Exercise Physiology Test 2 Chapter 4

What is the main purpose of cardiovascular responses during acute exercise?

To increase blood flow and oxygen delivery to working muscles so they can meet their increased metabolic demands.

What are the major cardiovascular responses to acute exercise?

Increased heart rate (HR), stroke volume (SV), cardiac output (Q), blood pressure, and blood flow to working muscles.

What is resting heart rate (RHR)?

The number of times the heart beats per minute while the body is at rest.

What is the normal untrained resting heart rate?

Generally 60–100 beats per minute.

What can the resting heart rate of trained athletes be?

As low as 30–40 beats per minute.

What affects resting heart rate?

Autonomic nervous system innervation, including sympathetic and parasympathetic activity.

What is an anticipatory heart rate response?

Heart rate increases above resting levels just before exercise begins.

Why does heart rate increase before exercise?

Parasympathetic (vagal) tone decreases and sympathetic activity and catecholamines increase.

What happens to vagal tone before exercise?

It decreases, allowing heart rate to rise.

What are norepinephrine and epinephrine?

Catecholamines that increase sympathetic stimulation and help raise heart rate during exercise.

What is steady-state heart rate?

The point at which heart rate reaches a plateau and meets the circulatory demands of a constant submaximal exercise intensity.

What happens to steady-state heart rate when exercise intensity increases?

Steady-state heart rate increases to meet the greater metabolic demands.

How long does heart rate take to adjust to a new exercise intensity?

Usually a few minutes; the exact adjustment time depends on the exercise conditions.

Why is steady-state heart rate useful?

It is used in simple exercise tests to estimate aerobic fitness and maximum heart rate.

How is heart rate related to exercise intensity?

Heart rate is directly proportional to exercise intensity: as intensity increases, heart rate generally increases.

What is maximum heart rate (HRmax)?

The highest heart rate achieved during an all-out effort to voluntary exhaustion.

How does maximum heart rate change with age?

It generally declines slightly with age.

What is the estimated maximum heart rate equation?

HRmax = 220 − age in years.

Is the 220 − age equation an exact measurement?

No. It is an estimate; actual maximum heart rate varies between individuals.

What is the relationship between heart rate and oxygen consumption (VO2)?

As exercise intensity and oxygen consumption increase, heart rate generally increases.

What is stroke volume (SV)?

The amount of blood pumped out of the left ventricle with each heartbeat.

How does stroke volume respond to increasing exercise intensity?

It increases as intensity increases, up to approximately 40–50% of VO2max in many individuals, then often plateaus.

What happens to stroke volume after it reaches a plateau during exercise?

It generally remains relatively stable through exhaustion.

What is a possible exception to the stroke volume plateau?

Elite endurance athletes may continue increasing stroke volume at higher exercise intensities.

How does maximal-exercise stroke volume compare with standing resting stroke volume?

It is approximately double standing stroke volume.

How does maximal-exercise stroke volume compare with supine resting stroke volume?

It is only slightly higher than supine resting stroke volume.

Why is stroke volume higher when lying supine than when standing?

Lying down increases venous return and ventricular filling.

What is cardiac output (Q)?

The amount of blood pumped by the heart per minute.

What is the cardiac output equation?

Q = HR × SV.

What happens to cardiac output during exercise?

It increases because heart rate and stroke volume generally increase.

What is left ventricular compliance?

The ability of the left ventricle to relax and stretch to fill with blood.

How does endurance training affect left ventricular compliance?

It improves the heart's ability to fill with blood during diastole.

What is eccentric hypertrophy?

An increase in the size of the heart's ventricular chamber, commonly associated with endurance training.

What is enhanced myocardial compliance?

The trained heart muscle becomes better able to relax and stretch during filling.

Why is faster active relaxation beneficial?

It allows the ventricle to fill more effectively, especially when heart rate is high.

What is the Frank-Starling mechanism?

Increased end-diastolic volume stretches myocardial fibers, resulting in a more forceful contraction and increased stroke volume.

What is end-diastolic volume (EDV)?

The amount of blood in the ventricle at the end of filling, just before contraction.

How does increased EDV affect stroke volume?

It stretches the heart muscle fibers more, producing a stronger contraction and increasing stroke volume.

What is hypervolemia?

An expansion of total blood volume.

How much can total blood and plasma volume expand in elite endurance athletes?

Approximately 10–20% or more.

How does increased blood volume help endurance athletes?

It supports venous return, ventricular filling, preload, and stroke volume during heavy exercise.

What is venous return?

The flow of blood returning to the heart.

What is preload?

The degree of ventricular filling and stretch before contraction.

What is the Fick Principle?

A principle used to calculate tissue oxygen consumption based on blood flow and the difference in oxygen content between arterial and venous blood.

What is the Fick equation?

VO2 = Q × (a-vO2 difference).

What does a-vO2 difference mean?

The difference in oxygen content between arterial blood and venous blood; it reflects how much oxygen tissues extract.

Why must blood flow be redistributed during exercise?

Working muscles need more oxygen and nutrients, so blood flow must shift toward tissues with the greatest metabolic demand.

What happens to cardiac output during exercise?

It increases, providing more blood flow that can be distributed throughout the body.

What is blood flow redistribution?

The process of directing more blood toward active muscles and away from less-active organs.

What is sympathetic vasoconstriction?

Narrowing of blood vessels due to sympathetic nervous system activity, which reduces blood flow to certain regions.

Which areas receive less blood flow during exercise because of sympathetic vasoconstriction?

