EXPH 386 Final Case Study Questions

A clinician is using Indirect Calorimetry to assess a patient's energy expenditure during an exercise test. This measurement technique works by

Measuring oxygen consumption and using that rate to estimate heat transfer

A weightlifter is performing an all-out, maximal effort lift that lasts 9 seconds. Which of the following statements most accurately describes the limits and function of the primary energy system fueling this effort?

The instantaneous breakdown of ATP releases approximately 4 seconds worth of energy, which is immediately replenished by stored CP.

During prolonged, low-intensity exercise, a trained individual increases their rate of lipolysis. Which group of hormones released during this activity is responsible for activating Hormone Sensitive Lipase (HSL), the enzyme responsible for breaking down stored fat?

Epinephrine, Norepinephrine, Glucagon, and Growth Hormone

The total net ATP produced from the complete aerobic oxidation of one glucose molecule is 30 ATP in skeletal muscle fibers, whereas it is 32 ATP in heart and liver tissue. This yield discrepancy is caused by:

The specific hydrogen shuttle system (Glycerol Phosphate vs. Malate Aspartate) used to transport NADH across the mitochondrial membranes.

The transfer of energy from an exergonic reaction to drive an endergonic process is fundamental to cellular survival. The exergonic breakdown of stored fuel ultimately drives which vital endergonic process?

The re-synthesis of Adenosine Triphosphate (ATP) from ADP and phosphate.

An athlete’s strenuous 400-meter sprint requires a high rate of glycolysis, resulting in significant lactate accumulation. This lactate production in a healthy cell is primarily driven by:

The rapid speed of glycolysis causing the production rate of protons (NADH) to exceed the mitochondria’s capacity to process them.

The final stage of fat metabolism involves the long fatty acid chain being repetitively cleaved into two-carbon fragments via Beta Oxidation. These two-carbon fragments are then converted directly into which molecule for entry into the Krebs Cycle?

Acetyl-CoA

A physician recommends a low-carbohydrate diet to a patient seeking weight loss through intense exercise. This strategy significantly increases the patient's risk of using protein for fuel because

The depletion of muscle glycogen forces the use of amino acids, which is measurable by an increase in sweat urea nitrogen.

Which macronutrient is the only one whose stored energy can generate ATP through anaerobic processes?

Carbohydrates

The concept that "fats burn in a carbohydrate flame" means that the degradation of fatty acids in the Krebs Cycle relies on a continued, albeit minimal, supply of carbohydrate-derived metabolites to supply:

Oxaloacetate, which must combine with Acetyl-CoA to form Citrate.

According to the Second Law of Thermodynamics, potential energy tends to degrade into kinetic energy with a lower capacity to do work, ultimately resulting in a conversion to

Heat

When comparing the net ATP yield from glycolysis starting with blood glucose versus starting with stored muscle glycogen, the net yield from glycogen is 3 ATP, while the net yield from glucose is 2 ATP. This difference is due to the process of glycogenolysis bypassing which specific metabolic step?

The initial ATP-requiring phosphorylation step (Step 1).

Aerobic endurance training leads to enhanced fat utilization during submaximal exercise. A key structural adaptation that supports this enhanced fat burning is the training-induced increase in:

The density of mitochondria and capillaries in the muscle.

14. The primary factor that biochemists believe dictates the rate of breakdown of carbohydrates, fats, and amino acids (the metabolic mill) is the cellular concentration of:

ADP (or the ATP to ADP ratio).

What is the fundamental function of molecular oxygen (O2​) in the process of cellular respiration?

It serves as the final electron acceptor in the Electron Transport Chain (ETC).]

