The Respiratory System Quiz

Cardiovascular Changes during Exercise

• The Fick equation for cardiac output is: CO = VO2 / (a-vO2)
• The activity that reviews cardiovascular changes during exercise is called exercise physiology
• The variable measured during recovery after exercise is called excess post-exercise oxygen consumption (EPOC)

Maximal Cardiac Output

• Maximal cardiac output is the highest rate at which the heart can pump blood to meet the oxygen demands of the body during exercise
• Maximal cardiac output is limited by the ability of the heart to pump blood, not by the ability of the lungs to take in oxygen
• The major purpose of the increase in cardiac output during exercise is to deliver oxygen and nutrients to the muscles

Cardiovascular Responses to Exercise

• The likely limitation of O2max is the ability of the cardiovascular system to deliver oxygen to the muscles
• A decrease in peripheral resistance is NOT a cardiovascular response to acute exercise
• The resting heart rate (RHR) for most individuals is between 60-100 beats per minute

Cardiovascular Adjustments during Exercise

• The primary goal of cardiovascular adjustments during dynamic exercise is to maintain adequate blood flow and oxygen delivery to the muscles
• Maximal heart rate (HRmax) is the highest heart rate achievable during exercise, and it decreases with age
• HRmax can be estimated using the equation: 220 - age

Stroke Volume and Exercise

• Stroke volume (SV) is primarily determined by preload, afterload, and contractility
• SV increases during exercise due to an increase in preload and contractility, and a decrease in afterload
• The upright position results in lower resting SV values compared to the supine position
• SV increases with exercise intensity up to approximately 40% to 60% of O2max, and then plateaus

Heart Rate and Exercise

• The steady-state heart rate is the heart rate achieved during prolonged exercise at a moderate intensity
• A lower steady-state heart rate at a fixed exercise intensity indicates a higher level of cardiovascular fitness
• Heart rate variability (HRV) is the variation in time between heartbeats

Factors Affecting Stroke Volume

• Factors that can contribute to an increase in SV during exercise include an increase in preload, contractility, and sympathetic nerve activity
• Factors that do not influence SV during acute exercise include changes in afterload
• The typical pattern of SV during exercise is an increase with exercise intensity up to approximately 40% to 60% of O2max, and then a plateau

Cardiac Output and Exercise

• The formula for calculating cardiac output (CO) is: CO = HR x SV
• Diagnostic techniques such as echocardiography and cardiac magnetic resonance imaging (MRI) have been used to determine how the heart chambers respond to increasing oxygen demands during exercise
• The Frank-Starling mechanism is a mechanism that increases stroke volume in response to an increase in preload
• The approximate increase in SV from rest to maximal exercise in active but untrained individuals is 20-40%