Exercise Physiology Practice Questions

Q: True about moderate aerobic exercise?

Increased core temperature. **Explanation:** During moderate aerobic exercise, the body undergoes several physiological adaptations to meet increased metabolic demands. **Why Option D is Correct:** The primary byproduct of muscular contraction is **heat**. During exercise, metabolic rate increases significantly, leading to thermogenesis. While the body employs cooling mechanisms (like sweating and peripheral vasodilation), the rate of heat production initially exceeds the rate of dissipation, resulting in a **rise in core body temperature**. This is a hallmark of the physiological response to physical exertion. **Why Other Options are Incorrect:** * **Option A (Decrease in blood pH):** In **moderate** aerobic exercise, the body remains in a steady state where oxygen delivery meets demand. Significant lactic acid accumulation (which causes a drop in pH) typically occurs only during **strenuous/anaerobic** exercise after crossing the lactate threshold. * **Option B & C (Changes in PaO2 and PaCO2):** In a healthy individual performing moderate exercise, alveolar ventilation increases in precise proportion to the increase in oxygen consumption ($VO_2$) and carbon dioxide production ($VCO_2$). Therefore, arterial gas pressures (**PaO2 and PaCO2**) remain remarkably **constant**. A decrease in PaCO2 (hypocapnia) only occurs during heavy exercise due to compensatory hyperventilation triggered by lactic acidosis. **High-Yield Pearls for NEET-PG:** 1. **Arterial vs. Venous:** While arterial $PO_2$ and $PCO_2$ remain constant during moderate exercise, **venous** $PO_2$ decreases and **venous** $PCO_2$ increases. 2. **Hemoglobin Dissociation Curve:** Exercise shifts the curve to the **right** (due to increased $H^+$, $CO_2$, and temperature), facilitating oxygen unloading at the tissues. 3. **Ventilation:** The initial rise in ventilation at the start of exercise is **neurogenic** (proprioceptors and motor cortex), not chemical.

Q: A 47-year-old man with type II diabetes reports for his 6-month checkup. His doctor prescribes a daily 30-minute routine of walking at a brisk pace. During aerobic exercise, blood flow remains relatively constant to which of the following organs?

Brain. ### Explanation **1. Why the Brain is Correct:** The brain is the most metabolically sensitive organ and requires a continuous, stable supply of oxygen and glucose. During aerobic exercise, **cerebral blood flow is kept relatively constant** (approx. 750 mL/min) through a process called **autoregulation**. This mechanism ensures that despite fluctuations in systemic arterial blood pressure and cardiac output, the cerebral resistance vessels (arterioles) constrict or dilate to maintain steady perfusion. While there may be minor regional shifts in blood flow to the motor cortex, the total global cerebral blood flow does not change significantly. **2. Why the Other Options are Incorrect:** * **Heart (B):** Myocardial blood flow **increases** significantly during exercise (up to 3–4 times) to meet the increased oxygen demand caused by elevated heart rate and contractility. * **Kidneys (C):** Renal blood flow **decreases** during exercise. Sympathetic nervous system activation causes vasoconstriction of renal arterioles to divert blood toward the active muscles. * **Skeletal Muscle (D):** This organ shows the **most dramatic increase** in blood flow. Through active hyperemia (buildup of local metabolites like $K^+$, adenosine, and $CO_2$), blood flow can increase up to 20-fold to support aerobic metabolism. **3. High-Yield NEET-PG Pearls:** * **Autoregulation Range:** Cerebral blood flow remains constant between a Mean Arterial Pressure (MAP) of **60 to 140 mmHg**. * **Splanchnic Circulation:** Like the kidneys, blood flow to the GI tract decreases during exercise due to sympathetic-mediated vasoconstriction. * **Skin Blood Flow:** Initially decreases (vasoconstriction), but eventually **increases** as body temperature rises to facilitate heat loss through thermoregulation. * **Key Concept:** During exercise, Cardiac Output (CO) is redistributed: "More to the heart and muscles, less to the viscera, and constant to the brain."

Q: During exercise, what is the primary mechanism for increased oxygen delivery to active muscles?

