Principle of Exercise Physiology PDF

Principle of Exercise Physiology PIO 211 Ibrahim Musa, Ph.D. Department of Human Physiology, Faculty of Basic Medical Sciences, Prince Abubakar Audu University, Anyigba.  Course Outline for PIO211  Introduction to Exercise Physiology:  Energy Systems and Me...

Principle of Exercise Physiology PIO 211 Ibrahim Musa, Ph.D. Department of Human Physiology, Faculty of Basic Medical Sciences, Prince Abubakar Audu University, Anyigba.  Course Outline for PIO211  Introduction to Exercise Physiology:  Energy Systems and Metabolism  Cardiorespiratory Function:  Neuromuscular Function:  Endocrine Responses to Exercise:  Temperature Regulation and Fluid Balance:  INTRODUCTION  The term “Exercise Physiology ” implies the study of how the body organ systems responds and adjust to physical activity.  It helps us to understand how physical activity prevent/reverse diseases, improves fitness, strength, and overall well-being.  An exercise physiologist's field of study covers a wide range of disciplines, including biochemistry, cardiopulmonary physiology, hematology, skeletal muscle physiology, neuroendocrine physiology, and neurophysiology  The two main branches of exercise physiology are clinical and sports exercise physiology:  Clinical exercise physiology: Helps people with chronic illness or reduced mobility.  Sports exercise physiology: Works with athletes to specialize in how the body responds to exercise  Energy Systems and Metabolism During Exercise  Energy systems refer to the specific mechanisms in which energy (ATP) is produced and used by the body.  ATP: Adenosine triphosphate  The availability of ATP is critical for the activity of key enzymes involved in:  membrane excitability (Na+/K+ ATPase),  sarcoplasmic reticulum calcium handling (Ca2+ ATPase) and  myofilament cross-bridge cycling (myosin ATPase).  During exercise, the body relies on three primary energy systems to produce ATP  the phosphagen, glycolytic, and oxidative pathways.  Phosphagen System (ATP-PC System):  Primary Fuel: Stored adenosine triphosphate (ATP) and phosphocreatine (PCr).  Duration: Provides energy for very short, high-intensity activities (e.g., sprinting or weightlifting) lasting up to 10 seconds.  Characteristics: Fastest energy production but limited supply; anaerobic (does not require oxygen).  Glycolytic System (Anaerobic Glycolysis):  Primary Fuel: Glucose and glycogen.  Duration: Supports moderate-to-high intensity activities lasting 10 seconds to about 2 minutes (e.g., 400-meter run).  Characteristics: Produces energy without oxygen, resulting in the formation of lactate, which can lead to muscle fatigue.  Oxidative System (Aerobic Metabolism):  Primary Fuel: Primarily carbohydrates and fats; proteins contribute minimally under normal conditions.  Duration: Dominates during low-to-moderate intensity activities lasting over 2 minutes (e.g., marathon running).  Characteristics: Slower ATP production but sustainable over long periods; requires oxygen and supports recovery from anaerobic exercise.  Together, these systems ensure a continuous ATP supply, adapting to the intensity and duration of physical activity  Cardiorespiratory Function During Exercise  Muscular exercise involves a significant increase in metabolic demand, requiring efficient function of both the cardiovascular and respiratory systems.  Together, these systems ensure adequate oxygen delivery to working muscles and the removal of metabolic by-products such as carbon dioxide.  The Role of the Cardiovascular System in Exercise  The cardiovascular system adapts to meet the increased oxygen and nutrient demands of active muscles  Cardiorespiratory Function Cont  Key variables include: cardiac output, distribution of blood, & blood pressure  1 Cardiac Output (CO)  Definition: The volume of blood pumped by the heart per minute.  It depends on: 1. Heart Rate (HR): The number of times the heart beats per minute. 2. Stroke Volume (SV): The volume of blood the heart pumps out with each beat.  Formula: Cardiac Output (CO)=HR×SV  So, if the heart beats faster (higher HR) or pumps more blood per beat (higher SV), the cardiac output increases. Rest vs. Exercise: At rest: ~5 L/min During intense exercise: Up to 25-30 L/min in trained athletes.  Cardiorespiratory Function Cont  2 Redistribution of Blood Flow Rest: ~15-20% of cardiac output goes to muscles. Exercise: Up to 85% of cardiac output is directed to active muscles.  Mechanisms: Vasodilation in working/Active muscles. Vasoconstriction in less active regions (e.g., digestive organs).  3 Blood Pressure (BP): is the force of blood pushing against the walls of the blood vessels as the heart pumps blood around the body.  