Exercise Physiology — MCQs

Exercise Physiology Indian Medical PG Practice Questions and MCQs

Question 71: Which of the following is a characteristic feature of athletic heart syndrome?

A. Bradycardia
B. Normal QT interval
C. Increased U-waves
D. Increased left ventricular wall thickness (Correct Answer)

Explanation: ***Increased left ventricular wall thickness*** - **Physiological cardiac remodeling** in athletes often leads to an increase in **left ventricular muscle mass** and wall thickness in response to chronic exercise. - This adaptation allows the heart to pump more blood per beat, improving **cardiac efficiency** and **stroke volume**. *Bradycardia* - While **bradycardia** (a slower heart rate) is common in trained athletes, it is a consequence of increased **vagal tone** and enhanced stroke volume, not a defining characteristic of the morphological changes of athletic heart syndrome itself. - The syndrome primarily refers to the structural adaptations of the heart, like ventricular hypertrophy and chamber dilation. *Normal QT interval* - A **normal QT interval** is generally expected in athletic heart syndrome, whereas a **prolonged QT interval** is a sign of underlying pathology (e.g., long QT syndrome) and would raise concern for cardiac arrhythmias. - This is a feature indicating the benign nature of athletic heart and helps differentiate it from pathological conditions. *Increased U-waves* - **Prominent U-waves** on an electrocardiogram are more commonly associated with conditions like **hypokalemia** or certain antiarrhythmic drugs, not typically with athletic heart syndrome. - While some ECG changes can occur, increased U-waves are not a characteristic finding specifically linked to this physiological adaptation.

Question 72: During moderately intense isotonic exercise, all of the following increase except:

A. Respiratory rate
B. Total Peripheral resistance (Correct Answer)
C. Heart rate
D. Mean arterial pressure

Explanation: ***Total Peripheral resistance*** - During isotonic exercise, **vasodilation** in working muscles leads to a decrease in **total peripheral resistance** to facilitate increased blood flow and oxygen delivery. - While some vascular beds constrict, the overwhelming effect of vasodilation in active muscles causes a net decrease in overall resistance. *Mean arterial pressure* - **Mean arterial pressure** typically increases during isotonic exercise due to a significant rise in **cardiac output** that outweighs the decrease in total peripheral resistance. - This increase helps maintain adequate perfusion pressure to active muscles and other vital organs. *Heart rate* - **Heart rate** increases proportionally with exercise intensity during isotonic exercise to meet the increased metabolic demands of the working muscles. - This is a primary mechanism to boost **cardiac output** and oxygen transport. *Respiratory rate* - **Respiratory rate** increases during isotonic exercise to enhance **gas exchange**, removing CO2 and taking in more O2 to support the heightened metabolic activity. - This response is driven by the body's need to maintain **acid-base balance** and provide sufficient oxygen to tissues.

Question 73: The maximum allowable sweat rate during intense physical exercise for a healthy adult is approximately:

A. 21 ltrs
B. 2.5 ltrs (Correct Answer)
C. 3.5 ltrs
D. 4.5 ltrs

Explanation: ***2.5 ltrs*** - A healthy adult's body can typically **cool itself effectively** through sweating up to an average rate of **2.5 liters per hour** during intense physical exercise. - This rate balances **effective thermoregulation** with the body's capacity to replenish fluids and electrolytes to maintain **homeostasis**. *3.5 ltrs* - While individuals can sweat at rates exceeding 2.5 L/hr, consistently higher rates like **3.5 L/hr** over prolonged periods of intense exercise would put a significant strain on the body's **fluid balance** and electrolyte regulation, increasing the risk of **dehydration** and heat-related illness. - Such rates are often seen in **elite athletes** under extreme conditions and are not a sustainable maximum for general healthy adults. *21 ltrs* - A sweat rate of **21 liters per hour** is physiologically impossible and would lead to immediate, severe, and life-threatening **dehydration**. - The human body simply cannot produce sweat at this volume nor could it sustain such a rapid fluid loss. *4.5 ltrs* - Sweating at **4.5 liters per hour** is an extremely high rate that would be difficult to sustain and would rapidly lead to **severe dehydration** and **electrolyte imbalances** in virtually any individual. - This rate is far beyond what the body can safely manage during prolonged intense exercise without rapid and aggressive fluid replenishment.

Question 74: During a maximal exercise test, which of the following best describes the likely changes in his muscle oxygen extraction and arteriovenous oxygen difference (a-vO2 diff)?

A. Decreased muscle oxygen extraction and decreased a-vO2 diff
B. Increased muscle oxygen extraction and increased a-vO2 diff (Correct Answer)
C. Increased muscle oxygen extraction and decreased a-vO2 diff
D. Decreased muscle oxygen extraction and increased a-vO2 diff

Explanation: ***Increased muscle oxygen extraction and increased a-vO2 diff*** - During **maximal exercise**, skeletal muscles have a significantly **higher metabolic demand** for oxygen to produce ATP. - This increased demand leads to greater **oxygen extraction** from the blood by the muscles, resulting in a larger difference between the arterial and venous oxygen content (**a-vO2 diff**). *Decreased muscle oxygen extraction and decreased a-vO2 diff* - This scenario would imply a **reduced oxygen utilization** by the muscles and a smaller difference in oxygen content, which is contrary to the body's physiological response during intense exercise. - Such a decrease would lead to rapid **fatigue** and an inability to sustain high-intensity activity due to insufficient energy production. *Increased muscle oxygen extraction and decreased a-vO2 diff* - An increase in muscle oxygen extraction is correct, but a **decreased a-vO2 diff** is contradictory. If more oxygen is extracted, the venous oxygen content would be lower, thereby increasing the a-vO2 diff. - A decreased a-vO2 diff alongside increased extraction would suggest an unphysiologic process or an error in understanding the relationship between these two variables. *Decreased muscle oxygen extraction and increased a-vO2 diff* - This option presents a contradiction: a **decreased muscle oxygen extraction** would logically lead to a *smaller* a-vO2 diff, as less oxygen is being removed from the blood. - An increased a-vO2 diff would only occur with *increased* oxygen extraction by the tissues.

Practice by Chapter

Energy Systems in Exercise

Practice Questions

Cardiovascular Responses to Exercise

Practice Questions

Respiratory Adaptations to Exercise

Practice Questions

Muscle Metabolism During Exercise

Practice Questions

Neuromuscular Adaptations to Training

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Exercise in Hot and Cold Environments

Practice Questions

Fatigue Mechanisms

Practice Questions

Recovery Processes

Practice Questions

Training Principles and Adaptations

Practice Questions

Exercise Testing and Prescription

Practice Questions

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