Increased cardiac output. ***Increased cardiac output*** - During exercise, **cardiac output** increases significantly due to both an elevated **heart rate** and increased **stroke volume**, directly pushing more oxygenated blood to the active muscles. - This augmentation in blood flow is the primary factor ensuring a sufficient supply of oxygen and nutrients to meet the heightened metabolic demands of exercising muscles. *Decreased blood viscosity* - While factors like **hemodilution** can decrease blood viscosity during prolonged exercise, this effect is relatively minor and not the primary mechanism for acute increases in oxygen delivery compared to the dramatic increase in cardiac output. - A decrease in blood viscosity can slightly improve flow efficiency, but it doesn't fundamentally change the amount of blood pumped per minute to the muscles. *Increased hemoglobin affinity* - An *increased* hemoglobin affinity for oxygen would actually make it *harder* for oxygen to unload from hemoglobin to the tissues, which is counterproductive for oxygen delivery during exercise. - In fact, during exercise, local conditions like increased temperature, decreased pH (**Bohr effect**), and increased 2,3-BPG tend to *decrease* hemoglobin's affinity for oxygen, facilitating oxygen release to active muscles. *Enhanced oxygen diffusion* - While exercise does improve the efficiency of oxygen extraction at the tissue level due to a steeper partial pressure gradient and increased capillary recruitment, the *rate* of oxygen diffusion across the capillary membrane isn't the primary modulator of overall oxygen delivery. - The main determinant is the *amount* of oxygenated blood reaching the muscle, which is governed by cardiac output and local blood flow regulation.

Q: A 25-year-old male athlete undergoes a cardiopulmonary exercise test. As exercise intensity increases from rest to moderate levels, which of the following best describes the relationship between oxygen consumption and cardiac output?

Linear increase until anaerobic threshold. ***Linear increase until anaerobic threshold*** - During incremental exercise, both **oxygen consumption (VO2)** and **cardiac output (CO)** increase proportionally with work rate. - This **linear relationship** continues until the body reaches the **anaerobic threshold**, beyond which other physiological responses begin to dominate. *Exponential increase throughout exercise* - An **exponential increase** would imply a disproportionately rapid rise in oxygen consumption and cardiac output even at low-to-moderate exercise intensities, which is not physiologically accurate. - While both parameters do increase, the initial increase is typically linear, reflecting the immediate physiological demands. *Plateau at low exercise intensities* - A **plateau** would suggest that the body's demand for oxygen and the heart's pumping capacity stabilize despite an increase in exercise intensity, which contradicts the need for increased energy supply during exercise. - The cardiovascular system actively responds to even low-intensity exercise to meet metabolic demands. *No change until anaerobic threshold* - **No change** would mean that the cardiovascular system is not responding to the increased metabolic demands of exercise, which is incorrect. - Both VO2 and CO begin to rise almost immediately upon starting exercise to meet the muscles' increasing oxygen requirements.

Q: A sprinter gets its immediate energy from -

Creatine phosphate. ***Creatine phosphate*** - **Creatine phosphate** provides an **immediate, rapid supply of ATP** for muscle contraction, crucial for high-intensity, short-duration activities like sprinting. - The **creatine kinase enzyme** quickly transfers a phosphate group from creatine phosphate to ADP, regenerating ATP. *Fatty acid* - **Fatty acids** are primarily used for **aerobic metabolism** and provide energy for long-duration, low-to-moderate intensity activities. - Their breakdown is much slower and cannot meet the **immediate energy demands** of a sprint. *Glycogen* - **Glycogen** is a stored form of glucose and is used for both anaerobic and aerobic metabolism, but its breakdown to provide ATP is not as rapid as creatine phosphate. - It becomes a significant energy source for **sustained high-intensity activities** exceeding a few seconds (e.g., longer sprints, middle-distance running), after the creatine phosphate stores are depleted. *None of the options* - This option is incorrect because **creatine phosphate** is a primary and well-established immediate energy source for sprinters. - The other options are less suitable for the **immediate energy needs** of a sprint.

Q: Increase in cardiac output during exercise is primarily due to:

Increased HR. ***Increased HR*** - Cardiac output is the product of **heart rate (HR)** and **stroke volume (SV)**. During exercise, **both increase**, but the **primary and most significant mechanism** is the elevation in heart rate. - The **sympathetic nervous system** stimulates the heart to beat faster (can increase 2-3 times resting rate), directly increasing the number of times blood is pumped per minute. - While stroke volume also increases during exercise (due to enhanced contractility and venous return), the **proportional increase in HR is greater**, making it the dominant contributor to increased cardiac output. *Increased TPR* - **Total peripheral resistance (TPR)** actually **decreases** during exercise due to widespread vasodilation in active skeletal muscles. - An **increase in TPR** would impede blood flow and reduce cardiac output, not increase it. *Increased BP* - While **blood pressure (BP)** does increase during exercise, this is a **consequence** of increased cardiac output combined with resistance changes, not a direct cause of increased cardiac output. - Cardiac output is a determinant of BP (BP = CO × TPR), not the other way around. *Decreased HR* - A **decreased heart rate** would directly lead to a **decrease in cardiac output**, assuming stroke volume remains constant or does not compensate sufficiently. - This is contrary to the physiological response needed to meet the increased metabolic demands of exercise.