It has two main numbers: Systolic pressure (higher number): The pressure when the heart squeezes and pumps blood. Diastolic pressure (lower number): The pressure when the heart relaxes between beats. For example, if the blood pressure is 120/80 mmHg, 120 is the systolic pressure, and 80 is the diastolic pressure.  Cardiorespiratory Function Cont  Dynamic exercise: Systolic BP increases due to higher cardiac output, while diastolic BP remains stable or slightly decreases.  Isometric exercise: Both systolic and diastolic BP increase significantly.  Dynamic Exercise: Involves movement, where muscles shorten and lengthen repeatedly (like running, swimming, or cycling).  Blood flow increases due to alternating contraction and relaxation of muscles.  Isometric Exercise: No visible movement; muscles contract but stay the same length (like holding a plank or pushing against a wall).  Blood flow is restricted because the muscles stay tense continuously.  Cardiorespiratory Function Cont  The Role of the Respiratory System in Exercise  The respiratory system ensures an adequate exchange of oxygen (O2) and carbon dioxide (CO2) to support metabolic needs.  1 Ventilation (VE) Definition: The movement of air in and out of the lungs per minute.  It depends on:  Breathing rate: The number of breaths per minute.  Tidal volume: the volume of air breathe in with each breath.  Ventilation increases during exercise to supply the body with more oxygen and get rid of more carbon dioxide.  Cardiorespiratory Function Cont  The formula is: 𝑉𝐸=Breathing rate × Tidal volume  For example, if one takes 12 breaths per minute and each breath moves 500 mL of air, the ventilation is 6,000 mL/min (6 L/min).  Rest vs. Exercise: Rest: ~6-8 L/min During intense exercise: Up to 100-200 L/min.  Cardiorespiratory Function Cont  2 Oxygen Uptake (VO2) Definition: The volume of oxygen consumed by the body per minute.  VO2max: The maximum rate of oxygen consumption, indicating aerobic fitness. Higher VO₂max levels are associated with healthy heart and longer life expectancy.  Determined by cardiac output and the arteriovenous oxygen difference  Influenced by factors such as  Age: VO₂max declines with age, typically after age 30.  Sex: Males often have higher VO₂max values due to larger hearts and more muscle mass.  Fitness Level: Regular aerobic exercise can significantly improve VO ₂max.  Genetics: Some people are naturally more efficient at using oxygen.  Altitude: Training at higher altitudes can improve VO ₂max by increasing red blood cell counts  Cardiorespiratory Function Cont.  Integration of Cardiorespiratory Responses  1 Anticipatory Response: (Before exercise) the heart rate and ventilation increase due to sympathetic nervous system activation.  2 Acute Responses Heart Rate (HR): Increases linearly with exercise intensity. Stroke Volume (SV): Increases at moderate intensities but plateaus at higher intensities.  Ventilation: Low to moderate intensity: Linear increase. High intensity: Exponential rise due to increased metabolic acidosis (ventilatory threshold).  Cardiorespiratory Function Cont.  Recovery Post-exercise, HR and ventilation decrease gradually to baseline levels. Influenced by fitness level, exercise intensity, and duration.  Energy and Oxygen Delivery 1. Oxygen Transport Cascade Lungs: Oxygen enters the blood through alveolar gas exchange. Blood: Hemoglobin transports oxygen to tissues. Muscles: Mitochondria use oxygen for ATP production. 2. Lactate Threshold  The point at which lactate production exceeds clearance, indicating a shift to anaerobic metabolism.  Training can increase the threshold, delaying fatigue.  Cardiorespiratory Function Cont.  Long-Term Adaptations to Exercise  Regular exercise leads to improvements in cardiorespiratory efficiency: Heart: Increased stroke volume and reduced resting HR. Lungs: Enhanced lung capacity and respiratory muscle efficiency. Muscles: Improved capillary density and mitochondrial function.  Clinical Applications  Understanding cardiorespiratory function during exercise is crucial in: Designing training programs for athletes. Managing chronic diseases (e.g., cardiovascular disease, COPD). Rehabilitation programs for post-surgery or injury recovery.  Neuromuscular Function During Exercise  Neuromuscular function refers to the interaction between the nervous system and muscles to produce movement.  During exercise, this interaction becomes more complex and dynamic, involving increased motor unit recruitment, enhanced neuromuscular transmission, and adaptations in energy metabolism.  Understanding these processes is essential to grasp how the body responds to physical stress and maintains homeostasis.  