BIOENERGETICS OF TRAINING; ENDOCRINE RESPONSE PEP 3136: Exercise Leadership II Dr. Michael Hartman, CSCS*D Introduction: Metabolism Total of all chemical reactions that occur in the body Anabolic reactions Synthesis of molecules Catabolic reactions Breakdown of molecules Bioenergetics Converting food nutrients (fats, proteins, carbohydrates) into energy Nutrients: Energy supply for the body There are different nutrients used to produce energy for metabolism Carbohydrates: 4 kcal/g Fat: 9 kcal/g Protein: 4.1 kcal/g Carbohydrates (CHO) can be metabolized under aerobic and anaerobic conditions Proteins and fat require oxygen to be metabolized Nutrients: Energy storage Carbohydrates Glucose Stored as glycogen Fats Primarily fatty acids Stored as triglycerides Proteins Amino acids Not a primary energy source Bioenergetics: ATP The chemical energy produced from nutrient sources, used as a universal cellular energy, is adenosine triphosphate (ATP). ATP consists of adenine, a 5-carbon sugar called ribose, and three linked phosphates, symbolized by Pi (inorganic phosphate). adenine NH2 N N O O O HO P O P O P O N N O OH OH OH triphosphate OH OH ribose Bioenergetics: ATP Energy stored in the chemical bonds of adenosine triphosphate (ATP) is used to power muscular activity. The replenishment of ATP in human skeletal muscle is accomplished by three basic energy systems: Phosphagen (ATP-PCr) Glycolytic Oxidative Bioenergetics: ATP Formation of ATP Phosphocreatine (PC) breakdown Degradation of glucose and glycogen (glycolysis) Oxidative formation of ATP Anaerobic pathways Does not involve O2 PC breakdown and glycolysis Aerobic pathways Requires O2 Oxidative phosphorylation Bioenergetics: ATP Breakdown: ATP ATPase ADP + Pi + Energy Formation: ADP + Pi ATP work synthesis mechanical transport Energy Systems: The different energy systems of the human body are used regarding to different energetic demands •Phosphagen (ATP-PCr) •Glycolysis •Oxidative Energy Usage: In general, an inverse relationship exists between the relative rate and total amount of ATP that a given energy system can produce. As a result, the phosphagen energy system primarily supplies ATP for high-intensity activities of short duration, the glycolytic system for moderate- to high-intensity activities of short to medium duration, and the oxidative system for low-intensity activities of long duration. Energy Usage: Duration Intensity Primary Energy System(s) 0-10 s Very intense Phosphagen 11-30 s Intense Phosphagen and Fast Glycolysis 30 s-2 min Heavy Fast Glycolysis 2-3 min Moderate Fast Glycolysis and Oxidative System > 3 min Light Oxidative System Energy production: System Rate of ATP Capacity of ATP Phosphagen 1 5 Fast glycolysis 2 4 Slow glycolysis 3 3 Oxidation (CHO) 4 2 Oxidation (FAT, PRO) 5 1 1 = fastest/greatest; 5 = slowest/least Energy Usage: The extent to which each of the three energy systems contributes to ATP production depends primarily on the intensity of muscular activity and secondarily on the duration. At no time, during either exercise or rest, does any single energy system provide the complete supply of energy. Aerobic vs. Anaerobic Energy: Energy to perform exercise comes from an interaction between aerobic and anaerobic pathways Exercise intensity is the most important variable related to which energy system is activated to produce ATP for muscular work Effect of Duration and Intensity Short-term, high-intensity activities Greater contribution of anaerobic energy systems Long-term, low to moderate-intensity exercise Majority of ATP produced from aerobic sources Endocrine Response Introduction: It has been theorized that the endocrine system can be manipulated naturally with resistance training to enhance the development of various target tissues, thereby improving performance. Endocrine Glands: Secrete substances (hormones) into blood or body fluid; Promotes homeostasis; Tissue adaptations are related to endocrine responses to exercise Hormones function in reproduction; growth and development; energy production, utilization, and storage; immunity Peptide hormones (protein)- indirectly effects cell function by binding to a hormone receptor Steroid hormones (fat)- directly effect the DNA in the nucleus of a cell Hormonal Response to Heavy Resistance Training Hormonal secretions related to Amount and type of stress Metabolic demands of exercise Changes in resting metabolism Hormonal response occurs only in tissue exercised Mechanisms of Hormone Interaction Increased concentration of hormones facilitates interaction Recoveryfrom anaerobic exercise promotes cell growth (anabolism) Inappropriate exercise prescriptions can result in a net catabolic effect Hormones Vital to Exercise Testosterone Cortisol Growth hormone Insulin and glucagons Epinephrine Norepinephrine Testosterone Steroid hormone Produced primarily by the Leydig cells in the male testes Regulated by the hypothalamic-pituitary axis Testosterone (cont.) Circulating testosterone in females is about 10% of that in males and comes from the ovaries and the adrenal cortex During maturation, testosterone contributes to many of the male sexual characteristics associated with development Cortisol Steroid hormone Secreted by the outer layer of the adrenal glands Sometimes called stress hormone Ensures availability of energy by increasing production of glucose, decreasing glucose uptake, increasing glycogen production in skeletal muscle, and causing amino acids to be mobilized from skeletal muscle Growth Hormone Polypeptide hormone Consists of 191 amino acids and two disulfide bonds Produced and secreted from the anterior pituitary gland Many variations exist Growth Hormone (cont.) Associated with growth properties Exerts tremendous influence on the metabolic system and energy availability Increases muscle uptake of amino acids as well as the breakdown of lipids via lipolysis Insulin and Glucagons Insulin – 51 amino acid peptide hormone – Produced by the beta cells of the pancreas – Consists of a 21-amino acid A-chain and a 30- amino acid B-chain connected by two disulfide