sympathetic activity then increases HR, SV, BP; blood is redistributed based on feedback from receptors.

Capacity of respiratory system

Respiratory system rarely limits performance in healthy individuals.

Surface area changes with training

Capillary density increases, improving gas exchange efficiency.

Stitch in the side

Possibly caused by diaphragm spasm, ischemia, ligament pull, or shallow breathing.

Dyspnea definition

Shortness of breath from inability to regulate CO₂ and H+; respiratory muscles fatigue.

Hypocapnia definition

Low CO₂ from hyperventilation causing dizziness and alkalosis.

a-vO₂ difference definition

Difference in O₂ content between arterial and venous blood; increases with exercise and training.

Lung volumes with training

Tidal volume increases with exercise; VC, RV, and TLC stay constant.

Vital capacity definition

Maximal air exhaled after maximal inhalation.

Minute ventilation definition

VE = tidal volume × breathing rate.

Maximal oxygen consumption components

Determined by cardiac output and a-vO₂ difference.

Atmospheric pressure at altitude

Barometric pressure decreases → PO₂ decreases → hypoxia.

Gas exchange in lungs

Occurs by diffusion following partial pressure gradients.

Hyperventilation effects

Decreases CO₂, reduces drive to breathe, can cause dizziness.

Breath holding physiology

CO₂ rises until a "breaking point" forces breathing.

Breathing pure oxygen

Increases O₂ content briefly but does not greatly improve performance.

Altitude adaptations

Increased ventilation, increased EPO, increased RBCs and hemoglobin.

Oxyhemoglobin curve—right shift

Caused by increased temperature, CO₂, and H+; improves oxygen unloading.

O₂ transport in blood

98% bound to hemoglobin, 2% dissolved in plasma.

CO₂ transport in blood

60-70% as bicarbonate, 20-33% bound to hemoglobin, 7-10% dissolved.

Estimating VO₂max

Based on HR response during submax tests like YMCA cycle, Rockport walk, and treadmill tests.