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Introduction to Exercise Science for Fitness Professionals: Modifications to Breathing

Introduction to Exercise Science for Fitness Professionals
Modifications to Breathing
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table of contents
  1. Cover
  2. Title Page
  3. Copyright
  4. Table Of Contents
  5. Attribution and OER Revision Statement
  6. Chapter 1: Body Systems Review
    1. The Cardiovascular System
    2. The Nervous System
    3. Reflexes
    4. The Skeletal System
    5. Divisions of the Skeletal System
    6. Skeletal Muscle
    7. Divisions of the Skeletal Muscles
    8. Describing Motion and Movements
    9. Identify Anatomical Locations
  7. Chapter 2: Biomechanics and Human Movement
    1. The Basics of Biomechanics
    2. Inertia and Momentum
    3. Force
    4. Doing Work
    5. Body Levers
    6. Nervous System Control of Muscle Tension
    7. Muscle Tissue and Motion
  8. Chapter 3: Exercise Metabolism
    1. Introduction to Bioenergetics and Metabolism
    2. Overview of Metabolic Reactions
    3. Metabolic States of the Body
    4. The Cardiorespiratory System and Energy Production
    5. ATP in Living Systems
    6. Types of Muscle Fibers
    7. Exercise and Muscle Performance
    8. Nutrition, Performance, and Recovery
    9. Carbohydrate Metabolism
    10. Protein Metabolism
    11. Lipid Metabolism
  9. Chapter 4: Fitness Principles
    1. What are Physical Activity and Exercise?
    2. The Physical Activity Guidelines for Americans
    3. Components of Health-Related Fitness
    4. Principles of Adaptation and Stress
    5. FITT Principle
    6. Rest, Recovery, and Periodization
    7. Reversibility
    8. Training Volume
    9. Individual Differences
    10. Creating a Successful Fitness Plan
    11. Additional Safety Concerns
    12. Test Your Knowledge
  10. Chapter 5: Flexibility Training Principles
    1. What is Flexibility?
    2. Benefits of Flexibility and Stretching
    3. Improving Range of Motion
    4. Improving Flexibility
    5. Creating an Effective Stretching Program
    6. Assessing Your Flexibility
    7. Test Your Knowledge
  11. Chapter 6: Cardiorespiratory Training Principles
    1. What are the Cardiovascular and Respiratory Systems?
    2. Introduction: The Cardiovascular System
    3. Introduction: The Respiratory System
    4. The Process of Breathing and Respiratory Function
    5. Modifications to Breathing
    6. Changes in the CR System
    7. Measuring Heart Rate
    8. Measuring Intensity
    9. Cardiorespiratory Fitness Assessment
    10. Test Your Knowledge
  12. Chapter 7: Core and Balance Training Principles
    1. Lumbar Spine
    2. Abdomen
    3. The Pelvic Girdle
    4. Creating Movement at the Hip
    5. Balance
    6. Center of Gravity
    7. Supporting the Body
    8. Friction in Joints
    9. Human Stability
    10. Guidelines for Core and Balance Training
  13. Chapter 8: Plyometrics, Speed, Agility, and Quickness Training Principles
    1. Plyometric Exercises
    2. Variables of Plyometric Training
    3. Progressing a Plyometric Program
    4. Speed, Agility, and Quickness
    5. Speed
    6. Agility
    7. Quickness
  14. Chapter 9: Resistance Training Principles
    1. Resistance Exercise Programming
    2. Exercise Order
    3. Types of Resistance Training
    4. Basics of Form during Resistance Training
    5. Resistance Training Systems
    6. Resistance Training Conclusion
    7. Test Your Knowledge
  15. References
  16. Glossary
  17. MARC Record

51

Modifications to Breathing

Heather Ketchum and Eric Bright

Modifications to Breathing4

At rest, the respiratory system performs its functions at a constant, rhythmic pace, as regulated by the respiratory centers of the brain. At this pace, ventilation provides sufficient oxygen to all the tissues of the body. However, there are times that the respiratory system must alter the pace of its functions in order to accommodate the oxygen demands of the body.

