1. Cardiovascular response to exercise

Acute Adaptations

Increase blood flow to muscles, reduce blood flow to low activity tissues

1. Increase o2 delivery to working muscles

2. Reduce delivery to e.g. intestines

Chronically Adaptations

More effective o2 delivery during sub-maximal exercise + increased maximum o2 consumption (VO2 Max)

1. Delivers more o2 to active muscles mass

Cardiovascular factors that influence O2 Uptake + VO2 Max

1. Cardiac strucutre and function

2. Blood (plasma) vol - widen heart

3. Blood flow/distribution - in active muscles

4. o2 Extraction - arterio venous difference

• Peripheral - what’s been taken up by the muscle

Cardiac Output 

The volume of blood pumped out the heart per minute 

Heart Rate x Stroke Volume

Stroke Volume

The volume of blood ejected out the left ventricle per beat

o2 Extraction: (a-v) o2 Difference

1. Training increases submaximal + maximal values in muscles

2. Active muscle - utilise o2 more efficiently

3. Increase oxidative capacity (higher oxidative enzyme content)

Physiological Cardiac Hypertrophy

enlarged heart (mass and size)

Heart Structure

Venous return

The volume of blood returning to the heart via the veins

Vascular resistance

the force that must overcome to push blood through the circulatory system

Preload

The amount of blood in the ventricle before contraction (end diastolic volume)

1. Determines cardiac muscle length before contraction

2. Determined by venous return

3. Increase CO + HR = Preload increase

4. Increase in moderate intensity

Afterload

The pressure against which the ventricle must contract (vascular resistance)

1. Higher the afterload, less blood ejected per heartbeat

2. Heart has limited force

3. Moderate intensity - can decrease, vessels open for o2

Ventricle valves during Systole and Diastole

Systole = contraction of heart (emptying)

Diastole = relaxation phase of heart (filling)

Contractility: The Frank-Starling Mechanism

Contractility = intrinsic ability of the heart muscle (myocardium) to generate force and to shorten during contraction, independent of how much it’s stretched (preload) or how much resistance it’s pumping against (afterload)

1. Principle based on length-tension relationship of ventricle

2. Greater stretch, greater contraction

3. Preload (end diastolic vol) increases, ventricular fiber length increases, increasing muscle tension

Athlete’s Heart: Potential Mechanisms

1. Left ventricular Mass - heavier in all athletes

2. Left ventricular Vol - larger in ENDURANCE athletes

• Increased CO stretches out heart

• Increased preload, Increases SV, Eccentric hypertrophy

3. Posterior wall/Septal thickness - larger in RESISTANCE

• Beefier

• Increased Afterload, Decreases SV, Concentric hypertrophy

• Work against high resistance, decreases SV

Endurance training adaptations: Stroke Volume

1. Increased preload (ventricular filling) = Increase ventricular dimensions

2. Increased diastolic filling time due to bradycardia

3. Bradycardia = slow HR

4. Increased contractility

5. Increased maximal SV

Endurance Training Adaptations: Heart Rate

1. Increased SV = Decreased HR for the same CO (sub-maximal exercise)

2. Max HR unchanged

Endurance Training Adaptations: Cardiac Output (Q)

Product of SV x HR

1. Most significant adaptation - major determinant of VO2 Max

2. Sub-Max Exercise = lower CO (increased o2 extraction)

3. Better muscle oxidative capacity - higher a-vO2 diff (more enzymes)

Acute Blood Redistribution

Acute Blood Flow Regulation

Muscle activity, pH go up

1. Muscle metabolites + Temp

2. Dilator substances produced by endothelium e.g. NO (open BV’s)

3. Pressure changes within vessels - myogenic

4. Symp Acticvity - reduce blood flow to low activity tissues (adrenalin receptors) 

Training the heart through increases in blood vol?

Primary Mechanisms for Blood Vol Increase:

1. Increase in plasma proteins - Albumin (Osmotic effect)

2. Increase in total body water - alterations in kidney function (Reduced urine output, Increased water retention)

Effects of Various Training Modalities on Blood Volume

1. Increased Haemoglobin = Increased VO2 Max

2. Strong relationship

Blood Volume Changes

March 2019, Nordic skiing: Blood doping scandal rocks sport as five athletes arrested

1. EPO = induces production of RBC

2. Blood Transfusions - blood doping

• Autologous - own blood

• Homologous - another person’s blood

Aerobic training adaptations overview: increasing oxygen delivery to muscle

Summary