Exercise Physiology Exam 1 Study Guide

Thyroid Stimulating Hormone (TSH)

This hormone is released by the pituitary gland to stimulate the thyroid when thyroid hormone levels are low.

Anti-Diuretic Hormone (ADH)

After severe dehydration, this hormone is released by the pituitary to make kidneys conserve water and prevent further blood volume loss.

Cortisol

This hormone rises during stress to increase glucose levels and suppress the immune system.

Renin

This enzyme-hormone is released by the kidneys after blood pressure drops, triggering a pathway to raise blood pressure.

Estrogen

In females, this hormone rises during puberty and regulates menstrual cycles, breast development, and fat distribution.

Epinephrine

This hormone is released by the adrenal medulla during fight-or-flight situations, increasing heart rate and opening airways.

Aldosterone

This hormone helps retain sodium (and water) in the kidneys, increasing blood volume and pressure.

Estrogen (again)

This hormone surges mid-cycle in females to help prepare the uterus for a potential pregnancy.

Testosterone

In males, this hormone rises during puberty to cause facial hair growth, deeper voice, and increased muscle mass.

Insulin

Insulin is stimulated, released by the beta cells of the pancreas.

Ghrelin

Ghrelin is the hunger hormone released by the stomach when empty; it stimulates appetite.

Leptin

Leptin is the satiety hormone produced by fat cells; it signals the brain to reduce appetite and increase energy use.

Leptin resistance

Leptin resistance is when the brain ignores leptin's "stop eating" signal despite high leptin levels, leading to increased hunger and weight gain.

Glucagon

Glucagon, released by the alpha cells of the pancreas, stimulates the liver to release glucose by breaking down glycogen, maintaining blood sugar for muscles.

What are the body's three main ATP-producing systems?

1. Phosphagen System (ATP-PCr system)

2. Anaerobic Glycolysis

3. Aerobic System (Oxidative Phosphorylation)

How does exercise duration and intensity decide which energy system dominates?

High intensity, short duration (up to 10 sec): Phosphagen system

Moderate intensity, 30 sec to 2 min: Anaerobic glycolysis

Low intensity, long duration (minutes+): Aerobic system

Which adaptations improve aerobic ATP production?

1. Increased mitochondrial density

2. Improved capillary density

3. Increased cardiac output and lung capacity

Oxygen deficit

the short period at the start of exercise when the body's oxygen supply cannot meet the immediate demand of the working muscles, forcing the body to use anaerobic energy systems to produce ATP

Smaller oxygen deficit in trained athletes

They reach steady-state oxygen consumption faster, relying less on anaerobic metabolism, leading to less oxygen debt and quicker recovery.

Cellular and cardiovascular changes in trained athletes

- Increased mitochondrial density; - Enhanced capillary networks; - Improved stroke volume and cardiac output; - Faster activation of oxidative enzymes.

Which immediate energy stores supply ATP at the start?

ATP stored in muscles and phosphocreatine (PCr) supply immediate energy during the first ~10 seconds.

When does glycolysis dominate?

Glycolysis dominates during high-intensity exercise lasting from about 10 seconds to 2 minutes, producing ATP anaerobically.

How do lactate and hydrogen ions affect pH?

Accumulation of lactate and hydrogen ions lowers muscle pH, causing acidosis and muscle fatigue.

How is pH buffered? What restores pH after exercise?

Buffer systems like bicarbonate neutralize excess hydrogen ions. After exercise, pH is restored by removal of lactate through oxidation and conversion back to glucose (Cori cycle), and by breathing off CO₂.

What happens to catecholamines, heart rate (HR), and metabolism?

Catecholamines (epinephrine, norepinephrine) increase to stimulate heart rate, energy mobilization, and metabolism during the sprint. HR rises sharply to deliver oxygen and nutrients. Metabolism shifts to support rapid ATP production anaerobically and aerobically.

Why is O₂ consumption elevated after intense work?

To restore the body to its pre-exercise state by replenishing energy stores, removing metabolic byproducts, and repairing tissues.

Which factors drive the rapid vs. slow phase of recovery?

Rapid phase: Replenishment of phosphocreatine (PCr), oxygen restoration, normalization of heart rate and breathing.

Slow phase: Lactate removal, elevated body temperature, hormone balancing, and tissue repair.

How do PCr, lactate removal, heart rate (HR), and temperature contribute to recovery?

PCr is replenished quickly during the rapid phase, requiring oxygen.

Lactate removal happens mostly in the slow phase through oxidation or conversion to glucose.

Heart rate is elevated initially and returns to resting levels during recovery.