Hyperpnea

Hyperpnea is an increased depth and rate of ventilation to meet an increase in oxygen demand as might be seen in exercise or disease, particularly diseases that target the respiratory or digestive tracts. This does not significantly alter blood oxygen or carbon dioxide levels, but merely increases the depth and rate of ventilation to meet the demand of the cells. In contrast, hyperventilation is an increased ventilation rate that is independent of the cellular oxygen needs and leads to abnormally low blood carbon dioxide levels and high (alkaline) blood pH.

Interestingly, exercise does not cause hyperpnea as one might think. Muscles that perform work during exercise do increase their demand for oxygen, stimulating an increase in ventilation. However, hyperpnea during exercise appears to occur before a drop in oxygen levels within the muscles can occur. Therefore, hyperpnea must be driven by other mechanisms, either instead of or in addition to a drop in oxygen levels. The exact mechanisms behind exercise hyperpnea are not well understood, and some hypotheses are somewhat controversial. However, in addition to low oxygen, high carbon dioxide, and low pH levels, there appears to be a complex interplay of factors related to the nervous system and the respiratory centers of the brain.

First, a conscious decision to partake in exercise, or another form of physical exertion, results in a psychological stimulus that may trigger the respiratory centers of the brain to increase ventilation. In addition, the respiratory centers of the brain may be stimulated through the activation of motor neurons that innervate muscle groups that are involved in the physical activity. Finally, physical exertion stimulates proprioceptors, which are receptors located within the muscles, joints, and tendons, which sense movement and stretching; proprioceptors thus create a stimulus that may also trigger the respiratory centers of the brain. These neural factors are consistent with the sudden increase in ventilation that is observed immediately as exercise begins. Because the respiratory centers are stimulated by psychological, motor neuron, and proprioceptor inputs throughout exercise, the fact that there is also a sudden decrease in ventilation immediately after the exercise ends when these neural stimuli cease, further supports the idea that they are involved in triggering the changes of ventilation.

High Altitude Effects

An increase in altitude results in a decrease in atmospheric pressure. Although the proportion of oxygen relative to gases in the atmosphere remains at 21 percent, its partial pressure decreases (Table). As a result, it is more difficult for a body to achieve the same level of oxygen saturation at high altitude than at low altitude, due to lower atmospheric pressure. In fact, hemoglobin saturation is lower at high altitudes compared to hemoglobin saturation at sea level. For example, hemoglobin saturation is about 67 percent at 19,000 feet above sea level, whereas it reaches about 98 percent at sea level.

Partial Pressure of Oxygen at Different Altitudes
Example locationAltitude (feet above sea level)Atmospheric pressure (mm Hg)Partial pressure of oxygen (mm Hg)
New York City, New York0760159
Boulder, Colorado5000632133
Aspen, Colorado8000565118
Pike’s Peak, Colorado14,00044794
Denali (Mt. McKinley), Alaska20,00035073
Mt. Everest, Tibet29,00026054

As you recall, partial pressure is extremely important in determining how much gas can cross the respiratory membrane and enter the blood of the pulmonary capillaries. A lower partial pressure of oxygen means that there is a smaller difference in partial pressures between the alveoli and the blood, so less oxygen crosses the respiratory membrane. As a result, fewer oxygen molecules are bound by hemoglobin. Despite this, the tissues of the body still receive a sufficient amount of oxygen during rest at high altitudes. This is due to two major mechanisms. First, the number of oxygen molecules that enter the tissue from the blood is nearly equal between sea level and high altitudes. At sea level, hemoglobin saturation is higher, but only a quarter of the oxygen molecules are actually released into the tissue. At high altitudes, a greater proportion of molecules of oxygen are released into the tissues. Secondly, at high altitudes, a greater amount of BPG is produced by erythrocytes, which enhances the dissociation of oxygen from hemoglobin. Physical exertion, such as skiing or hiking, can lead to altitude sickness due to the low amount of oxygen reserves in the blood at high altitudes. At sea level, there is a large amount of oxygen reserve in venous blood (even though venous blood is thought of as “deoxygenated”) from which the muscles can draw during physical exertion. Because the oxygen saturation is much lower at higher altitudes, this venous reserve is small, resulting in pathological symptoms of low blood oxygen levels. You may have heard that it is important to drink more water when traveling at higher altitudes than you are accustomed to. This is because your body will increase micturition (urination) at high altitudes to counteract the effects of lower oxygen levels. By removing fluids, blood plasma levels drop but not the total number of erythrocytes. In this way, the overall concentration of erythrocytes in the blood increases, which helps tissues obtain the oxygen they need.

