Exercise Physiology Practice Questions

Q: Which of the following changes is noted during exercise?

Body temperature increases.. **Explanation:** **Correct Option: B (Body temperature increases)** During exercise, muscle contraction involves the conversion of chemical energy (ATP) into mechanical work. However, this process is only about 20-25% efficient; the remaining 75-80% of energy is released as **metabolic heat**. This leads to a rise in core body temperature, which triggers thermoregulatory mechanisms like cutaneous vasodilation and sweating. **Analysis of Incorrect Options:** * **Option A:** While cardiac output increases significantly, **cerebral blood flow remains constant** (approximately 750 ml/min) due to powerful autoregulation. While systolic blood pressure rises, the brain is protected from these fluctuations to maintain a stable environment. * **Option C:** Lymphatic flow from active muscles **increases** significantly (up to 10-30 fold). This is due to increased capillary hydrostatic pressure (leading to more interstitial fluid) and the "muscle pump" effect, which propels lymph toward the thoracic duct. * **Option D:** Blood flow to muscles increases **immediately** at the onset of exercise (within 1-2 seconds). This is initiated by "command signals" from the CNS and maintained by local metabolic factors (adenosine, $K^+$, $H^+$, and $CO_2$) causing rapid vasodilation. **High-Yield NEET-PG Pearls:** * **The "Active Hyperemia" Effect:** Local metabolites are the primary drivers of increased muscle blood flow during exercise, overriding sympathetic vasoconstriction (Functional Sympatholysis). * **Oxygen Dissociation Curve:** During exercise, the curve shifts to the **Right** (due to increased $H^+$, $CO_2$, Temperature, and 2,3-BPG), facilitating oxygen unloading to tissues. * **Blood Pressure:** Systolic BP increases, but **Diastolic BP** usually remains stable or decreases slightly due to a massive drop in Total Peripheral Resistance (TPR).

Q: Which of the following is NOT a mechanism that increases blood supply to muscles during exercise?

Inhibition of beta receptors. **Explanation:** During exercise, the body must redistribute cardiac output to active skeletal muscles. This is achieved through a combination of local and systemic mechanisms. **Why "Inhibition of beta receptors" is the correct answer:** Skeletal muscle blood vessels contain **Beta-2 ($\beta_2$) receptors**. When stimulated by circulating epinephrine, these receptors cause **vasodilation**, which increases blood flow. Therefore, **inhibition** (blockade) of beta receptors would cause vasoconstriction or prevent dilation, thereby **decreasing** blood supply to the muscles. This is why the option is the "odd one out." **Analysis of Incorrect Options:** * **Local metabolites (Active Hyperemia):** This is the most potent mechanism for exercise-induced vasodilation. Accumulation of lactate, $CO_2$, $H^+$, Adenosine, and $K^+$ ions causes direct relaxation of precapillary sphincters. * **Sympathetic stimulation:** While sympathetic alpha-1 stimulation causes general vasoconstriction, the overall effect during exercise is a massive increase in cardiac output and "sympatholysis" (where local metabolites override sympathetic constriction in active muscles), ensuring increased flow. * **Cholinergic stimulation:** Skeletal muscles receive **Sympathetic Cholinergic** fibers. These release acetylcholine, which acts on muscarinic receptors to cause vasodilation, specifically during the "anticipatory phase" just before exercise begins. **High-Yield Pearls for NEET-PG:** * **Most important factor** for increased blood flow during exercise: **Local metabolites** (Active Hyperemia). * **Sympathetic Cholinergic System:** Unique to skeletal muscle; responsible for the initial increase in blood flow before metabolic products accumulate. * **Vascular Resistance:** During exercise, Total Peripheral Resistance (TPR) **decreases** due to massive vasodilation in skeletal muscle beds, despite vasoconstriction in the viscera.

Q: In a 40-year-old person, what is the estimated maximum heart rate?

