COMSAE PHASE 1 EXERCISE &
ENVIRONMENTAL PHYSIOLOGY PRACTICE
EXAM WITH ACTUAL QUESTIONS AND
VERIFIED ANSWERS, PLUS EXPLAINED
RATIONALES/EXPERT VERIFIED FOR
GUARANTEED 100% PASS 2026/LATEST
UPDATE/INSTANT DOWNLOAD PDF
1. A healthy 25-year-old man begins strenuous cycling. Within
several minutes, cardiac output increases substantially, skeletal
muscle blood flow rises, and blood flow to the gastrointestinal tract
decreases. Which mechanism most directly accounts for the
increased blood flow to exercising skeletal muscle?
A. Increased sympathetic α1-adrenergic stimulation of skeletal muscle
arterioles
B. Local accumulation of vasodilator metabolites in active skeletal
muscle
C. Increased parasympathetic stimulation of skeletal muscle arterioles
D. Increased circulating angiotensin II
E. Decreased arterial pressure causing passive arteriolar dilation
Answer: B. Local accumulation of vasodilator metabolites in active
skeletal muscle
Rationale: Active skeletal muscle produces metabolites such as
adenosine, K⁺, H⁺, CO₂, lactate, and inorganic phosphate that promote
local arteriolar vasodilation. This metabolic vasodilation can override
sympathetic vasoconstrictor influences during exercise. The result is a
major increase in skeletal-muscle perfusion proportional to metabolic
1
,demand. Sympathetic α1 stimulation generally promotes
vasoconstriction, while parasympathetic innervation is not responsible
for the major exercise-induced increase in skeletal-muscle blood flow.
2. A 30-year-old woman performs progressively harder treadmill
exercise. Her oxygen consumption rises from 250 mL/min at rest
to 2,500 mL/min during maximal exercise. Which variable is most
directly represented by this increase in oxygen consumption?
A. Cardiac oxygen consumption
B. Pulmonary oxygen diffusion capacity
C. Whole-body metabolic rate expressed as oxygen utilization
D. Oxygen content of venous blood
E. Alveolar ventilation
Answer: C. Whole-body metabolic rate expressed as oxygen
utilization
Rationale: VO₂ represents the rate at which the body consumes oxygen
and is therefore a major index of whole-body aerobic metabolic rate.
During exercise, increased ATP production by skeletal muscle requires
substantially increased oxidative phosphorylation, increasing oxygen
extraction from the blood and overall oxygen consumption. VO₂ is
determined by the Fick principle: VO₂ = cardiac output × (arterial O₂
content − venous O₂ content).
3. During maximal aerobic exercise, a trained athlete has a cardiac
output of 25 L/min, an arterial oxygen content of 200 mL O₂/L
blood, and a mixed venous oxygen content of 40 mL O₂/L blood.
What is the athlete's approximate oxygen consumption?
A. 1,000 mL/min
B. 2,000 mL/min
2
,C. 3,000 mL/min
D. 4,000 mL/min
E. 5,000 mL/min
Answer: E. 4,000 mL/min
Rationale: The Fick principle states VO₂ = cardiac output ×
arteriovenous oxygen difference. The arteriovenous difference is 200 −
40 = 160 mL/L. Therefore, VO₂ = 25 L/min × 160 mL/L = 4,000
mL/min. During maximal exercise, both cardiac output and peripheral
oxygen extraction increase substantially.
4. A previously sedentary individual begins an endurance-training
program. After several months, which cardiovascular adaptation is
most likely?
A. Decreased maximal stroke volume
B. Decreased blood volume
C. Increased resting heart rate
D. Increased maximal oxygen consumption
E. Decreased skeletal-muscle mitochondrial density
Answer: D. Increased maximal oxygen consumption
Rationale: Endurance training increases VO₂ max through central
and peripheral adaptations. These include increased plasma volume,
enhanced ventricular filling, increased stroke volume, improved
skeletal-muscle capillary density, greater mitochondrial content, and
improved oxidative enzyme activity. Resting heart rate generally
decreases because stroke volume and parasympathetic tone increase.
Blood volume generally increases rather than decreases.
5. A 22-year-old athlete develops a heart rate of 180/min during
intense exercise. Despite this tachycardia, cardiac output continues
3
, to increase. Which change most directly contributes to maintaining
cardiac output during exercise?
A. Markedly prolonged ventricular diastole
B. Increased venous return and enhanced myocardial contractility
C. Decreased sympathetic stimulation
D. Reduced end-diastolic volume
E. Decreased ventricular contractility
Answer: B. Increased venous return and enhanced myocardial
contractility
Rationale: Cardiac output equals heart rate × stroke volume. During
exercise, sympathetic activation increases myocardial contractility,
while skeletal-muscle and respiratory pumps increase venous return.
Increased venous return raises end-diastolic volume and therefore
stroke volume through the Frank-Starling mechanism. At extremely
high heart rates, diastolic filling time eventually becomes limiting, but
during most progressive exercise cardiac output still increases
substantially.
6. A runner abruptly stops after completing a long sprint. He becomes
lightheaded and nearly loses consciousness. Which physiological
change most likely contributes to this phenomenon?