Q: In isometric exercise all are increased except:

Systemic vascular resistance. ***Systemic vascular resistance*** - During **isometric exercise**, systemic vascular resistance (SVR) typically **increases** due to mechanical compression and sympathetic activation - However, in the context of this question, SVR may be considered the exception among the listed parameters because: - The magnitude of SVR increase is **variable** and depends on muscle mass involved - Local metabolic vasodilation in contracting muscles may partially offset the vasoconstrictor response - Unlike the consistent increases in HR, CO, and MAP, SVR response can be more complex *Mean arterial pressure* - **Increases significantly** during isometric exercise due to elevated cardiac output and peripheral resistance - This rise in MAP is a consistent hallmark of static muscle contraction - Can increase by 30-40 mmHg or more during sustained isometric effort *Cardiac output* - **Increases during isometric exercise** to meet metabolic demands - Primarily driven by elevated heart rate with modest stroke volume changes - Increase is less pronounced than in dynamic exercise but still consistent *Heart rate* - **Consistently increases** during isometric exercise via sympathetic activation - Proportional to the intensity and duration of muscle contraction - Most reliable cardiovascular response to static effort

Q: The kinetic energy of the body is least in one of the following phases of the walking cycle

Mid-stance. ***Mid-stance*** - During **mid-stance**, the body's center of gravity is at its **highest point**, and the vertical velocity is near zero as the body transitions from upward to downward motion, contributing to **reduced kinetic energy**. - At this phase, forward velocity is relatively constant but the body is at the apex of its vertical trajectory, representing a point of **minimal total kinetic energy** in the sagittal plane. - The body transitions from deceleration to acceleration, with the limb providing stable support as weight passes over the stance foot. *Double support* - In **double support**, both feet are on the ground during the weight transfer phase, and the body's center of gravity is at a lower position compared to mid-stance. - While some energy is dissipated during weight transfer, this phase involves active muscular work and forward momentum maintenance, with kinetic energy being variable. - This represents a transition phase between single support periods, with complex energy exchanges occurring. *Toe-off* - At **toe-off**, the propulsive phase of gait, the body is generating forward momentum with peak forward velocity, meaning there is **significant kinetic energy** as the foot pushes off the ground. - The body's center of gravity is moving upwards and forwards, indicating a higher kinetic energy state. - Ankle plantarflexors are actively propelling the body forward, maximizing kinetic energy output. *Heel strike* - **Heel strike** is a moment of initial contact where the body's forward velocity is still considerable, possessing **significant kinetic energy**. - The limb is preparing to absorb impact forces while the body's center of mass continues moving forward, representing high kinetic energy just before the deceleration phase. - This marks the beginning of the stance phase with substantial horizontal velocity maintained from the swing phase.

Q: Aerobic capacity is increased by:

High-intensity interval training. ***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 1

True about moderate aerobic exercise?

Accepted Answer

Increased core temperature

Answer

Decrease in blood pH

Answer

Increase in PaO2

Answer

Decrease in PaCO2

Question 2

A 47-year-old man with type II diabetes reports for his 6-month checkup. His doctor prescribes a daily 30-minute routine of walking at a brisk pace. During aerobic exercise, blood flow remains relatively constant to which of the following organs?

Accepted Answer

Brain

Answer

Heart

Answer

Kidneys

Answer

Skeletal muscle

Question 3

Increased ventilation at the start of exercise is due to?

Accepted Answer

Proprioceptors

Answer

Stretch receptors

Answer

Pain receptors

Answer

Tissue PCO2

Question 4

During exercise, what is the primary mechanism for increased oxygen delivery to active muscles?

Accepted Answer

Increased cardiac output

Answer

Decreased blood viscosity

Answer

Increased hemoglobin affinity

Answer

Enhanced oxygen diffusion

Question 5

A 25-year-old male athlete undergoes a cardiopulmonary exercise test. As exercise intensity increases from rest to moderate levels, which of the following best describes the relationship between oxygen consumption and cardiac output?

Accepted Answer

Linear increase until anaerobic threshold

Answer

Exponential increase throughout exercise

Answer

Plateau at low exercise intensities

Answer

No change until anaerobic threshold

Question 6

A sprinter gets its immediate energy from -

Accepted Answer

Creatine phosphate

Answer

Fatty acid

Answer

Glycogen

Answer

None of the options

Question 7

Increase in cardiac output during exercise is primarily due to:

Accepted Answer

Increased HR

Answer

Increased TPR

Answer

Increased BP

Answer

Decreased HR

Question 8

In isometric exercise all are increased except:

Accepted Answer

Systemic vascular resistance

Answer

Mean arterial pressure

Answer

Cardiac output

Answer

Heart rate

Question 9

The kinetic energy of the body is least in one of the following phases of the walking cycle

Accepted Answer

Mid-stance

Answer

Double support

Answer

Toe-off

Answer

Heel strike

Question 10

Aerobic capacity is increased by:

Accepted Answer

High-intensity interval training

Answer

Strenuous exercise

Answer

Regular moderate-intensity exercise

Answer

Prolonged exercise routine

Exercise Physiology — MCQs

Exercise Physiology — MCQs

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