Exercise Physiology — MCQs

Exercise Physiology Indian Medical PG Practice Questions and MCQs

Question 41: Daily water loss in sweat during high physical activities is approximately:

A. 200-400ml
B. 1000-1200ml (Correct Answer)
C. 50-100ml
D. 500-700ml

Explanation: ***1000-1200ml*** - During **high physical activities**, the body significantly increases **sweat production** to regulate body temperature. - This level of activity can lead to a substantial daily water loss through sweat, typically in the range of 1 to 1.2 liters (1000-1200 ml). *200-400ml* - This range represents a relatively **low level of sweat loss**, which might occur during mild activity or in cooler environments. - It seriously underestimates the water loss during **high physical activities**, where metabolic heat production is much greater. *50-100ml* - This amount is typical for **insensible water loss** through the skin in a sedentary state, not related to active sweating. - It is far too low for any physical activity, let alone **high physical activity**, which demands significant thermoregulation. *500-700ml* - This range might be closer to sweat loss during **moderate physical activity** or in less demanding conditions. - However, for **high physical activities**, especially those sustained over time, this amount is generally an underestimate of the total water loss.

Question 42: Aerobic capacity is increased by:

A. Strenuous exercise
B. Regular moderate-intensity exercise
C. High-intensity interval training (Correct Answer)
D. Prolonged exercise routine

Explanation: ***High-intensity interval training*** - **High-intensity interval training (HIIT)** is the **most efficient method** for improving **aerobic capacity (VO2max)** in the shortest time frame. - The alternating periods of maximal effort and short recovery lead to **greater increases in maximum oxygen uptake (VO2max)** compared to continuous moderate-intensity training. - HIIT elicits strong physiological adaptations in both **cardiovascular and muscular systems**, including increased mitochondrial density and enhanced oxygen delivery. *Strenuous exercise* - While strenuous exercise can contribute to improved fitness, it is a **broad, non-specific term** that does not refer to a structured training method optimized for aerobic capacity. - The effectiveness depends entirely on the **duration, frequency, intensity**, and specific structure of the exercise. *Regular moderate-intensity exercise* - **Regular moderate-intensity exercise** (continuous aerobic training) effectively improves aerobic capacity and is excellent for building an **endurance base**. - However, research shows that HIIT produces **faster and greater improvements in VO2max** per unit of training time compared to traditional moderate-intensity continuous training. - Both methods improve aerobic capacity, but HIIT is more **time-efficient** and produces superior VO2max adaptations. *Prolonged exercise routine* - A **prolonged exercise routine** is too vague and could refer to any long-duration training program. - While prolonged endurance training improves aerobic fitness, it is **less efficient** than HIIT for maximizing VO2max gains, though it excels at improving **fat oxidation** and **endurance performance**.

Question 43: During a 100 m sprint which of the following is used by the muscle for meeting energy demands?

A. Phosphofructokinase
B. Phosphocreatine (Correct Answer)
C. Glucose 1 - phosphate
D. Creatine phosphokinase

Explanation: ***Phosphocreatine*** - **Phosphocreatine (PCr)** is the primary energy source for a **100m sprint** (lasting 10-20 seconds). - The **ATP-PC (phosphagen) system** provides **immediate energy** by rapidly regenerating **ATP** from ADP through the transfer of a high-energy phosphate group. - This system is crucial for **short bursts of maximal intensity exercise** where energy demand exceeds the capacity of glycolysis and oxidative phosphorylation to respond quickly enough. - Phosphocreatine stores can fuel maximum effort for approximately **10-15 seconds**, making it ideal for sprint activities. *Phosphofructokinase* - **Phosphofructokinase (PFK)** is a key regulatory enzyme in **glycolysis**, not an energy substrate. - While PFK-catalyzed glycolysis contributes ATP during intense exercise, it cannot provide energy as rapidly as the phosphocreatine system. - Glycolysis becomes more prominent after the first 10-15 seconds of maximal effort. *Glucose 1-phosphate* - **Glucose 1-phosphate** is an intermediate in **glycogenolysis** (breakdown of glycogen to glucose-6-phosphate). - It is part of the pathway leading to glucose availability for glycolysis, but is not a **direct, immediate energy source** for muscle contraction. - Unlike phosphocreatine, it cannot directly regenerate ATP. *Creatine phosphokinase* - **Creatine phosphokinase (CPK)**, also known as **creatine kinase (CK)**, is the **enzyme** that catalyzes the reversible transfer of phosphate from phosphocreatine to ADP. - It facilitates the energy transfer reaction but is **not an energy substrate** itself. - The enzyme enables the phosphocreatine system to function, but the actual energy comes from phosphocreatine.

