🏋️Exercise Testing and Prescription Unit 2 – Exercise Physiology

Key Concepts and Terminology

• Exercise physiology studies the body's responses and adaptations to physical activity and exercise
• Homeostasis maintains stable internal conditions in the body despite changes in the external environment
• VO2 max represents the maximum amount of oxygen an individual can utilize during intense exercise
• Cardiac output ($Q$) is the product of heart rate ($HR$) and stroke volume ($SV$), expressed as $Q = HR \times SV$
• Anaerobic threshold is the point during exercise at which lactic acid starts to accumulate in the blood
• FITT principle guides exercise prescription based on Frequency, Intensity, Time, and Type
• Specificity principle states that physiological adaptations are specific to the type of training performed
• Progressive overload involves gradually increasing the stress placed on the body during exercise to continually adapt and improve

Physiological Systems in Exercise

• Cardiovascular system delivers oxygen and nutrients to working muscles and removes metabolic waste products
  • Includes the heart, blood vessels, and blood
  • Adaptations to exercise include increased stroke volume, improved capillarization, and enhanced oxygen extraction
• Respiratory system facilitates gas exchange between the atmosphere and the blood
  • Consists of the lungs, airways, and respiratory muscles (diaphragm, intercostals)
  • Exercise-induced adaptations include increased lung volumes, improved ventilation-perfusion matching, and strengthened respiratory muscles
• Musculoskeletal system generates force and movement during exercise
  • Comprises skeletal muscles, bones, tendons, and ligaments
  • Adaptations to exercise include muscle hypertrophy, increased bone density, and improved joint stability
• Endocrine system regulates physiological processes through the secretion of hormones
  • Key hormones in exercise include cortisol, growth hormone, and insulin
  • Exercise can modulate hormone secretion and sensitivity, influencing metabolism and adaptation
• Thermoregulatory system maintains core body temperature within a narrow range
  • Involves heat production (metabolism) and heat dissipation (sweating, vasodilation)
  • Exercise challenges thermoregulation due to increased metabolic heat production

Energy Systems and Metabolism

• ATP (adenosine triphosphate) is the primary energy currency for cellular processes, including muscle contraction
• Phosphagen system provides rapid ATP production for short-duration, high-intensity activities (< 10 seconds)
  • Utilizes stored ATP and phosphocreatine (PCr) in the muscle
  • Anaerobic process that does not require oxygen
• Glycolytic system generates ATP through the breakdown of glucose or glycogen (1-3 minutes)
  • Anaerobic glycolysis occurs in the cytoplasm of muscle cells
  • Produces lactic acid as a byproduct, leading to muscle fatigue
• Oxidative system is the primary energy source for prolonged, lower-intensity activities (> 3 minutes)
  • Aerobic metabolism occurs in the mitochondria of muscle cells
  • Utilizes carbohydrates, fats, and proteins to produce ATP in the presence of oxygen
• Metabolic flexibility refers to the ability to switch between fuel sources (carbohydrates and fats) depending on exercise intensity and duration
• Excess post-exercise oxygen consumption (EPOC) represents the increased metabolic rate following exercise
  • Contributes to the overall energy expenditure of an exercise session
  • Magnitude and duration of EPOC depend on exercise intensity and duration

Cardiovascular and Respiratory Responses

• Heart rate increases linearly with exercise intensity to meet the increased oxygen demand of working muscles
• Stroke volume, the amount of blood ejected from the left ventricle per beat, increases during exercise due to enhanced contractility and venous return
• Cardiac output, the product of heart rate and stroke volume, can increase up to 5-6 times resting values during maximal exercise
• Blood flow is redistributed during exercise, with increased flow to active muscles and decreased flow to non-essential organs (gastrointestinal tract, kidneys)
• Ventilation, the volume of air inhaled and exhaled per minute, increases during exercise to meet the increased oxygen demand and remove carbon dioxide
• Tidal volume, the amount of air inhaled or exhaled per breath, increases during exercise, contributing to the overall increase in ventilation
• Respiratory rate, the number of breaths per minute, also increases during exercise to support the increased ventilation
• Oxygen uptake (VO2) represents the amount of oxygen consumed by the body per minute and is a key indicator of cardiovascular fitness
• Respiratory exchange ratio (RER) is the ratio of carbon dioxide production to oxygen consumption and reflects the relative contribution of carbohydrates and fats to energy production

