CV responses to exercise

Why does the CV system acutely adapt to exercise?

• To increase oxygen delivery to working muscles by increasing blood flow to muscles

• Reduce blood flow to low activity tissues

Why does the CV system chronically adapt to exercise?

• To deliver more oxygen to active muscle

• More effective oxygen delivery during sub-maximal exercise

• Increased VO2 Max

What is VO2 Max?

Maximum rate at which the body can use oxygen during intense exercise

What is Haematocrit and the equation for it?

• A measure of the proportion of red blood cells in the blood

What is Fick’s Equation?

VO2 = Heart rate x Stroke volume x AVO2 difference

What is preload?

The amount of blood in the ventricles before contraction (aka End diastolic volume)

• This determines the cardiac muscle length

• This is determined by venous return

What is Afterload?

The pressure against which the ventricles must contract

What occurs if afterload is too high?

Less blood will be ejected per heartbeat

What is starlings law?

An increase in preload (venous return) will cause an increased end diastolic volume

What characteristics of the heart do all athletes have?

• Heavier left ventricle mass

• Thicker left ventricle wall

• Thicker heart septum

What characteristics of the heart do endurance athletes have?

• Greater left ventricular volume due to an increased preload phase

• This causes eccentric hypertrophy

What characteristics of the heart do resistance athletes have?

• Large posterior wall thickness and septal fitness due to an increase in afterload and ventricular ejection

• This causes concentric hypertrophy

What adaptations to stroke volume occurs through endurance training?

• Increased preload phase

• Increased diastolic filling time due to bradycardia

• Increased contractility

• Increased maximal stroke volume

What adaptations to heart rate occurs through endurance training?

• Decreased HR due to an increased stroke volume

• Maximum HR remains unchanged

What adaptations to cardiac volume occurs through endurance training?

• Cardiac Output increases

• Increased AV02 difference, meaning greater oxygen usage by tissues

How is acute blood flow regulated?

• Muscle metabolites and temperature (e.g. CO2, H+)

• Presence of dilator substances produced by the endothelium (e.g. nitric oxide)

• Blood pressure change within the blood vessel

• Sympathetic activity leads to a reduced blood flow in active areas

How is blood volume affected by endurance exercise adaptations?

• Increase in plasma proteins (e.g. albumin) which helps retain fluid in the bloodstream

• Increase in total body water due to alterations in kidney function and reduced urination

How does the adaptations of blood volume improve CV performance?

Keep blood viscosity low, increasing venous return and therefore stroke volume