The high-energy electrons collected by NADH during glycolysis must be transported from the cytosol into the mitochondria. In skeletal muscle, this transport system results in FADH2​ being formed within the mitochondria, which enters the ETC at a lower potential energy. This shuttle is known as the:

Glycerol Phosphate Shuttle

Before the carbon skeleton of a protein can be utilized for energy, the nitrogen must be removed. When this nitrogen removal occurs in the skeletal muscle tissue, the process is called:

Transamination

Enzymes are sensitive to environmental conditions. During intense exercise, the buildup of metabolic acids (like lactic acid) lowers the cellular pH, which can cause the rate-limiting enzyme of glycolysis to become less effective. This enzyme is:

Phosphofructokinase (PFK)

Which statement accurately explains why lipids (fats) provide significantly more heat of combustion (energy dense) per gram compared to carbohydrates or proteins?

Lipids possess more hydrogen atoms that can be oxidized compared to the other macronutrients.

A person consumes a low glycemic index carbohydrate 45 minutes before starting a workout. The metabolic rationale for choosing a low glycemic index food prior to exercise is to:

Avoid a rapid insulin surge that could lead to subsequent hypoglycemia during the workout.

A sprinter runs the 100-meter dash in 10 seconds. What is the predominant immediate energy source supporting this maximal effort activity?

Stored high-energy phosphates (ATP and phosphocreatine)

The rate of energy transfer from high-energy phosphates (ATP/PCr) is approximately how much faster than the rate of energy transfer from aerobic metabolism?

Four to eight times higher

An individual who has never participated in regular aerobic exercise is undergoing a graded exercise test. At what percentage of their Max V˙O2​ would their Onset of Blood Lactate Accumulation (OBLA) typically be observed?

50% to 55%

A high-level marathon runner is tested. Their OBLA threshold is measured at 85% of Max V˙O2​. This shift in the OBLA threshold to a higher intensity is a characteristic adaptation of which type of training?

aerobic/Endurance training

Which physiological adaptation in anaerobically trained athletes (like sprinters) causes them to have the highest net lactate production capabilities compared to untrained or aerobically trained individuals?

Upregulation of glycolytic enzymes and increased intramuscular glycogen stores

After a maximal effort test lasting three minutes, an athlete needs to quickly clear the accumulated blood lactate. What recovery method is considered most efficient for lactate clearance?

Alternating light to moderate intensity aerobic exercise

During a submaximal treadmill test, an individual's oxygen consumption plateaus and remains constant for the duration of the stage, meeting the ATP demands of the current constant workload. This phenomenon is referred to as what?

Steady State (Steady Rate)

A healthy, sedentary individual performs a maximal graded exercise test (GXT). They stop due to discomfort and muscle fatigue before their oxygen consumption shows a definitive plateau, achieving the highest value they could sustain. This result should be classified as a(n)

VO˙2​ Peak

A research team needs to compare the cardiorespiratory fitness levels of 10 students who have widely varying body weights. Which unit of VO˙2​ should the team use to accurately compare their fitness levels relative to population norms?

Milliliters per kilogram of body weight per minute

A client performs 60 minutes of vigorous intensity interval training. Which factor is the key driver determining the magnitude and duration (potentially up to 24 hours) of the slow component of excess post-oxygen consumption (EPOC)?

Intensity of the exercise

A patient is taking a beta blocker medication to manage blood pressure. The clinical exercise physiologist determines that prescribing exercise intensity based on heart rate may be inaccurate due to medication effects. Instead, they should utilize

Rating of Perceived Exertion (RPE)

16. During a maximal graded exercise test, the RER value is measured at 1.15. This value, which is significantly above 1.0, is primarily influenced by which non-metabolic factor?

Buffering of accumulated lactic acid by sodium bicarbonate, releasing extra CO2​

A metabolic cart measures an individual's resting Respiratory Quotient (RQ) value as 0.75 after a 12-hour fast. This indicates that the individual is predominantly metabolizing which fuel source?

Fats

For the average healthy individual, what component accounts for the largest percentage (60% to 75%) of their Total Daily Energy Expenditure (TDEE)?

