Cardiovascular Physiology During Exercise Quiz

Energy Expenditure and Oxygen Uptake

• Total energy expenditure does not include thermic effect of food.
• Oxygen uptake can be calculated using the Fick equation: VO2 = ( cardiac output x arterio-venous oxygen difference ).

Measurement of Human Work Output and Power

• Methods used to measure human work output and power include Oxygen uptake, Blood lactate, and Heart rate, but not Electromyography (EMG).

Energy Expenditure and Kcal

• Energy expenditure can be expressed in terms of kcal by multiplying oxygen uptake (in liters) by the caloric equivalent of oxygen (approximately 4.8 kcal/L).

Work Rate and Maximal Oxygen Uptake (VO2max)

• Work rate and VO2max are highly correlated in subjects with different levels of physical conditioning.

Cardiac Output and Blood Flow Regulation

• During exercise, approximately 80% of cardiac output is directed towards working skeletal muscle.
• Nitric oxide plays a crucial role in blood flow regulation during exercise by causing vasodilation.

Aortic Blood Pressure and Stroke Volume

• Average aortic blood pressure is approximately 100 mmHg.
• Aortic blood pressure and stroke volume are directly related.

Sympathetic Stimulation and Stroke Volume

• Sympathetic stimulation increases stroke volume.

Exercise and Stroke Volume

• In untrained subjects, stroke volume reaches a plateau at approximately 40-50% of VO2max during exercise.

Myocardial Oxygen Demand

• The three main determinants of myocardial oxygen demand that increase during exercise are Heart rate, Contractility, and Preload.

Cardiac Output, Oxygen Consumption, and Arterial-Venous Oxygen Difference

• The relationship between cardiac output (Q), arterial-venous oxygen difference (a-vO2 difference), and oxygen consumption (VO2) can be described by the equation: VO2 = Q x (a-vO2 difference).

Exercise and Venous Hemoglobin Saturation

• During exercise, as exercise intensity increases, venous hemoglobin saturation of blood decreases.

Double Product (Rate-Pressure Product)

• The equation for calculating the double product (rate-pressure product) during exercise is: Rate-Pressure Product = Heart rate x Systolic blood pressure.

Incremental Exercise and Cardiovascular Responses

• During incremental exercise, cardiac output, heart rate, and stroke volume all increase.

Redistribution of Blood Flow

• During exercise, blood flow is redistributed from viscera and skin to working skeletal muscle.
• Blood flow is redistributed in a pattern of increased blood flow to active muscles and decreased blood flow to inactive areas.

Regulation of Local Blood Flow

• Local blood flow during exercise is regulated by Vasodilation, Vasopressin, and Baroreceptors.

Hemodynamic Differences between Upper and Lower Limb Exercise

• Upper limb exercise results in higher heart rates and lower cardiac outputs compared to lower limb exercise.

Cardiovascular Responses to Prolonged Exercise

• Cardiovascular responses to prolonged exercise include increased cardiac output, heart rate, and stroke volume.

Arm Work and Heart Rate

• During arm work, the main reason for the higher heart rate compared to leg work is the smaller muscle mass of the arms.

Formulas for Cardiovascular Parameters

• The formula for calculating stroke volume (SV) is: SV = End-diastolic volume - End-systolic volume.
• The formula for calculating cardiac output (Q) is: Q = Heart rate x Stroke volume.
• The formula for calculating ejection fraction (EF) is: EF = (Stroke volume / End-diastolic volume) x 100%.
• The formula for calculating VO2max is: VO2max = (Cardiac output x Arterial-venous oxygen difference) / Body weight.

Athlete's Heart

• A stimulus for cardiac chamber enlargement in athletes' heart is Chronic volume overload.
• Changes in left and right ventricular morphology can be seen as early as 3 months in athletes' heart, including increased left ventricular wall thickness and chamber size.

Physiologic Adaptation to Chronic Exercise Training

• What distinguishes the physiologic adaptation to chronic exercise training from pathologic conditions associated with cardiac hypertrophy is the absence of fibrosis and preserved cardiac function.

Detraining and VO2max

• During detraining, VO2max decreases.

Detraining and Oxidative Capacity of Muscle

• During detraining, the oxidative capacity of muscle decreases.