Physiologic Anatomy of the Neuromuscular 1.Components of the Neuromuscular System o Central Nervous System (CNS): Brain and spinal cord regulate voluntary and reflexive muscle actions. o Peripheral Nervous System (PNS): Motor neurons transmit signals from the CNS to muscles. o Motor Unit: A single motor neuron and all the muscle fibers it innervates. o Neuromuscular Junction (NMJ): A synapse where motor neuron terminals release acetylcholine (ACh) to activate muscle fibers.  Physiologic Anatomy of the Neuromuscular COTN. 2. Muscle Contraction o Signal travels as an action potential from the CNS to the motor neuron. o At the NMJ, ACh binds to receptors on the muscle membrane, triggering depolarization. o The action potential spreads through the sarcolemma and down the T-tubules, activating the release of calcium from the sarcoplasmic reticulum. o Calcium binds to troponin, shifting tropomyosin to expose myosin-binding sites on actin filaments. o Myosin heads bind to actin, perform power strokes using ATP, and generate force.  Neuromuscular Response to Exercise  1. Recruitment of Motor Units  Size Principle: Smaller motor units (slow-twitch fibers) are recruited first, followed by larger units (fast-twitch fibers) as intensity increases.  Low-Intensity Exercise: Activates slow-twitch (Type I) fibers that are fatigue-resistant and use oxidative metabolism.  High-Intensity Exercise: Involves fast-twitch (Type II) fibers, which generate greater force but fatigue quickly due to reliance on anaerobic metabolism.  2. Neuromuscular Transmission  Increased synaptic activity at the NMJ to meet the demand for rapid and sustained contractions.  Neuromuscular Response to Exercise COTN.  2. Neuromuscular Transmission  Increased synaptic activity at the NMJ to meet the demand for rapid and sustained contractions.  Enhanced release of ACh and greater sensitivity of muscle fibers to depolarization.  Fatigue during prolonged exercise may result from depletion of ACh or receptor desensitization.  Neuromuscular Response to Exercise COTN.  3. Muscle Fiber Adaptations During Exercise  1. Acute Changes Increased Blood Flow: Enhanced perfusion delivers oxygen and nutrients to active muscles. Metabolic Changes: ATP is rapidly consumed and regenerated through pathways like glycolysis, oxidative phosphorylation, and creatine phosphate. Lactate accumulates during anaerobic exercise but is cleared during recovery.  2. Chronic Changes (Adaptation)  Neuromuscular Response to Exercise COTN.  2. Chronic Changes (Adaptation) Endurance Training:  Increases mitochondrial density and capillary supply to muscle fibers.  Enhances Type I fiber function and fatigue resistance. Resistance Training:  Leads to hypertrophy (growth) of Type II fibers and increased motor unit synchronization.  Improves neuromuscular coordination and force production.  Neuromuscular Response to Exercise COTN.  2. Chronic Changes (Adaptation) Endurance Training:  Increases mitochondrial density and capillary supply to muscle fibers.  Enhances Type I fiber function and fatigue resistance. Resistance Training:  Leads to hypertrophy (growth) of Type II fibers and increased motor unit synchronization.  Improves neuromuscular coordination and force production.  Neuromuscular Response to Exercise COTN.  4. Neuromuscular Fatigue Fatigue is a decline in the muscle's ability to generate force and can result from:  1. Central Fatigue: Reduced CNS drive to motor neurons due to decreased motivation or inhibitory signals. Common in prolonged exercise.  2. Peripheral Fatigue:  Depletion of energy stores (ATP, glycogen).  Accumulation of metabolites (e.g., H+) interferes with calcium release and cross-bridge cycling.  Impaired NMJ transmission due to ACh depletion.  Neuromuscular Response to Exercise COTN.  5. Practical Applications 1. Exercise Prescription: Tailored exercise programs enhance neuromuscular health and prevent age-related decline. 2.Rehabilitation: Neuromuscular electrical stimulation (NMES) aids in recovering strength in patients with neuromuscular dysfunction. 3.Sports Performance: Optimizing motor unit recruitment and coordination improves athletic performance.  Endocrine Responses to Exercise:  The endocrine system plays a crucial role in regulating physiological responses during and after muscular exercise.  It achieves this by secreting hormones that influence energy metabolism, cardiovascular function, fluid balance, and recovery.  Hormonal Regulation During Exercise  Exercise is a stressor that triggers a complex hormonal response to maintain homeostasis.  