Basal Metabolic Rate (BMR)

Open circuit spirometry systems typically report VO˙2​ volumes in VSTPD units. This standardization is necessary because gas volume is influenced by temperature and pressure differences in the environment. Normalizing gas measurements to standard temperature, standard pressure, and dry removes the effects of:

Altitude, water vapor, and heat (Standard Temperature, Pressure, and Dry)

If a volume of gas is subjected to increased pressure while temperature remains constant, the volume will decrease. This inverse relationship between pressure and volume is described by which gas law?

Boyle's Law

An athlete sustains an ACL tear and is casted for six weeks with the ankle held in a position of sustained plantar flexion (a shortened position). Holding the calf muscles (like the soleus and gastrocnemius) in a shortened position during immobilization primarily leads to what structural adaptation within the muscle fibers?

Loss of sarcomeres arranged in series

Following the six-week casting period, the athlete's leg muscles are observed to be stiff. A common effect observed in the immobilized muscle, contributing to this stiffness, is an increase in which specific connective tissue layer?

Perimysium.

The athlete begins rehabilitation, and following months of intense resistance training, achieves significant muscle hypertrophy. According to the Myonuclear Domain Hypothesis, why must the muscle fiber acquire new myonuclei from satellite cells to achieve this sustained increase in size?

Each myonucleus controls a fixed amount of cytoplasm, so adding nuclei is necessary to control the increased volume.

During recovery from intense eccentric training, the muscle relies on satellite cells for repair and growth. Where are the quiescent (resting) satellite cells located relative to the muscle fiber boundary?

Adjacent to the T-tubules, where they can sense action potentials.

The athlete's quadriceps femoris (a pennate muscle) is integral to producing the high force needed for sprinting acceleration. The pennate arrangement favors high force production primarily because it allows for an increase in the number of sarcomeres arranged in what configuration?

Sarcomeres attached only to the M-line.

When the nerve impulse (action potential) reaches the axon terminal, causing the release of Acetylcholine (ACh) into the synaptic space, the channels that open to facilitate this neurotransmitter release allow the entry of which specific type of calcium?

Extracellular calcium, entering the nerve terminal.

After the muscle fiber depolarizes, the action potential travels down the Transverse (T) tubules. Which specialized protein, embedded in the T-tubule membrane, acts as the voltage sensor that detects the action potential and signals the release of calcium?

Dihydropyridine Receptor (DHPR).

During the process of Excitation-Contraction (EC) Coupling, the immediate source of calcium that directly triggers the interaction of contractile proteins is the:

Sarcoplasmic Reticulum (SR).

Following the end of the action potential, the muscle fiber needs to relax. Which specialized protein actively pumps calcium back into the Sarcoplasmic Reticulum (SR), initiating muscle relaxation?

SERCA protein.

Once intracellular calcium is released into the sarcoplasm, it triggers contraction by binding to which component of the regulatory complex?

Troponin C.

According to the Sliding Filament Theory, how does the sarcomere shorten during a concentric contraction?

The thick and thin filaments slide past each other without changing their individual lengths.

To ensure continuous, smooth tension rather than jerky, oscillatory movements during a sustained contraction, the myosin heads within a sarcomere perform the power stroke in which manner?

Asynchronously, so that constant crossbridge formation is maintained.

If the athlete performs an isometric contraction with the muscle held at a length significantly shorter than optimal (highly compressed), the force output is reduced. This reduction is primarily due to which mechanical limitation?

Physical interference and obstacles as opposing actin filaments collide.

During the myosin power stroke cycle, the release of which specific molecule from the myosin head signals the pivotal movement that pulls the actin filament inward?

ADP.

To achieve maximal jumping power during a plyometric drill, the CNS must rapidly recruit all available motor units. Which motor unit type is associated with the highest force output, fastest contraction speed, and lowest resistance to fatigue?

Fast Fatiguable (FF)

The athlete performs an eccentric lift using a weight that is 150% of his maximum capability (1RM), causing rapid muscle lengthening. This demonstrates that during eccentric actions, heavier loads lead to what characteristic of movement?