Less-active regions, including the splanchnic circulation (liver, pancreas, and gastrointestinal organs) and kidneys.

What is local vasodilation?

The widening of blood vessels in response to local signals, increasing blood flow to an area.

What triggers local vasodilation in exercising muscles?

Metabolic and endothelial products released during exercise.

What is sympatholysis?

The local reduction or inhibition of sympathetic vasoconstriction, allowing blood vessels in active muscle to remain dilated.

Why is sympatholysis important during exercise?

It allows active muscles to receive more blood despite increased sympathetic nervous system activity.

What happens to skin blood flow as body temperature rises?

Skin blood flow increases to help release heat.

How does the body increase skin blood flow?

Sympathetic vasoconstriction decreases and vasodilation increases, allowing more blood to reach the skin.

What is cardiovascular drift?

A gradual increase in heart rate and decrease in stroke volume during prolonged exercise, often associated with increased core temperature and dehydration.

What happens to stroke volume during cardiovascular drift?

It gradually decreases.

Why does plasma volume decrease during prolonged exercise?

Fluid is lost through sweating and shifts out of the blood vessels.

What happens to skin blood flow during cardiovascular drift?

It increases to help dissipate heat.

How does cardiovascular drift affect venous return?

Venous return and preload decrease, contributing to reduced stroke volume.

What happens to heart rate during cardiovascular drift?

Heart rate gradually increases to compensate for the decreasing stroke volume and help maintain cardiac output.

What happens to cardiac output during cardiovascular drift?

It is generally maintained as heart rate rises to compensate for the decline in stroke volume.

What is the Valsalva maneuver?

A maneuver in which a person closes the glottis and bears down while contracting respiratory muscles.

What happens during the Valsalva maneuver?

The glottis closes, increasing intra-abdominal and intrathoracic pressure.

Why can the Valsalva maneuver be dangerous during exercise?

High internal pressures can compress major veins, reducing venous return, cardiac output, and arterial blood pressure.

What happens to venous return during a strong Valsalva maneuver?

It decreases.

What happens to cardiac output during a strong Valsalva maneuver?

It can decrease because less blood returns to the heart.

What is hemoconcentration?

An increase in the concentration of blood components because plasma volume decreases.

What happens to blood pH during high-intensity exercise above the anaerobic threshold?

Systemic arterial blood pH decreases.

Why does blood pH decrease during high-intensity exercise?

Hydrogen ion accumulation associated with high rates of anaerobic metabolism can exceed the blood's buffering capacity.

What are buffer systems?

Systems that help resist changes in pH by accepting or releasing hydrogen ions.

What is hematocrit (Hct)?

The percentage of blood volume made up of red blood cells.

What happens to hematocrit during exercise-induced hemoconcentration?

It increases because plasma volume decreases.

What happens to hemoglobin concentration during exercise-induced hemoconcentration?

It increases because there is less plasma relative to the blood cells.

What happens to red blood cell concentration during exercise-induced hemoconcentration?

It increases relative to the reduced plasma volume.

Why does fluid move out of blood vessels and into muscle tissue during exercise?

Increased capillary hydrostatic pressure and accumulated metabolic byproducts increase fluid movement into the interstitial space.

What is an additional cause of plasma volume loss during exercise?

Sweating.

What is sports pseudoanemia?

A condition in which trained athletes have slightly lower-than-normal baseline hematocrit and hemoglobin measurements because plasma volume has expanded.

Why does sports pseudoanemia occur?

Plasma volume expands faster and to a greater extent than red blood cell volume.

Is sports pseudoanemia the same as actual anemia?

No. It is a dilutional effect caused by expanded plasma volume, not necessarily a lack of red blood cells.

What is ventilation?

The movement of air into and out of the lungs.

What happens to ventilation when exercise begins?

It increases immediately.

Why does ventilation increase before muscle contractions begin?

An anticipatory response called central command prepares the respiratory system for exercise.

What is central command?

A signal from the brain that anticipates exercise and increases ventilation before the muscles begin working.

What causes the second, gradual phase of increased ventilation?

Chemical changes in arterial blood, especially increases in carbon dioxide and hydrogen ions.

What detects changes in carbon dioxide and hydrogen ions?

Chemoreceptors.

What are chemoreceptors?

Sensors that detect chemical changes, including changes in carbon dioxide and hydrogen ion levels, helping regulate breathing.

What is the relationship between ventilation and muscle metabolic needs?

Ventilation increases in proportion to the metabolic demands of working muscles.

What is tidal volume?

The amount of air inhaled or exhaled during one normal breath.

What happens to tidal volume at low exercise intensities?

Tidal volume increases, while breathing rate may change relatively little.

What happens to breathing rate and depth at high exercise intensities?

Both breathing rate and depth increase.

What happens to ventilation immediately after exercise stops?

It does not immediately return to resting levels; recovery is delayed.

How long can ventilation recovery take after exercise?

Several minutes.

What factors may regulate ventilation recovery?

Blood pH, partial pressure of carbon dioxide (PCO2), and body temperature.

What does ventilation match during exercise?

Metabolic rate and the body's changing oxygen and carbon dioxide demands.

What is the ventilatory equivalent for oxygen?

The ratio VE/VO2, representing liters of air breathed per liter of oxygen consumed per minute.

What does VE/VO2 measure?

How well breathing is matched to the body's oxygen demands.

What is ventilatory threshold?

The point during increasing exercise intensity when ventilation increases disproportionately compared with oxygen consumption.