Exercise Physiology Practice Questions

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

Phosphocreatine. ***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.

Q: During exercise, blood flow to brain is

Remains unchanged. ***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.

Q: All of the following are features of exercise EXCEPT:

Left shift of Hb-O₂ dissociation curve. ***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.

Q: In severe exercise, decrease in pH is due to:

Lactic acidosis. ***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.

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

ESV decreases. ***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.

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

Oxygen dissociation curve shifts to left. ***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.

Q: Immediate soreness and fatigue in muscles during vigorous exercise is primarily due to?

Lactic acidosis. ***Lactic acidosis*** - During **vigorous exercise**, oxygen supply to muscles may be insufficient, leading to anaerobic metabolism and the accumulation of **lactic acid**. - This buildup of **lactic acid** lowers pH within muscle cells, which interferes with muscle contraction and causes immediate soreness and fatigue. *Hyponatremia* - **Hyponatremia** is a condition of low sodium concentration in the blood, often associated with prolonged, excessive fluid intake without adequate electrolyte replacement. - While it can cause muscle cramps and weakness, it typically manifests in **endurance events** (e.g., marathons) rather than immediate symptoms during vigorous exercise. *Hyperthermia* - **Hyperthermia** is an elevated body temperature due to overwhelmed thermoregulatory mechanisms, often seen in hot environments or prolonged intense activity. - It can lead to fatigue, weakness, and dizziness, but widespread immediate muscle soreness is more directly linked to **metabolic byproducts** rather than solely heat. *Hyperkalemia* - **Hyperkalemia** refers to elevated potassium levels in the blood, which can affect cardiac and neuromuscular function. - While it can lead to muscle weakness or paralysis, it is not a primary or immediate cause of post-exercise muscle soreness or fatigue in healthy individuals during typical vigorous exercise.

Q: Least useful for a 800-m run in a competitive event would be

Lohmann reaction. ***Lohmann reaction*** - The **Lohmann reaction** (creatine kinase reaction) is primarily involved in rapid, **short-burst energy production** for activities lasting a few seconds (e.g., sprints). - An 800-meter run is a middle-distance event requiring sustained energy from both anaerobic and aerobic pathways, where the immediate **phosphocreatine** system (Lohmann reaction) is quickly depleted and less useful for the majority of the race. *Pale muscle fibres* - **Pale muscle fibers** (Type II or fast-twitch fibers) are characterized by a high capacity for **anaerobic metabolism** and rapid, powerful contractions. - While they are crucial for the initial burst and speed in an 800-m run, their high glycolytic capacity makes them essential for the sustained high-intensity effort required, even as the race progresses beyond pure sprint. *Muscle glycogen* - **Muscle glycogen** is the primary stored carbohydrate fuel for **anaerobic glycolysis**, which is a significant energy pathway during the high-intensity portions of an 800-m run. - Its breakdown provides quick ATP generation without oxygen, supporting the rapid pace required throughout much of the race. *Oxidative phosphorylation* - **Oxidative phosphorylation** (aerobic respiration) becomes increasingly important as an 800-m race progresses, contributing a substantial portion of the ATP required for sustained muscle contraction. - It allows for the efficient production of large amounts of ATP when oxygen is available, crucial for maintaining pace and minimizing fatigue over the middle distance.

Q: For a person who is running, the main source of energy used in the first minute is:

Glycogen. ***Glycogen*** - For intense activities like running, especially in the first minute, the body primarily relies on **anaerobic metabolism** and readily available glucose stored as glycogen in muscles and the liver. - **Glycogenolysis** rapidly breaks down glycogen into glucose, which then enters glycolysis to produce ATP quickly, albeit inefficiently without oxygen. *Fat* - **Fat (triglycerides)** is a primary energy source for prolonged, lower-intensity exercise, as its breakdown via **beta-oxidation** and subsequent **oxidative phosphorylation** is slower and requires oxygen. - While fat provides more ATP per gram, its utilization is not as immediate as glycogen for high-intensity, short-duration efforts. *Glucose* - **Glucose** in the bloodstream is an immediate fuel source, but its supply is limited and quickly supplemented by **glycogenolysis** during intense exercise. - While glucose is the molecule ultimately catabolized for energy, it's primarily derived from glycogen stores rather than circulating glucose for the initial burst of high-intensity activity. *Phosphagen* - The **phosphagen system (creatine phosphate)** provides energy for extremely short, maximal bursts of effort (e.g., first 10-15 seconds of a sprint) by rapidly regenerating ATP. - While crucial for the very initial phase, its stores are depleted quickly and cannot sustain energy production for an entire minute of running.

Question 1

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

Accepted Answer

Phosphocreatine

Answer

Phosphofructokinase

Answer

Glucose 1 - phosphate

Answer

Creatine phosphokinase

Question 2

During exercise, blood flow to brain is

Accepted Answer

Remains unchanged

Answer

Increased

Answer

Decreased

Answer

Redirected to muscles

Question 3

All of the following are features of exercise EXCEPT:

Accepted Answer

Left shift of Hb-O₂ dissociation curve

Answer

Increased blood supply to muscles

Answer

Increased O₂ extraction

Answer

Increased stroke volume

Question 4

Aerobic capacity is increased by:

Accepted Answer

Prolonged exercise routine

Answer

Strenuous exercise

Answer

Spurt of exercise

Answer

Regular 3-minute exercise

Question 5

In severe exercise, decrease in pH is due to:

Accepted Answer

Lactic acidosis

Answer

Respiratory acidosis

Answer

H+ retention

Answer

HCO3 excretion

Question 6

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

Accepted Answer

ESV decreases

Answer

ESV increases

Answer

ESV first decreases and then increases

Answer

ESV remains unchanged

Question 7

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

Accepted Answer

Oxygen dissociation curve shifts to left

Answer

Increased blood flow to muscles

Answer

Increased extraction of oxygen from the blood

Answer

Increased stroke volume

Question 8

Immediate soreness and fatigue in muscles during vigorous exercise is primarily due to?

Accepted Answer

Lactic acidosis

Answer

Hyponatremia

Answer

Hyperthermia

Answer

Hyperkalemia

Question 9

Least useful for a 800-m run in a competitive event would be

Accepted Answer

Lohmann reaction

Answer

Pale muscle fibres

Answer

Muscle glycogen

Answer

Oxidative phosphorylation

Question 10

For a person who is running, the main source of energy used in the first minute is:

Accepted Answer

Glycogen

Answer

Fat

Answer

Glucose

Answer

Phosphagen

Exercise Physiology — MCQs

Exercise Physiology — MCQs

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