Faster lengthening velocities and force production above isometric maximum

An elite marathon runner, known for prolonged aerobic endurance, would have muscles that primarily express Type I fibers. These fibers are characterized by:

Low Myosin ATPase activity and high resistance to fatigue.

Comparing the performance curves of muscles with high Type II fiber density (e.g., a weightlifter) versus high Type I fiber density (e.g., a marathon runner), the Type II muscle exhibits:

Higher maximal force output and higher velocity potential (Vmax​)

During a depth jump, the athlete lands, and the muscle is forcefully stretched while activated. Which sensory receptor is located deep within the muscle belly, senses this forceful stretch, and responds by signaling the central nervous system to make the muscle contract even harder (the stretch reflex)?

Muscle Spindle

If the athlete attempts to lift an extremely heavy load, generating dangerously high tension at the muscle's attachment point, which sensory receptor detects this excessive tension and elicits a reflex inhibition, telling the muscle to relax to prevent damage?

Golgi Tendon Organ (GTO)

A patient's cardiac echo indicates a phase where the ventricular pressure is rapidly increasing, but the volume remains constant because both the mitral and aortic valves are closed. This physiological phase is best characterized as:

Isovolumetric contraction.

During auscultation, a physician hears the second heart sound (S2/Dub). Physiologically, the S2 sound signals the closure of which valves and the start of which cardiac phase?

Semilunar valves; start of diastole.

An otherwise healthy 80-year-old patient develops a complete block leading to an intrinsic heart rate of approximately 45 beats per minute. Based on the concept that the heart's electrical system has backup pacemakers with slower intrinsic rates, which cardiac structure is most likely functioning as the current pacemaker?

Atrioventricular (AV) node.

A continuous ECG strip shows a regular rhythm but consistently lacks P-waves. The resulting lack of atrial depolarization would most immediately compromise which component of the cardiac cycle, leading to reduced volume?

Active ventricular filling (atrial topping off).

An athlete begins maximal exercise, causing Cardiac Output (CO) to rise from 5 L/min to 20 L/min. Given that Total Peripheral Resistance (TPR) simultaneously falls from 19 units to 6.5 units, the resulting increase in Mean Arterial Pressure (MAP) is expected because:

Increased cardiac output, even with decreased resistance, creates greater pressure on the aortic walls due to increased volume output.

Which physiological response during aerobic exercise primarily leads to a reduction in Afterload on the left ventricle?

Vasodilation in active skeletal muscle beds, reducing Total Peripheral Resistance.

A highly trained track athlete's heart rate rapidly climbs from 50 bpm to 105 bpm as she approaches the starting blocks, before any physical activity begins. This initial anticipatory increase in heart rate is primarily achieved by:

Rapid removal or withdrawal of parasympathetic (vagal) tone.

A clinician records a patient's seated resting blood pressure reading as 124/92 mmHg. According to the established clinical categories, how should this blood pressure be classified?

Stage 2 Hypertension.

During sustained exercise, faster blood flow through the vessels causes increased shear stress on the innermost lining of the arteries. This triggers the release of Nitric Oxide (NO), which then causes:

The heart to increase contractility via Beta-1 receptor activation.

During intense aerobic activity, the sympathetic nervous system causes systemic vasoconstriction throughout the body. However, the active quadriceps muscles experience massive vasodilation and increased blood flow. This essential localized override of central sympathetic signals is known as:

Chronotropic regulation.

Chronic endurance training leads to physiological remodeling of the heart (eccentric hypertrophy). This differs from the pathological remodeling (concentric hypertrophy) seen in chronic hypertension because only physiological hypertrophy involves:

An increase in the muscle's purely aerobic oxidative capacity.

Following several weeks of stopping chronic endurance training, V̇O₂ max rapidly declines. The most significant decrease in V̇O₂ max in the first few weeks is driven primarily by the loss of:

Peripheral adaptations (capillary density and mitochondrial enzymes).