The key hormones involved are: Stress Hormones, Catecholamines (Adrenaline and Noradrenaline), Growth Hormone (GH), Insulin and Glucagon, Endorphins, Thyroid Hormones (T3 and T4), Sex Hormones,  1. Stress Hormones (Cortisol):  Secreted by the adrenal cortex  Stimulated by the hypothalamic-pituitary-adrenal (HPA) axis.  Increases during prolonged or intense exercise. Functions:  Promotes gluconeogenesis in the liver.  Mobilizes amino acids from muscle.  Increases lipolysis for energy availability.  Acts as an anti-inflammatory agent but can suppress the immune system with prolonged elevation. Chronic elevation may impair recovery.  2. Catecholamines (Adrenaline and Noradrenaline):  Secreted by the adrenal medulla.  Rapid response to exercise (fight-or-flight hormones). Functions: Increase heart rate and blood pressure. Enhance glycogenolysis and lipolysis in the liver and muscle to provide immediate energy. Mobilize fatty acids for energy.   3. Growth Hormone (GH): Released by the anterior pituitary gland. Peaks during high-intensity exercise. Functions: Stimulates lipolysis. Promotes muscle repair and growth.  4. Insulin and Glucagon:  Secreted by the pancreas  Insulin levels decrease during exercise to reduce glucose uptake by non-exercising tissues.  Glucagon secretion increases, promoting glycogenolysis and gluconeogenesis to maintain blood glucose levels.  Combined action ensures stable blood glucose levels.   5. Endorphins:  Released from the pituitary gland.  Functions: Provide pain relief. Improve mood (exercise-induced euphoria).  6. Thyroid Hormones (T3 and T4):  Released from the thyroid gland  Increase basal metabolic rate.  Enhance the effects of catecholamines.  7. Sex Hormones: secreted by the gonads  Testosterone:  Increases during resistance exercise.  Enhances protein synthesis and muscle growth.  Oestrogen:  Contributes to fat metabolism and recovery processes.  Gender Differences in Hormonal Responses  Women:  Oestrogen and progesterone influence energy metabolism and thermoregulation.  Hormonal fluctuations during the menstrual cycle can affect performance and recovery.  Men:  Higher baseline testosterone levels contribute to greater muscle hypertrophy and strength gains.  Exercise Type and Hormonal Response 1. Aerobic Exercise: Sustained moderate-intensity exercise. Gradual increases in cortisol and catecholamines Predominantly uses fatty acids for energy. 2. Anaerobic/Resistance Exercise:  Short bursts of high-intensity exercise.  Significant increase in GH, testosterone, and catecholamines.  Focus on glycogen breakdown and muscle repair post-exercise.  Post-Exercise Hormonal Changes  Recovery Phase: o Cortisol returns to baseline if recovery is adequate. o GH levels remain elevated to facilitate repair. o Insulin sensitivity improves in muscle tissue, aiding glycogen replenishment.  Endorphins contribute to post-exercise relaxation and mood elevation.  Adaptations to Exercise  With regular training, the endocrine system adapts:  Improved efficiency of hormone release and receptor sensitivity.  Reduced resting levels of cortisol and catecholamines.  Enhanced anabolic response, favouring muscle growth and recovery.  Post-Exercise Hormonal Effects Anabolic Hormones:  Growth hormone, IGF-1, and testosterone levels increase post-exercise, promoting muscle repair and hypertrophy.  Insulin sensitivity improves, facilitating glycogen and protein synthesis. Stress Hormones:  Cortisol levels gradually normalize, but prolonged elevation (overtraining) can impair recovery and immune function.  Clinical Implications  Understanding these responses helps optimize:  Training regimens tailored to individual goals (e.g., strength vs. endurance).  Nutritional strategies to support recovery and performance.  Interventions to prevent overtraining and hormonal imbalances.  Temperature Regulation and Fluid Balance  Exercise generates heat and causes fluid loss through sweat and respiration.  Maintaining temperature and fluid balance is critical for performance and safety.  Homeostasis of body temperature and fluid levels ensures efficient metabolic and muscular function during exercise.  Exercise generates heat as muscles work, raising body temperature.  Excess heat must be removed to avoid overheating, which can impair performance and cause heat-related illnesses.  Temperature Regulation During Exercise  Heat Production: Sources of Heat:  Muscle contractions: Exercise increases muscle contractions, which generate heat as a by-product of energy metabolism. Muscular contraction is only ~20-25% efficient; the remaining energy is released as heat.  Metabolism: The breakdown of ATP for muscle activity is an exothermic process, leading to heat production  Intensity of exercise correlates with the rate of heat production. Core Temperature:  Resting core temperature: ~37°C (98.6°F).  