bonds Glucagon – Polypeptide chain 29 amino acids long – Produced by the alpha cells of the pancreas Insulin and Glucagons (cont.) Both are released in response to increasing or decreasing blood glucose levels Both are under control by epinephrine and norepinephrine from the sympathetic nervous system, causing insulin to decrease and glucagon to increase Epinephrine Sometimes called adrenaline An amine neurohormone Serves as a neurotransmitter in the central nervous system and transmits signals between the synapses of nerve cells Epinephrine (cont.) Plays a big role in the circulation by interacting with a variety of alpha and beta receptors in many different tissues in the body Responsible for many of the “fight-or-flight” responses Norepinephrine Also known as noradrenaline An amine neurohormone Comes from spillover from sympathetic nervous system synapses Sometimes considered an indicator of sympathetic nervous system activity Acute and Chronic Training Adaptations Regular training and physical activity result in an adaptation of the body to accommodate stresses on the body Up-regulation: refers to an increase in the number of receptors on the surface of target cells, making the cells more sensitive to a hormone or other molecule Down-regulation: a decrease in the number of receptors on the surface of target cells, making the cells less sensitive to a hormone or other molecule The Hormonal System and Acute Responses to Resistance Exercise Acute Training Variables for Resistance Training 1. Choice of exercise 2. Order of exercise 3. Volume of exercise 4. Intensity (or load) of exercise 5. Inter-set rest intervals Key Point During heavy resistance exercise, the specific hormonal response is dependent in large part on the five acute training variables. Acute Response to Resistance Exercise Testosterone: responds most when large-muscle- mass, multi-joint exercise are performed and when high-power exercises are used Cortisol: responds much like testosterone but exhibits a larger acute response to resistance exercise Growth hormone: responds like testosterone and cortisol but may produce a larger response from the use of free weights than machine exercises Key Point Long-term hormonal adaptations to training are more subtle than the acute response to a single session, but they can provide an important training adaptation. Overtraining Overtraining: The only way to continue to improve exercise performance with training is to progressively increase the training stress. However, when this concept is carried too far, pushing the body beyond its ability to adapt, the training may became excessive. Overtraining: Overtraining is an imbalance between exercise and recovery in which the athlete’s training program execeeds the body’s physiologic and psycologic limits and causes fatigue and reduced functional capacity. This problem results from a short to medium-term increase in training volume and/or intensityover the athlete’s previously substantial baseline. Overtraining An increase in training volume and/or intensity (training load) resulting in performance decrements Associated with chronic overwork or long-term training stress Overtraining Normal Response to Training Potential for Overtraining Verhoshansky, Y.V. (1986) Fundamentals of Special Strength Training in Sport Overtraining OVERTRAINING SYNDROME Overload Fatigue Overreaching Overtraining Overtraining: Overload necessary stimulus needed to improve Fatigue normal response to training Overreaching short-termovertraining (less than 4 weeks) sometimes planned Developement of Overtraining Physical factors Emotional factors : Demands of competition Desire to win Fear of failure OVERTRAINING Unrealistically high goals Decline in performance accompained by a loss in competitive desire and a loss in enthusiasm for training Developement of Overtraining Physical factors Too intense Too high Excessive training Training load Training volume Overcaming the body’s ability of recovering and adapting Overtraining Catabolism > Anabolism syndrome Overtraining and the Endocrine System Overtraining occurs when training volume and/or intensity is excessive and results in prolonged decreases in performance It has been suggested that monitoring certain hormones may permit monitoring of the training stresses, thus avoiding the onset of an overtrained state Changes in hormone blood levels during a period of intensified training Recovery: Recovery from overtraining syndrome is only possible with a marked reduction in training intensity or complete rest. The best way to minimize the risk of overtraining is to follow cycling training procedures, alternating easy, moderate and hard periods of training. Periodization Overtraining Prolonged Recovery Recovery period need in excess of 2-weeks Can last up to 1-year Resistance Exercise: CR Adaptations CR Adaptations: Regular physical activity can improve cardiovascular fitness and may reduce the likelihood and debilitating effects of cardiovascular disease. Weight-training has generally been believed to have limited value in modifying risks of cardiovascular disease. CR Adaptations: Acute aerobic exercise results in increased cardiac output, stroke volume, heart rate, oxygen uptake, systolic blood pressure, and blood flow to active muscles and a decrease in diastolic blood pressure. Resistance exercise with low intensity and high volume generally results in similar responses, some to a lesser degree. CR Adaptations: Aerobic exercise training results in increased maximal cardiac output and maximal oxygen uptake, slower resting heart rate, increased capillarization, improved ventilation efficiency, increased oxygen extraction, and OBLA occurring at a higher percentage of aerobic capacity. CR Adaptations: Acute bouts of high-intensity, low-volume resistance exercise result in increased heart rate and increased diastolic and systolic blood pressure but no change in oxygen uptake, no change or a slight increase in cardiac output, and no change or a slight decrease in stroke volume.
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