A runner maintains a constant pace (steady-state intensity) during a 60-minute session in a warm room. After 30 minutes, her heart rate begins to climb steadily while her stroke volume begins to fall. This cardiovascular drift occurs because:

Core temperature rises, requiring increased blood flow to the skin for heat dissipation, which reduces venous return and preload.

During a maximal exercise test, Stroke Volume (SV) plateaus around 50% of V̇O₂ max while Heart Rate (HR) continues to increase linearly. The physiological limit causing this SV plateau is:

High heart rate severely restricts the time available for ventricular filling (diastolic time).

A sedentary patient completes a 6-month exercise program. Based on the Fick equation (VO2​=CO×A-VO2​ difference), which combination of training adaptations would be necessary to increase VO2​ max?

Reduced afterload and maximal venous oxygen content.

Veins function as low-pressure capacity vessels and rely on one-way valves. The primary mechanism responsible for driving the deoxygenated blood from the lower extremities back up to the heart against gravity is the

High elasticity of the vein walls accommodating large blood volume.

Although the QRS complex signals ventricular depolarization, the actual mechanical contraction starts slightly after the electrical event. This small time delay is required for:

Calcium ions to enter the contractile cells, bind to troponin, and initiate actin-myosin cross-bridge formation.

High pulsatile pressure leaving the left ventricle must be reduced to a smooth, continuous flow before entering the exchange vessels. The vessels primarily responsible for this function, acting as high-resistance channels and causing the greatest drop in blood pressure, are the

Arterioles and small arteries.

A patient with a history of heart disease is undergoing an exercise test and reports chest pain (angina pectoris) when their RPP reaches 18,000. For subsequent exercise prescription, the clinician should use this RPP value to:

Limit the patient’s maximal target workload to an RPP significantly below 18,000 to prevent future episodes of myocardial ischemia.

A pulmonary specialist notes that while the patient's lung tissue appears fragile microscopically, the organ maintains significant structural integrity despite trauma. This strength, described as being similar to a honeycomb or a beehive, is primarily attributed to

The shared walls and interwoven collagen and elastin fibers within the alveoli.

A patient enters respiratory distress. Physicians note that the primary physiological goal of increasing the patient's minute ventilation (V˙E​) is not solely to increase O2​ saturation (which is already 98%), but rather to normalize the blood's chemical balance. This necessity highlights that the automatic, day-to-day control of breathing is primarily driven by the need to regulate:

Carbon dioxide levels (CO2​) and subsequent pH balance.

An anesthesiologist prepares a patient for surgery. She knows that air delivered to the alveoli (the source) has a partial pressure of oxygen (PA​O2​) of approximately 100 mmHg. However, the oxygen partial pressure in the systemic arteries (Pa​O2​) is measured as slightly lower, about 97 mmHg. The initial drop in O2​ partial pressure from the atmosphere (∼159 mmHg) to the alveoli (∼100 mmHg) is due to:

Water vapor pressure (humidification) and the offloading of CO2​ into the alveoli.

A patient has a traumatic injury that renders the diaphragm unresponsive. According to Boyle's Law, what is the direct mechanical consequence of this muscle failing to contract and move downward?

Chest volume decreases, causing intrapulmonary pressure to rise above atmospheric pressure, stopping inspiration.

A young athlete diagnosed with asthma experiences acute bronchospasm during a track meet. The patient's primary difficulty lies in moving air due to increased airway resistance. This resistance is generally highest in which segment of the respiratory system in a healthy lung, and where does smooth muscle contraction primarily affect the asthmatic patient?

Highest in the upper and middle-sized bronchi; contraction affects the middle-sized airways lacking cartilage.

A 65-year-old former smoker undergoes spirometry testing. The results show an FEV1​/FVC ratio of 45% (normal is ∼80%) and a significantly prolonged exhalation time. Based on this characteristic pattern, the physician would categorize this disease as:

Obstructive, caused by air trapping due to increased resistance upon exhalation.

