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Introduction to Exercise Science for Fitness Professionals: Changes in the CR System

Introduction to Exercise Science for Fitness Professionals
Changes in the CR System
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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

52

Changes in the CR System

Dawn Markell and Diane Peterson

An improvement in CR functioning, or fitness level, requires adaptation of the system. Remember, the point is to more effectively generate ATP so more work can be accomplished. In order to process more oxygen and deliver more oxygenated blood to the cells, the overall system must undergo changes to make this possible. Here is a list of adaptations that occur to the CR system as a result of consistent aerobic exercise:

  • Resting heart rate may decrease. The average resting heart rate hovers around 70–75 beats per minute. Elite athletes may have resting heart rates in the high 30s. Generally, resting heart rate may decrease by approximately 10 beats per minute with chronic exercise.
  • Pulmonary adaptations, such as increased tidal volume (the amount of oxygen entering the lungs with each breath) and increased diffusion capacity (the amount of oxygen that enters the blood stream from the lungs). This allows for more oxygen to enter the pulmonary circulation en route to the left side of the heart.
  • The heart muscles, specifically the left side of the heart, increase in size making it possible to contract more forcefully. As a result, more blood can be pumped with each beat meaning more oxygen can be routed to the systemic circulation.
  • More oxygen is delivered and transported into the cells where ATP production can occur. This is called the arterial-vein difference (a-VO2diff)

These changes in the system are not permanent due to the principle of reversibility. Following a period of inactivity, the benefits from chronic aerobic exercise will be reversed.

Assessing CR Fitness

To adequately prepare for starting a personal fitness program, it is important to first assess your current level of fitness. There are multiple methods for assessing a person’s level of fitness. Each of the walking/jogging assessments discussed here attempts to estimate a key physiological marker of the heart’s and lungs’ functioning capacity and maximal oxygen consumption. Maximal oxygen consumption, or VO2 max, measures the body’s maximum ability to take in and utilize oxygen, which directly correlates to overall health and fitness. A good estimate of VO2 max provides a one-time glance at a person’s health and fitness level and a baseline measurement for reassessment at future dates to gauge improvements.

Some of the most common walking/jogging assessments used to estimate VO2 max include the 12-Minute Walk, 1.5-Mile Run/Walk Test, 3-Minute Step Test, and 1-Mile Walk Test. Unfortunately, these field assessments, although practical and inexpensive, only provide estimations. More accurate assessments require a lab-based VO2 max test using equipment that measures the volume of oxygen and carbon dioxide being moved in and out of the air passages during exercise. Although this test is more accurate, the expense and availability make it impractical for most. Unlike the lab test, the field assessments are relatively cost free, user-friendly and require very little expertise to conduct or perform. In addition, the key point of the assessment is measuring differences rather than absolute values, and the field tests accurately meet that objective.

Information on how to safely perform these assessments will be provided at the end of this chapter.


Dawn Markell & Diane Peterson, Health and Fitness for Life. MHCC Library Press. Sept 4, 2019. https://mhcc.pressbooks.pub/hpe295

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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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