Question 44: The main cause of increased blood flow to exercising muscles is :

A. Increased sympathetic discharge to peripheral vessels
B. Vasodilatation due to local metabolites (Correct Answer)
C. Raised blood pressure
D. Increased heart rate

Explanation: ***Vasodilatation due to local metabolites*** - During exercise, muscles produce various **metabolites** such as **adenosine**, **lactate**, **potassium ions**, and **carbon dioxide**, which directly cause local vasodilatation. - This **metabolite-induced vasodilation** is the primary mechanism for increased blood flow to active muscles, ensuring adequate oxygen and nutrient supply. *Increased sympathetic discharge to peripheral vessels* - **Sympathetic stimulation** generally causes **vasoconstriction** in many peripheral vascular beds to redirect blood flow away from non-essential organs. - While sympathetic activity increases during exercise, its direct effect on skeletal muscle arterioles via beta-2 adrenergic receptors is vasodilatory, but this is overridden and localized by **metabolic autoregulation**. *Raised blood pressure* - While **blood pressure** does increase during exercise, it is a consequence of increased cardiac output and does not directly cause the specific **vasodilatation** within the exercising muscles. - A higher systemic blood pressure helps maintain perfusion against the dilated vascular beds, but the localized increase in flow is primarily due to local factors. *Increased heart rate* - An **increased heart rate** contributes to a higher **cardiac output**, ensuring more blood is available for distribution throughout the body, including to exercising muscles. - However, an elevated heart rate alone does not explain the selective increase in blood flow to active muscle beds; that specificity is due to **local vasodilatory mechanisms**.

Question 45: During exercise, blood flow to brain is

A. Increased
B. Decreased
C. Redirected to muscles
D. Remains unchanged (Correct Answer)

Explanation: ***Remains unchanged*** - **Cerebral blood flow** is remarkably well-regulated through **autoregulation** to ensure a constant supply of oxygen and nutrients to the brain. - During exercise, while blood flow redistributes to working muscles, the brain's supply remains stable due to its critical need for continuous perfusion. - The brain maintains a relatively constant blood flow of approximately 50-60 mL/100g/min regardless of exercise intensity within physiological limits. *Increased* - While other organs may experience increased blood flow during exercise, the **brain's blood flow** is maintained at a relatively constant level due to protective autoregulatory mechanisms. - Significant increases in cerebral blood flow are usually associated with conditions like hypercapnia or certain neurological events, not normal exercise. *Decreased* - A decrease in **cerebral blood flow** during exercise would be detrimental to brain function and is prevented by the brain's robust autoregulatory capacity. - Decreased cerebral blood flow can lead to symptoms like dizziness or lightheadedness, which are not typical responses to normal exercise. *Redirected to muscles* - While blood is **redirected to working muscles** during exercise, this redirection occurs from other vascular beds (e.g., splanchnic circulation, kidneys) to ensure adequate supply to the muscles, without compromising the brain. - The brain prioritizes its own blood supply through **autoregulation**, ensuring it remains unaffected by the shunting of blood to other tissues.

Question 46: All of the following are features of exercise EXCEPT:

A. Increased blood supply to muscles
B. Increased O₂ extraction
C. Increased stroke volume
D. Left shift of Hb-O₂ dissociation curve (Correct Answer)

Explanation: ***Left shift of Hb-O₂ dissociation curve*** - During exercise, **tissue metabolism** increases, leading to higher levels of **CO₂, H⁺, and 2,3-BPG**, and higher temperature which all cause a **right shift** of the Hb-O₂ dissociation curve. - A **right shift** signifies decreased hemoglobin affinity for oxygen, facilitating **oxygen unloading** to metabolically active tissues. *Increased blood supply to muscles* - Exercise drastically increases the **metabolic demands** of skeletal muscles, requiring a greater supply of **oxygen and nutrients**. - This is achieved through **vasodilation** in the active muscles and redistribution of blood flow. *Increased O₂ extraction* - As muscles work harder during exercise, their demand for oxygen increases, leading to a higher **arteriovenous oxygen difference**. - This means that a greater percentage of the oxygen delivered to the muscle is **extracted and utilized** by the tissues. *Increased stroke volume* - The **heart pumps more blood** with each beat to meet the increased circulatory demands of exercise. - This is a key mechanism for increasing **cardiac output** during physical activity.

Question 47: Aerobic capacity is increased by:

A. Strenuous exercise
B. Spurt of exercise
C. Prolonged exercise routine (Correct Answer)
D. Regular 3-minute exercise

Explanation: ***Prolonged exercise routine*** - **Aerobic capacity** (VO2 max) reflects the maximum rate at which the body can use oxygen during exercise. A **prolonged exercise routine** is the best answer because it emphasizes both **consistency** and **sustained duration** of cardiovascular activity. - This type of training leads to adaptations like increased **mitochondrial density**, enhanced **cardiac output**, improved **stroke volume**, and better oxygen extraction by tissues, all contributing to improved aerobic fitness. - Regular aerobic training (typically 20-60 minutes per session, 3-5 times weekly) produces the most reliable improvements in VO2 max. *Strenuous exercise* - While **regular strenuous exercise** can indeed improve aerobic capacity, this option lacks the qualifier "routine" or "regular," making it ambiguous. - Without consistency indicated, this could imply sporadic or single bouts of strenuous activity, which are insufficient for sustained improvements in **aerobic capacity**. - The best answer requires both adequate intensity AND regularity, which "prolonged exercise routine" better captures. *Spurt of exercise* - A "spurt of exercise" implies brief, high-intensity bursts of activity. While **HIIT** (high-intensity interval training) can improve aerobic capacity, isolated spurts without a structured routine are insufficient. - This type of activity primarily emphasizes the **anaerobic system** or short-term power rather than sustained cardiovascular adaptations. - Effective aerobic training requires consistent cardiovascular loading over time. *Regular 3-minute exercise* - While **"regular"** indicates consistency, **three minutes** is typically too short a duration to elicit significant cardiovascular adaptations needed to increase **aerobic capacity**. - To improve aerobic capacity, exercise sessions generally need to be longer (typically 20-60 minutes for continuous training) to adequately challenge the cardiovascular system and promote adaptations. - Brief regular sessions may maintain basic fitness but won't substantially increase VO2 max.

Question 48: In severe exercise, decrease in pH is due to:

A. Respiratory acidosis
B. H+ retention
C. HCO3 excretion
D. Lactic acidosis (Correct Answer)

Explanation: ***Lactic acidosis*** - During **severe exercise**, particularly anaerobic activity, muscles produce **lactic acid** secondary to **anaerobic glycolysis**. - **Lactic acid** dissociates into **lactate** and **hydrogen ions (H+)**, leading to an increase in H+ concentration and a decrease in pH. *Respiratory acidosis* - **Respiratory acidosis** results from **hypoventilation**, leading to CO2 retention and an increase in carbonic acid, which lowers pH. - During severe exercise, individuals typically **hyperventilate** to increase oxygen intake and expel CO2, thus preventing respiratory acidosis. *H+ retention* - **H+ retention** would imply that the body is failing to excrete hydrogen ions. While an accumulation of H+ ions does occur, it's primarily due to their overproduction (e.g., from lactic acid) rather than a simple failure of excretion mechanisms at the systemic level during exercise. - The mechanism is direct production, not just failure to excrete. *HCO3 excretion* - **Bicarbonate (HCO3-)** is a crucial buffer in the blood that helps maintain pH. Its excretion would reduce buffering capacity. - However, in cases of metabolic acidosis (like lactic acidosis), the body tries to **conserve** HCO3- or uses it to buffer excess H+ ions, rather than excrete it, until its stores are depleted.

Question 49: During exercise in physiological limits, what is the effect on end systolic volume?

A. ESV decreases (Correct Answer)
B. ESV increases
C. ESV first decreases and then increases
D. ESV remains unchanged

Explanation: ***ESV decreases*** - During exercise, **sympathetic nervous system activity** increases, leading to enhanced cardiac contractility. - Improved contractility allows the heart to eject a greater percentage of its end-diastolic volume, resulting in a smaller **residual volume** in the ventricle after systole. *ESV increase* - An increase in ESV would indicate a **reduced ejection fraction** and poorer cardiac efficiency, which is contrary to the physiological adaptations during exercise. - This typically occurs in conditions of **heart failure** or myocardial dysfunction, not healthy exercise. *ESV first decrease and then increases* - While there are complex physiological responses during exercise, the primary and sustained effect on ESV within physiological limits is a **net decrease** due to increased contractility. - A subsequent increase would suggest a decline in cardiac function or the onset of fatigue beyond physiological limits. *ESV remain unchanged* - An unchanged ESV would imply no significant alteration in **cardiac contractility** or **ejection efficiency**, which is inconsistent with the cardiovascular demands and adaptations during exercise. - The body actively works to optimize cardiac output by increasing stroke volume, partly by reducing ESV during exercise.

Question 50: During exercise increase in O2 delivery to muscles is because of all except:

A. Increased blood flow to muscles
B. Oxygen dissociation curve shifts to left (Correct Answer)
C. Increased extraction of oxygen from the blood
D. Increased stroke volume

Explanation: ***Oxygen dissociation curve shifts to left*** - During exercise, the **oxygen dissociation curve actually shifts to the right** (Bohr effect), facilitating the release of oxygen to deprived tissues. - A left shift would mean **hemoglobin binds more tightly to oxygen**, making it harder for oxygen to be delivered to exercising muscles. *Increased blood flow to muscles* - **Vasodilation** in the active muscles directs a larger proportion of the cardiac output to meet their metabolic demands. - This significantly increases the amount of **oxygenated blood** reaching the muscle tissue. *Increased extraction of oxygen from the blood* - Exercising muscles have a **higher metabolic rate** and thus a greater demand for oxygen. - This leads to a larger **arteriovenous oxygen difference**, meaning more oxygen is removed from the blood as it passes through the capillaries. *Increased stroke volume* - The heart pumps a **greater volume of blood per beat**, increasing cardiac output. - This contributes to the overall increase in **blood flow to the systemic circulation**, including the muscles.

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

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Fatigue Mechanisms

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Recovery Processes

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Training Principles and Adaptations

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Exercise Testing and Prescription

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