Elevated temperature increases metabolic rate, prolonging oxygen consumption in the slow phase

Lactate threshold (LT) in untrained individuals

~50-60% VO₂max

Lactate threshold (LT) in trained individuals

~70-85% VO₂max or higher

Adaptations that shift lactate threshold to a higher %VO₂max

Increased mitochondrial density and oxidative enzymes, Improved capillary density, Enhanced lactate clearance, Greater use of aerobic metabolism

How lactate is shuttled and reused as fuel

Lactate is transported to other tissues via lactate shuttles, where it's oxidized for energy or converted to glucose in the liver (Cori cycle).

Crossover concept

It describes how the body shifts from primarily burning fat at low intensity to carbohydrates at higher intensity exercise.

Fuels at low vs. high intensity exercise

Low intensity: Fat; High intensity: Carbohydrates.

Catecholamines and fuel use

Catecholamines increase carbohydrate use by stimulating glycogen breakdown.

Fast-twitch fibers and fuel use

Fast-twitch fibers prefer carbohydrates, increasing CHO use during intense exercise.

Low-carb diet and performance

It increases fat use but reduces glycogen stores, which may impair high-intensity performance and limit rapid energy availability.

RER

RER (Respiratory Exchange Ratio) is the ratio of carbon dioxide produced to oxygen consumed (VCO₂ / VO₂); it measures fuel use during exercise.

RER and exercise intensity

RER increases with exercise intensity, shifting from fat use (RER ~0.7) at low intensity to carbohydrate use (RER ~1.0) at high intensity.

RER 0.7

RER 0.7 → 100% fat

RER 0.85

RER 0.85 → Mix of fat and carbs

RER 1.0

RER 1.0 → 100% carbohydrate

Order of events in oxidative phosphorylation

NADH/FADH₂ donate electrons, ETC pumps H⁺ ions, Proton gradient forms, ATP synthase makes ATP, O₂ accepts electrons to form water.

How oxidative phosphorylation makes ATP aerobically

Electrons from NADH/FADH₂ move through the ETC, powering proton pumps that create a gradient. ATP synthase uses this gradient to make ATP. Oxygen is required as the final electron acceptor.

Hormones maintaining blood glucose during long-duration exercise

Glucagon, epinephrine, norepinephrine, cortisol, and growth hormone

Response of GH, cortisol, epinephrine, and norepinephrine to exercise intensity

All increase with intensity. Epinephrine and norepinephrine rise quickly; cortisol and GH increase more with prolonged or intense workouts.

Effect of prolonged exercise on insulin levels

Insulin levels decrease, helping to maintain blood glucose and allowing glucagon and other hormones to mobilize fuel.

Hormonal response to pre-workout meal vs. during workout

Pre-workout carbs increase insulin briefly, lowering fat metabolism. During exercise: insulin decreases, glucagon and stress hormones increase.

Best timing for pre-workout meal

Best to eat 1-2 hours before to avoid insulin spikes during training.

Plasma volume change with sweat loss

Plasma volume decreases, blood becomes more concentrated, and blood pressure drops.

ADH response to fluid loss

ADH increases water reabsorption in the kidneys.

Aldosterone response to fluid loss

Aldosterone promotes sodium (and water) reabsorption to conserve fluid and maintain blood volume.

Dehydration effects on heart rate during exercise

Dehydration lowers plasma volume and stroke volume. Heart rate increases to maintain cardiac output — a response known as cardiovascular drift.

T₃ and T₄

They increase basal metabolic rate by stimulating oxygen consumption, heat production, and metabolism of proteins, carbs, and fats.

Hypothyroidism

Hypothyroidism causes low metabolic rate, fatigue, reduced endurance, and slower muscle recovery.

Cortisol influence on gluconeogenesis, fat use, and immunity

It stimulates gluconeogenesis, promotes fat breakdown, and suppresses immune function during stress.

Cortisol helpful vs. harmful to performance

Helpful in short bursts to mobilize energy and aid recovery; harmful if chronically elevated, causing muscle loss and fatigue.

Cortisol highest during the day

Highest in the early morning; disruption of this rhythm affects sleep, mood, metabolism, and health.

GH and fat metabolism

GH stimulates fat breakdown for energy and promotes protein synthesis for muscle growth and tissue repair.

Exercise intensity and GH secretion

GH secretion increases with exercise intensity, especially at moderate to high intensities and longer durations.

Effect of elevated temperature on enzyme speed

Moderate heat speeds up enzyme activity, but excessive heat denatures enzymes and reduces performance.