180 bpm. **Explanation:** The maximum heart rate (MHR) is the highest number of beats per minute a person's heart can safely reach during maximum physical exertion. In clinical physiology and sports medicine, the most widely accepted and high-yield formula for estimating MHR is the **Fox-Haskell formula**: **Maximum Heart Rate (MHR) = 220 – Age (in years)** For a 40-year-old individual: $MHR = 220 - 40 = 180 \text{ bpm}$ **Analysis of Options:** * **Option B (180 bpm):** Correct. This aligns perfectly with the standard physiological calculation ($220 - 40$). * **Option A (160 bpm):** Incorrect. This would be the MHR for a 60-year-old ($220 - 60$). * **Option C (200 bpm):** Incorrect. This would be the MHR for a 20-year-old ($220 - 20$). * **Option D (220 bpm):** Incorrect. This represents the constant used in the formula, or the theoretical MHR of a newborn. **High-Yield Facts for NEET-PG:** 1. **Age-Dependency:** MHR decreases linearly with age due to a decrease in the intrinsic heart rate and a reduction in the sensitivity of beta-adrenergic receptors in the SA node. 2. **Target Heart Rate (THR):** For moderate-intensity exercise, the target is usually 50–70% of the MHR. For vigorous intensity, it is 70–85%. 3. **Tanaka Formula:** A more precise (though less commonly tested) formula is $208 - (0.7 \times \text{Age})$. 4. **Clinical Correlation:** MHR is a critical parameter during **Treadmill Testing (TMT)**. A test is often considered "diagnostic" if the patient reaches 85% of their age-predicted MHR.

Q: Which of the following is NOT a physiological change during severe exercise?

Decreased paO2. In exercise physiology, maintaining arterial blood gas homeostasis is a key regulatory mechanism. Here is the breakdown of the physiological changes: **Why "Decreased paO2" is the Correct Answer:** In a healthy individual, even during severe exercise, **arterial oxygen tension (paO2) does not decrease.** The respiratory system is highly efficient; the increase in alveolar ventilation matches or even exceeds the increase in oxygen consumption ($VO_2$). While the *venous* $O_2$ content drops significantly as tissues extract more oxygen, the *arterial* $PO_2$ remains normal (~100 mmHg) or may slightly increase due to hyperventilation. **Analysis of Incorrect Options:** * **Hyperventilation (A):** At the onset of exercise, there is an immediate "neurogenic" increase in ventilation (driven by the cerebral cortex and joint proprioceptors) followed by humoral adjustments. * **Hyperkalemia (B):** During strenuous exercise, repeated muscle depolarization leads to an efflux of Potassium ($K^+$) from the skeletal muscle cells into the extracellular fluid. This transient hyperkalemia is a classic finding in severe exercise. * **Decreased paCO2 (D):** During severe (anaerobic) exercise, lactic acid accumulates. The resulting metabolic acidosis stimulates peripheral chemoreceptors, leading to compensatory hyperventilation. This "blows off" $CO_2$, causing the arterial $PCO_2$ to drop below normal resting levels. **High-Yield Clinical Pearls for NEET-PG:** * **Diffusion Capacity:** $O_2$ diffusion capacity increases up to 3-fold during exercise due to increased pulmonary capillary perfusion and recruitment. * **Oxy-hemoglobin Curve:** Exercise shifts the curve to the **Right** (due to increased $H^+$, $CO_2$, Temperature, and 2,3-DPG), facilitating $O_2$ unloading at tissues. * **Anaerobic Threshold:** The point where lactic acid starts accumulating and $V_E$ (ventilation) increases disproportionately to $VO_2$.

Q: Soreness and pain in muscles after vigorous exercise is due to -

Lactic acidosis. **Explanation:** **Why Lactic Acidosis is the Correct Answer:** During vigorous or strenuous exercise, the oxygen demand of the skeletal muscles exceeds the supply provided by the cardiovascular system. To meet the energy requirements, muscles switch from aerobic metabolism to **anaerobic glycolysis**. In this pathway, pyruvate is converted into **lactic acid** by the enzyme lactate dehydrogenase (LDH). The accumulation of lactic acid leads to a drop in local pH (lactic acidosis), which irritates sensory nerve endings (nociceptors), resulting in the characteristic sensation of muscle soreness and burning pain during or immediately after exercise. **Analysis of Incorrect Options:** * **A. Hyperkalemia:** While potassium shifts from the intracellular to the extracellular space during muscle contraction, it primarily contributes to muscle fatigue rather than acute soreness. * **C. Hyperthermia:** Vigorous exercise increases core body temperature due to metabolic heat production, but this causes systemic exhaustion or heat cramps rather than localized muscle soreness. * **D. Hyponatremia:** Low sodium levels (often due to excessive water intake during endurance sports) lead to confusion, seizures, or generalized muscle cramps, but not the specific soreness associated with anaerobic exertion. **High-Yield Facts for NEET-PG:** * **Cori Cycle:** Lactic acid produced in the muscles is transported to the liver, where it is converted back into glucose (gluconeogenesis). * **Oxygen Debt:** The extra oxygen required after exercise to metabolize accumulated lactate and restore ATP/creatine phosphate stores is known as the "Oxygen Debt" or EPOC (Excess Post-exercise Oxygen Consumption). * **DOMS (Delayed Onset Muscle Soreness):** While acute pain is due to lactic acid, soreness occurring 24–48 hours later is primarily due to microscopic tears in muscle fibers (microtrauma) and subsequent inflammation, not lactic acid.