An elderly patient shows a decrease in Vital Capacity (VC) compared to when they were younger, but an increase in Residual Volume (RV). This change in lung volumes that occurs naturally with age is primarily attributed to:

A loss of elasticity in the lung tissue itself (elastin fibers).

A researcher observes that a patient is breathing 6 L/min (V˙E​) with a tidal volume (VT​) of 500 mL and a respiratory rate of 12 breaths/min. If the patient has an anatomical dead space of 150 mL, what is the patient's Alveolar Ventilation (V˙A​)?

B. 4.2 L/min

A patient develops pulmonary fibrosis, a condition where the barrier between the alveoli and the capillaries thickens. Based on Fick's Law of Diffusion, what is the predicted effect on gas exchange efficiency, particularly during exercise?

Gas exchange efficiency decreases because the thickness of the membrane (T) increases.

During rapid gas exchange, the body must effectively move both O2​ into the blood and CO2​ out of the blood across the thin alveolar-capillary membrane. The pulmonary system rarely experiences trouble eliminating CO2​ even in the early stages of lung disease because

CO2​ is roughly 20 times more diffusible/soluble than O2​.

A victim of carbon monoxide (CO) poisoning arrives at the hospital. CO has a high affinity for hemoglobin, rendering the molecule unable to carry O2​. Given that a normal person consumes ∼250 mL O2​/min at rest, why is CO poisoning acutely life-threatening?

The dissolved O2​ fraction is extremely small and insufficient to meet resting metabolic demand.

An elite marathon runner is tested at maximal exercise. Compared to rest, the arterial oxygen content (O2​ delivered to tissues) remains stable, but the venous oxygen content (returning to the heart) is significantly lower. This physiological change reflects:

An increase in the amount of oxygen extracted and consumed by the working tissues (A-V difference).

During intense training, an athlete's muscles generate heat and metabolic byproducts, including CO2​ and H+ ions (decreasing pH). These changes collectively cause the oxygen dissociation curve (ODC) to shift to the right. This "Bohr Effect" facilitates:

Greater offloading of O2​ from hemoglobin to the metabolically active tissues.

A significant portion (approximately 60%) of CO2​ is transported from the tissues to the lungs. This essential function relies mainly on the CO2​ being converted into which compound inside the red blood cell, with the help of carbonic anhydrase?

Bicarbonate (HCO3−​).

A patient begins to hyperventilate rapidly due to acute anxiety, while their metabolic production of CO2​ remains constant. Applying the Alveolar Ventilation Equation, what short-term change would be expected in the patient's arterial CO2​ levels (Pa​CO2​)?

Pa​CO2​ will decrease, leading to respiratory alkalosis.

A patient is hypoventilating due to an opioid overdose that depresses the respiratory centers in the brainstem. This decrease in breathing rate leads to an accumulation of CO2​ in the blood. Based on the relationship between CO2​ and pH, this accumulation will cause:

An increase in H+ ions and respiratory acidosis.

The central chemoreceptors located near the medulla are primarily responsible for regulating the autonomic breathing rate in a resting, healthy individual. These receptors are highly sensitive to

Changes in CO2​ and cerebral spinal fluid (CSF) pH.

A patient is confirmed to be hypoxic (Pa​O2​<80 mmHg). Arterial blood gas analysis reveals a normal Alveolar-Arterial PO2​​ Gradient (A-a PO2​​ difference). Which of the following is the only likely cause of the patient's hypoxemia?

Hypoventilation.

An intrapulmonary shunt is defined as blood flowing past an alveolar unit that receives no ventilation (zero V). From a V/Q perspective, what does a unit experiencing a partial obstruction of its airway (low V, normal Q) mimic?

A Shunt (low V/Q ratio).

During a maximal exercise test, a subject's Ventilatory Equivalent (V˙E​/V˙O2​​) line breaks upward sharply (Ventilatory Threshold, VT). This non-linear increase in breathing efficiency is directly attributable to

The production of CO2​ resulting from the buffering of lactic acid produced by anaerobic metabolism.