Role of heat shock proteins

They protect and repair proteins damaged by heat, helping cells survive heat stress.

Dangerous fever temperature

Fever above ~40°C (104°F) can cause protein damage, organ failure, and heat stroke.

VO₂ max

The maximum rate of oxygen consumption during intense exercise, indicating aerobic fitness.

Physiological factors limiting VO₂ max

Cardiac output, oxygen delivery (hemoglobin), and muscle oxygen utilization.

Verification of true VO₂ max

By observing a plateau in oxygen consumption despite increased intensity, an RER >1.1, max heart rate, and exhaustion.

VO₂, HR, lactate, and pH in steady vs. graded exercise

In steady-state: VO₂ and HR plateau, lactate low, pH stable. In graded: VO₂ and HR rise continuously, lactate accumulates, pH drops.

Importance of steady-state for RER fuel measurement

Because oxygen supply matches demand, allowing accurate substrate use assessment via RER.

Time to regulate oxygen demand during exercise

About 2-3 minutes per stage during graded exercise tests.

Effect of low plasma volume on heart rate and performance

It lowers stroke volume, causing heart rate to increase and reducing exercise performance.

Hormones that conserve fluid during dehydration

ADH, aldosterone, and renin help conserve water and sodium.

Effect of dehydration on VO₂ max

Dehydration decreases VO₂ max by reducing blood volume and oxygen delivery.

Moderate training and URTI risk

It reduces URTI risk by boosting immune function.

Open window after long/intense exercise

A temporary period of immune suppression lasting 3-72 hours, increasing infection risk.

Regular exercise impact on vaccine response

It improves vaccine response by enhancing immune function and antibody production.

Intense exercise and muscle pH

By producing lactic acid which releases H⁺ ions, increasing acidity.

Buffers counteracting H⁺ during intense exercise

Bicarbonate, phosphates, proteins, and carnosine buffer H⁺ ions.

Role of mitochondria in acid load

They aerobically metabolize pyruvate, reducing lactate and H⁺ production.

Free radicals production during exercise

Mitochondria generate reactive oxygen species during increased oxygen use; immune cells and enzymes also contribute.

Adaptations limiting oxidative stress with training

Increased antioxidant enzymes, improved mitochondrial efficiency, and better repair systems.

Anabolism

Anabolism builds molecules (e.g., protein synthesis).

Catabolism

Catabolism breaks them down (e.g., glycolysis).

NAD/FAD

They carry electrons from metabolic reactions to the electron transport chain.

Electron acceptance

Oxygen accepts electrons in the electron transport chain, forming water.

Glycogen availability in middle-distance events

Low glycogen impairs power and endurance in anaerobic-heavy middle-distance events.

Perceived exertion with low carb

Less glucose leads to quicker fatigue and higher perceived effort.

Late-night training risks for Type 1 diabetics

Risk of nocturnal hypoglycemia due to delayed insulin effects and muscle glucose uptake overnight.

ACE inhibitors prescription and exercise BP effects

Prescribed for hypertension; they lower BP which can cause dizziness during exercise.

Body's hormonal response to dehydration in marathon running

Releases ADH and aldosterone to conserve water and sodium, reducing urine output.

Body temperature regulation during exercise vs. fever

Exercise: sweating and skin blood flow increase; Fever: hypothalamus raises set point, reduces sweating, causes shivering.

GLP-1's natural role and GLP-1 drugs

Naturally boosts insulin, reduces glucagon, slows gastric emptying; drugs mimic this for glucose control and appetite suppression.

How do resting HR and stroke volume differ between trained Twin A and sedentary Twin B?

Twin A: lower HR, higher SV; Twin B: higher HR, lower SV.

What are the mitochondrial differences between Twin A and Twin B?

Twin A has more and more efficient mitochondria; Twin B has fewer and less efficient ones.

How does blood volume differ between trained and sedentary twins?

Twin A has higher blood/plasma volume; Twin B has lower blood volume.

What difference in erythropoietin levels exists between the twins?

Twin A has higher EPO due to training, increasing RBCs; Twin B has baseline levels.

Describe differences in energy metabolism, RER, H+ accumulation, and lactate fate with training.

Twin A relies more on aerobic metabolism, has lower RER, better H+ buffering, and uses lactate as fuel; Twin B relies more on anaerobic metabolism, higher RER, and accumulates more H+ and lactate.

Renin-angiotensin system

Renin-Angiotensin-Aldosterone System (RAAS) regulates blood pressure, with steps including low blood pressure triggering the kidneys to release renin

RAAS Steps Diagram