Muscular Adaptations to Exercise

• Muscle fiber types: Type I (slow-twitch) fibers are fatigue-resistant and suited for endurance activities, while Type II (fast-twitch) fibers generate high force but fatigue quickly
• Muscle hypertrophy is the increase in muscle size due to an increase in the cross-sectional area of individual muscle fibers
  • Occurs in response to resistance training and is mediated by protein synthesis
  • Satellite cells, stem cells located near muscle fibers, contribute to hypertrophy by fusing with existing fibers
• Muscle strength is the maximum force a muscle or muscle group can generate against resistance
  • Increases due to neural adaptations (improved motor unit recruitment and firing rate) and muscle hypertrophy
• Muscle endurance is the ability of a muscle or muscle group to perform repeated contractions or sustain a contraction over an extended period
  • Improves with training due to increased mitochondrial density, capillarization, and oxidative enzyme activity
• Delayed onset muscle soreness (DOMS) is the pain and stiffness felt in muscles several hours to days after unaccustomed or strenuous exercise
  • Caused by microscopic damage to muscle fibers and inflammation
  • Gradually subsides as the muscle adapts and recovers

Exercise Testing Methods

• Graded exercise testing (GXT) involves progressively increasing the workload on a treadmill or cycle ergometer while monitoring physiological responses
  • Used to assess cardiovascular fitness (VO2 max), identify exercise-induced abnormalities, and prescribe exercise
  • Protocols include Bruce, Balke, and Astrand-Rhyming
• Submaximal exercise testing estimates VO2 max without requiring maximal effort
  • Examples include the Astrand-Rhyming cycle ergometer test and the Rockport 1-mile walk test
  • Relies on the linear relationship between heart rate and oxygen uptake at submaximal intensities
• Muscular strength testing evaluates the maximum force a muscle or muscle group can generate
  • 1 repetition maximum (1RM) is the heaviest weight that can be lifted once with proper form
  • Dynamometers (handgrip, isokinetic) measure force output under specific conditions
• Muscular endurance testing assesses the ability to perform repeated contractions or sustain a contraction over time
  • Examples include push-up, sit-up, and plank tests
  • Repetitions completed or time to fatigue are common measures
• Flexibility testing measures the range of motion around a joint or series of joints
  • Sit-and-reach test is a common field test for assessing hamstring and lower back flexibility
  • Goniometers are used for more precise measurements of joint angles

Prescription Principles and Guidelines

• FITT principle guides exercise prescription based on Frequency, Intensity, Time, and Type
  • Frequency: Number of exercise sessions per week (3-5 for most individuals)
  • Intensity: Level of effort or workload (% of VO2 max, % of 1RM, RPE)
  • Time: Duration of each exercise session (20-60 minutes for cardiovascular, 30-60 minutes for resistance)
  • Type: Mode of exercise (walking, cycling, resistance training, etc.)
• Specificity principle states that physiological adaptations are specific to the type of training performed
  • Cardiovascular training improves cardiovascular fitness, while resistance training enhances strength and muscle size
  • Training should be specific to the individual's goals and needs
• Progressive overload involves gradually increasing the stress placed on the body during exercise to continually adapt and improve
  • Can be achieved by increasing frequency, intensity, time, or resistance
  • Allows for continued improvement and minimizes the risk of injury
• Reversibility principle states that physiological adaptations are lost when training is discontinued or reduced
  • Also known as detraining, which can occur within 2-4 weeks of stopping exercise
  • Maintaining a consistent exercise routine is essential for preserving fitness gains
• Periodization is the systematic planning of exercise training to optimize performance and prevent overtraining
  • Involves cycles of progressive overload and recovery
  • Can be linear (gradual increase in load) or undulating (varying load and volume)

Special Populations and Considerations

• Older adults may require modifications to exercise prescription due to age-related changes in physiology and increased risk of chronic diseases
  • Focus on functional fitness, balance, and flexibility to maintain independence and reduce fall risk
  • Lower-intensity, longer-duration aerobic exercise and moderate-intensity resistance training are generally well-tolerated
• Children and adolescents have unique physiological and psychological needs when it comes to exercise
  • Emphasis should be on fun, variety, and skill development rather than competition or intense training
  • Resistance training can be safe and effective when properly supervised and progressively overloaded
• Pregnancy requires special considerations for exercise prescription to ensure the safety of the mother and fetus
  • Low to moderate-intensity aerobic exercise is generally safe and beneficial for healthy pregnancies
  • Avoid high-impact, contact sports, and exercises that involve lying supine after the first trimester
• Individuals with chronic diseases (cardiovascular disease, diabetes, obesity) can benefit from regular exercise but may require modifications
  • Medical clearance and/or exercise stress testing may be necessary before starting an exercise program
  • Prescribed exercise should take into account the individual's medications, symptoms, and disease management
• Environmental factors such as heat, cold, and altitude can affect exercise performance and safety
  • Heat stress can lead to dehydration, heat exhaustion, and heat stroke; precautions include proper hydration, acclimatization, and adjusting exercise intensity
  • Cold stress can increase the risk of hypothermia and frostbite; appropriate clothing and avoiding extreme conditions are important
  • Altitude exposure can reduce oxygen availability and affect exercise performance; gradual acclimatization and reduced exercise intensity may be necessary