A. Increased venous return caused by skeletal-muscle contraction
B. Persistent peripheral vasodilation combined with loss of the skeletal-
muscle pump
C. Increased cerebral perfusion caused by sympathetic activation
D. Increased systemic vascular resistance caused by metabolite
accumulation
E. Increased cardiac preload caused by abrupt cessation of exercise
4
ENVIRONMENTAL PHYSIOLOGY PRACTICE
EXAM WITH ACTUAL QUESTIONS AND
VERIFIED ANSWERS, PLUS EXPLAINED
RATIONALES/EXPERT VERIFIED FOR
GUARANTEED 100% PASS 2026/LATEST
UPDATE/INSTANT DOWNLOAD PDF
1. A healthy 25-year-old man begins strenuous cycling. Within
several minutes, cardiac output increases substantially, skeletal
muscle blood flow rises, and blood flow to the gastrointestinal tract
decreases. Which mechanism most directly accounts for the
increased blood flow to exercising skeletal muscle?
A. Increased sympathetic α1-adrenergic stimulation of skeletal muscle
arterioles
B. Local accumulation of vasodilator metabolites in active skeletal
muscle
C. Increased parasympathetic stimulation of skeletal muscle arterioles
D. Increased circulating angiotensin II
E. Decreased arterial pressure causing passive arteriolar dilation
Answer: B. Local accumulation of vasodilator metabolites in active
skeletal muscle
Rationale: Active skeletal muscle produces metabolites such as
adenosine, K⁺, H⁺, CO₂, lactate, and inorganic phosphate that promote
local arteriolar vasodilation. This metabolic vasodilation can override
sympathetic vasoconstrictor influences during exercise. The result is a
major increase in skeletal-muscle perfusion proportional to metabolic
1
,demand. Sympathetic α1 stimulation generally promotes
vasoconstriction, while parasympathetic innervation is not responsible
for the major exercise-induced increase in skeletal-muscle blood flow.
2. A 30-year-old woman performs progressively harder treadmill
exercise. Her oxygen consumption rises from 250 mL/min at rest
to 2,500 mL/min during maximal exercise. Which variable is most
directly represented by this increase in oxygen consumption?
A. Cardiac oxygen consumption
B. Pulmonary oxygen diffusion capacity
C. Whole-body metabolic rate expressed as oxygen utilization
D. Oxygen content of venous blood
E. Alveolar ventilation
Answer: C. Whole-body metabolic rate expressed as oxygen
utilization
Rationale: VO₂ represents the rate at which the body consumes oxygen
and is therefore a major index of whole-body aerobic metabolic rate.
During exercise, increased ATP production by skeletal muscle requires
substantially increased oxidative phosphorylation, increasing oxygen
extraction from the blood and overall oxygen consumption. VO₂ is
determined by the Fick principle: VO₂ = cardiac output × (arterial O₂
content − venous O₂ content).
3. During maximal aerobic exercise, a trained athlete has a cardiac
output of 25 L/min, an arterial oxygen content of 200 mL O₂/L
blood, and a mixed venous oxygen content of 40 mL O₂/L blood.
What is the athlete's approximate oxygen consumption?
A. 1,000 mL/min
B. 2,000 mL/min
2
,C. 3,000 mL/min
D. 4,000 mL/min
E. 5,000 mL/min
Answer: E. 4,000 mL/min
Rationale: The Fick principle states VO₂ = cardiac output ×
arteriovenous oxygen difference. The arteriovenous difference is 200 −
40 = 160 mL/L. Therefore, VO₂ = 25 L/min × 160 mL/L = 4,000
mL/min. During maximal exercise, both cardiac output and peripheral
oxygen extraction increase substantially.
4. A previously sedentary individual begins an endurance-training
program. After several months, which cardiovascular adaptation is
most likely?
A. Decreased maximal stroke volume
B. Decreased blood volume
C. Increased resting heart rate
D. Increased maximal oxygen consumption
E. Decreased skeletal-muscle mitochondrial density
Answer: D. Increased maximal oxygen consumption
Rationale: Endurance training increases VO₂ max through central
and peripheral adaptations. These include increased plasma volume,
enhanced ventricular filling, increased stroke volume, improved
skeletal-muscle capillary density, greater mitochondrial content, and
improved oxidative enzyme activity. Resting heart rate generally
decreases because stroke volume and parasympathetic tone increase.
Blood volume generally increases rather than decreases.
5. A 22-year-old athlete develops a heart rate of 180/min during
intense exercise. Despite this tachycardia, cardiac output continues
3
, to increase. Which change most directly contributes to maintaining
cardiac output during exercise?
A. Markedly prolonged ventricular diastole
B. Increased venous return and enhanced myocardial contractility
C. Decreased sympathetic stimulation
D. Reduced end-diastolic volume
E. Decreased ventricular contractility
Answer: B. Increased venous return and enhanced myocardial
contractility
Rationale: Cardiac output equals heart rate × stroke volume. During
exercise, sympathetic activation increases myocardial contractility,
while skeletal-muscle and respiratory pumps increase venous return.
Increased venous return raises end-diastolic volume and therefore
stroke volume through the Frank-Starling mechanism. At extremely
high heart rates, diastolic filling time eventually becomes limiting, but
during most progressive exercise cardiac output still increases
substantially.
6. A runner abruptly stops after completing a long sprint. He becomes
lightheaded and nearly loses consciousness. Which physiological
change most likely contributes to this phenomenon?
A. Increased venous return caused by skeletal-muscle contraction
B. Persistent peripheral vasodilation combined with loss of the skeletal-
muscle pump
C. Increased cerebral perfusion caused by sympathetic activation
D. Increased systemic vascular resistance caused by metabolite
accumulation
E. Increased cardiac preload caused by abrupt cessation of exercise
4