Acute mountain sickness (AMS), or altitude sickness, is a condition that results from acute exposure to high altitudes due to a low partial pressure of oxygen at high altitudes. AMS typically can occur at 2400 meters (8000 feet) above sea level. AMS is a result of low blood oxygen levels, as the body has acute difficulty adjusting to the low partial pressure of oxygen. In serious cases, AMS can cause pulmonary or cerebral edema. Symptoms of AMS include nausea, vomiting, fatigue, lightheadedness, drowsiness, feeling disoriented, increased pulse, and nosebleeds. The only treatment for AMS is descending to a lower altitude; however, pharmacologic treatments and supplemental oxygen can improve symptoms. AMS can be prevented by slowly ascending to the desired altitude, allowing the body to acclimate, as well as maintaining proper hydration.

Acclimatization

Especially in situations where the ascent occurs too quickly, traveling to areas of high altitude can cause AMS. Acclimatization is the process of adjustment that the respiratory system makes due to chronic exposure to a high altitude. Over a period of time, the body adjusts to accommodate the lower partial pressure of oxygen. The low partial pressure of oxygen at high altitudes results in a lower oxygen saturation level of hemoglobin in the blood. In turn, the tissue levels of oxygen are also lower. As a result, the kidneys are stimulated to produce the hormone erythropoietin (EPO), which stimulates the production of erythrocytes, resulting in a greater number of circulating erythrocytes in an individual at a high altitude over a long period. With more red blood cells, there is more hemoglobin to help transport the available oxygen. Even though there is low saturation of each hemoglobin molecule, there will be more hemoglobin present, and therefore more oxygen in the blood. Over time, this allows the person to partake in physical exertion without developing AMS.

Chapter Review

Normally, the respiratory centers of the brain maintain a consistent, rhythmic breathing cycle. However, in certain cases, the respiratory system must adjust to situational changes in order to supply the body with sufficient oxygen. For example, exercise results in increased ventilation, and chronic exposure to a high altitude results in a greater number of circulating erythrocytes. Hyperpnea, an increase in the rate and depth of ventilation, appears to be a function of three neural mechanisms that include a psychological stimulus, motor neuron activation of skeletal muscles, and the activation of proprioceptors in the muscles, joints, and tendons. As a result, hyperpnea related to exercise is initiated when exercise begins, as opposed to when tissue oxygen demand actually increases.

In contrast, acute exposure to a high altitude, particularly during times of physical exertion, does result in low blood and tissue levels of oxygen. This change is caused by a low partial pressure of oxygen in the air, because the atmospheric pressure at high altitudes is lower than the atmospheric pressure at sea level. This can lead to a condition called acute mountain sickness (AMS) with symptoms that include headaches, disorientation, fatigue, nausea, and lightheadedness. Over a long period of time, a person’s body will adjust to the high altitude, a process called acclimatization. During acclimatization, the low tissue levels of oxygen will cause the kidneys to produce greater amounts of the hormone erythropoietin, which stimulates the production of erythrocytes. Increased levels of circulating erythrocytes provide an increased amount of hemoglobin that helps supply an individual with more oxygen, preventing the symptoms of AMS.

Glossary

acclimatization
process of adjustment that the respiratory system makes due to chronic exposure to high altitudes
acute mountain sickness (AMS)
condition that occurs a result of acute exposure to high altitude due to a low partial pressure of oxygen
hyperpnea
increased rate and depth of ventilation due to an increase in oxygen demand that does not significantly alter blood oxygen or carbon dioxide levels
hyperventilation
increased ventilation rate that leads to abnormally low blood carbon dioxide levels and high (alkaline) blood pH

Heather Ketchum & Eric Bright, OU Human Physiology Textbook. OpenStax CNX. Jun 18, 2015. Download for free at http://cnx.org/contents/e4f804ec-103f-4157-92e1-71eed7aa8584@1

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Copyright © 2021

                                by Amanda Shelton

            Introduction to Exercise Science for Fitness Professionals by Amanda Shelton is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.
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