Can rise to >40°C during intense exercise.  Main Heat Dissipation Mechanisms During Exercise  The human body employs several physiological mechanisms to regulate temperature and dissipate excess heat during exercise: 1. Evaporation: 1. Sweating is the primary mechanism for heat loss during exercise, especially in hot environments. 2. As sweat evaporates from the skin surface, it removes heat, cooling the body. 2. Convection: 1. Heat is transferred from the skin to the surrounding air. Movement, such as running or a breeze, enhances this process by replacing warm air with cooler air. 3. Radiation: 1. The body emits infrared radiation to the environment if the ambient temperature is lower than the skin temperature. 4. Conduction: 1. Direct heat transfer occurs through physical contact with cooler surfaces, such as water or equipment. Physiological Responses to Heat Stress 1.Thermoregulatory Centers: 1. The hypothalamus acts as the central regulator by detecting changes in core and skin temperatures via thermoreceptors. 2. It initiates responses to promote heat dissipation or conservation as needed.  Factors Affecting Temperature Regulation During Exercise  Fitness Level: Well-trained individuals have more efficient thermoregulatory responses.  Hydration Status: Excessive sweating without adequate fluid replacement leads to dehydration, impairing thermoregulation. Dehydration impairs sweating and blood flow to the skin.  Body Composition: Higher body fat may act as insulation, reducing heat loss.  Environmental Conditions: High temperature and humidity reduce the effectiveness of heat loss. Prolonged exercise in hot environments can lead to heat exhaustion or heat stroke if cooling mechanisms fail.  Clothing: Breathable materials enhance heat loss.  Acclimatization: Gradual exposure to hot environments improves the body’s ability to regulate temperature through adaptations like increased sweat rate and earlier onset of sweating.  Optimizing Temperature Regulation During Exercise  Hydration: Drink water or electrolyte solutions before, during, and after exercise.  Clothing: Wear lightweight and breathable fabrics.  Timing: Avoid exercising during the hottest parts of the day.  Environment: Use fans or cool spaces to enhance convection and evaporation.  Fluid Regulation During exercise  Fluid balance is critical for maintaining physiological function during exercise.  This understanding is essential for healthcare professionals to guide athletes and manage exercise-associated conditions effectively. Fluid Dynamics During Exercise  Increased Sweat Loss: Exercise induces sweating for thermoregulation, leading to significant fluid loss.  Sweat contains water and electrolytes (primarily sodium and chloride, with smaller amounts of potassium, calcium, and magnesium).  Respiratory Fluid Loss: Increased respiratory rate during exercise contributes to water loss through exhalation.  Shift in Fluid Compartments: Redistribution of blood flow to active muscles and the skin reduces plasma volume.  Dehydration Symptoms: Fatigue, dizziness, increased heart rate, and reduced exercise performance  Fluid Regulatory Mechanisms During exercise  The body uses several mechanisms to regulate fluid balance during exercise:  A. Hormonal Responses 1. Antidiuretic Hormone (ADH): 1. Released by the posterior pituitary in response to increased plasma osmolality. 2. Promotes water reabsorption in the kidneys to conserve fluid. 2. Aldosterone: 1. Secreted by the adrenal cortex in response to low sodium or blood volume. 2. Enhances sodium reabsorption and potassium excretion in the kidneys. 3. Renin-Angiotensin-Aldosterone System (RAAS): Activated during exercise-induced hypovolemia to conserve sodium and water.  Fluid Regulatory Mechanisms During exercise CONT.  B. Cardiovascular Adjustments Maintenance of cardiac output compensates for reduced plasma volume.  C. Thirst Mechanism Controlled by osmoreceptors in the hypothalamus. Increased plasma osmolality and hypovolemia stimulate thirst to promote fluid intake.  Maintaining Fluid Balance During Exercise  A. Pre-Exercise Hydration Drink 500–600 mL of water or sports drink 2–3 hours before exercise. Ensure normal hydration status prior to starting.  B. During Exercise Water is typically sufficient for hydration.  C. Post-Exercise Rehydration Replace 1.5 times the fluid lost during exercise to account for ongoing losses. Include sodium in post-exercise fluids to restore electrolyte balance and aid fluid retention.  D. Monitoring Hydration Status Urine Colour: Pale yellow indicates adequate hydration. Body Weight: Measure pre- and post-exercise weight to estimate fluid loss. 1 kg of weight loss = ~1 litre of fluid loss.