Q: Which of the following does not increase during isotonic exercise?

Total peripheral resistance. **Explanation:** In **isotonic (dynamic) exercise**, such as running or swimming, the body undergoes significant cardiovascular adjustments to meet the increased oxygen demand of skeletal muscles. **Why Total Peripheral Resistance (TPR) decreases:** The hallmark of isotonic exercise is **marked vasodilation** in the active skeletal muscle beds, mediated by local metabolic factors (e.g., increased $K^+$, $H^+$, adenosine, and $CO_2$). Although there is sympathetic vasoconstriction in non-essential organs (like the kidneys and GI tract), the massive vasodilation in the large muscle mass significantly outweighs this, leading to a **net decrease in Total Peripheral Resistance.** **Why the other options are incorrect:** * **Heart Rate (C):** Increases significantly due to sympathetic stimulation and withdrawal of parasympathetic (vagal) tone to increase cardiac output. * **Stroke Volume (D):** Increases due to increased venous return (skeletal muscle pump) and increased myocardial contractility (Frank-Starling mechanism and sympathetic effect). * **Respiration Rate (A):** Increases (hyperpnea) to enhance gas exchange and meet the metabolic demands of the tissues, driven by central command and peripheral chemoreceptors. **High-Yield Clinical Pearls for NEET-PG:** * **Isotonic vs. Isometric:** In **Isotonic** exercise, TPR decreases and Pulse Pressure increases. In **Isometric (static)** exercise (e.g., weightlifting), TPR may actually increase or stay the same due to mechanical compression of blood vessels, leading to a sharper rise in Mean Arterial Pressure. * **Systolic BP** increases in isotonic exercise, while **Diastolic BP** usually remains constant or decreases slightly (due to decreased TPR). * **Cardiac Output ($CO = HR \times SV$):** Both components increase, leading to a 4–6 fold increase in CO in elite athletes.

Question 1

Which of the following changes is noted during exercise?

Accepted Answer

Body temperature increases.

Answer

Blood flow to the brain increases with an increase in mean systolic blood pressure.

Answer

Lymphatic flow from muscles decreases.

Answer

Blood flow to muscles increases after half a minute.

Question 2

In a 100-meter dash, most of the energy consumed by skeletal muscles to replenish ATP is derived from which source?

Accepted Answer

Phosphocreatine

Answer

Aerobic glycolysis

Answer

Oxidation of fatty acids

Answer

None of the above

Question 3

Which of the following is NOT a mechanism that increases blood supply to muscles during exercise?

Accepted Answer

Inhibition of beta receptors

Answer

Local metabolites

Answer

Sympathetic stimulation

Answer

Cholinergic stimulation

Question 4

In a 40-year-old person, what is the estimated maximum heart rate?

Accepted Answer

180 bpm

Answer

160 bpm

Answer

200 bpm

Answer

220 bpm

Question 5

All of the following are TRUE about isometric exercises, EXCEPT:

Accepted Answer

Useful in ventricular arrhythmia

Answer

S3, S4 is accentuated

Answer

Increases systemic vascular resistance

Answer

Diastolic murmur of Mitral stenosis becomes louder

Question 6

Which of the following is NOT a physiological change during severe exercise?

Accepted Answer

Decreased paO2

Answer

Hyperventilation in the beginning

Answer

Hyperkalemia

Answer

Decreased paCO2

Question 7

Which of the following is not increased during isometric exercise?

Accepted Answer

Total peripheral resistance

Answer

Respiratory rate

Answer

Heart rate

Answer

Stroke volume

Question 8

Soreness and pain in muscles after vigorous exercise is due to -

Accepted Answer

Lactic acidosis

Answer

Hyperkalemia

Answer

Hyperthermia

Answer

Hyponatremia

Question 9

Which of the following does not increase during isotonic exercise?

Accepted Answer

Total peripheral resistance

Answer

Respiration rate

Answer

Heart rate

Answer

Stroke volume

Question 10

Which of the following is NOT a true change in the circulating blood flow of an exercising muscle?

Accepted Answer

Peripheral resistance increases.

Answer

Complete flow stops on maximal tension reaching 70% of maximum.

Answer

Blood supply increases by approximately 30 times between contractions.

Answer

Dilation of arterioles and pre-capillary sphincters occurs.

Exercise Physiology — MCQs

Exercise Physiology — MCQs

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