ACSM Exercise Physiology 3 — Questions and Answers
Question 1: The Fick equation for VO2 is best expressed as:
- VO2 = HR × SV × (CaO2 – CvO2) (Correct answer)
- VO2 = HR × SV / (CaO2 + CvO2)
- VO2 = MAP × TPR × (CaO2 – CvO2)
- VO2 = VE × FiO2 – FEO2
Correct answer: VO2 = HR × SV × (CaO2 – CvO2)
The Fick principle states that VO2 equals cardiac output (HR × SV) multiplied by the arteriovenous oxygen difference (a-vO2 diff).
Question 2: During maximal aerobic exercise, what is the primary limiting factor for VO2max in most healthy untrained individuals?
- Pulmonary diffusion capacity
- Mitochondrial enzyme activity
- Cardiac output (oxygen delivery) (Correct answer)
- Skeletal muscle capillary density
Correct answer: Cardiac output (oxygen delivery)
In untrained individuals, maximal cardiac output is the primary limiter of VO2max because it constrains oxygen delivery to working muscles.
Question 3: Which physiological adaptation primarily explains the reduction in resting heart rate seen after 12 weeks of aerobic training?
- Decreased parasympathetic tone
- Increased intrinsic heart rate
- Enhanced stroke volume allowing lower HR for the same cardiac output (Correct answer)
- Reduced total blood volume
Correct answer: Enhanced stroke volume allowing lower HR for the same cardiac output
Training increases stroke volume (via cardiac hypertrophy and increased blood volume), so a lower resting heart rate maintains the required cardiac output.
Question 4: What is the primary fuel source during low-intensity exercise at 25% of VO2max?
- Muscle glycogen
- Blood glucose
- Plasma free fatty acids (Correct answer)
- Intramuscular triglycerides
Correct answer: Plasma free fatty acids
At very low exercise intensities, plasma free fatty acids from adipose tissue lipolysis are the dominant energy substrate.
Question 5: The ventilatory threshold (VT) is identified during a graded exercise test by noting a nonlinear increase in:
- VCO2 relative to VO2 (Correct answer)
- Heart rate relative to workload
- Blood pressure relative to heart rate
- VO2 relative to workload
Correct answer: VCO2 relative to VO2
VT is detected by a disproportionate rise in VCO2 relative to VO2 (the V-slope method), reflecting buffering of excess lactate by bicarbonate.
Question 6: Which of the following best describes the role of myoglobin in exercising skeletal muscle?
- It synthesizes ATP during high-intensity exercise
- It stores and facilitates intracellular oxygen transport to mitochondria (Correct answer)
- It increases calcium release from the sarcoplasmic reticulum
- It buffers hydrogen ions produced during glycolysis
Correct answer: It stores and facilitates intracellular oxygen transport to mitochondria
Myoglobin stores oxygen within muscle cells and facilitates its diffusion from the sarcolemma to mitochondria during exercise.
Question 7: Hyperthermia during prolonged exercise in the heat impairs performance primarily by:
- Decreasing plasma epinephrine
- Competing blood flow demands between skin and active muscles reducing muscle oxygen delivery (Correct answer)
- Increasing muscle glycogen utilization rate by 50%
- Directly inhibiting myosin ATPase activity
Correct answer: Competing blood flow demands between skin and active muscles reducing muscle oxygen delivery
Heat stress causes vasodilation in the skin for cooling while muscles need blood flow, creating competition that reduces muscle perfusion and VO2.
ACSM Exercise Physiology 3
The Fick equation for VO2 is best expressed as: