Nutrition in Sports and Fitness PDF

Nutrition in Sports and Fitness HUMAN ENERGY REQUIREMENTS FOR EXERCISE Learning Outcomes Understand what is Sports Nutrition Discuss the importance of nutrients for Athletes Identify the components of energy expenditure Assess energy expenditure using different techniques Discuss the major human en...

Nutrition in Sports and Fitness HUMAN ENERGY REQUIREMENTS FOR EXERCISE Learning Outcomes Understand what is Sports Nutrition Discuss the importance of nutrients for Athletes Identify the components of energy expenditure Assess energy expenditure using different techniques Discuss the major human energy systems Deduce the sources of energy for various sporting activities Explain the occurrence of fatigue during exercise Introduction: What is Sports Nutrition Sports nutrition is a specialization within the field of nutrition ◦ Defined as the application of nutrition knowledge to a practical daily eating plan focused on: ◦ providing the fuel for physical activity, facilitating the repair and rebuilding process following hard physical work, and optimizing athletic performance in competitive events Athlete refers to any individual who is regularly active ◦ ranging from the fitness enthusiast to the competitive amateur or professional Sports Nutrition The field of sports nutrition requires: ◦ a command of general nutrition and exercise science ◦ an understanding of their interrelationship, and ◦ the knowledge of how to practically apply sports nutrition concepts The Basic Nutrients Foods and beverages are composed of six nutrients that are vital to the human body for: ◦ producing energy, ◦ contributing to the growth and development of tissues, ◦ regulating body processes, and ◦ preventing deficiency and degenerative diseases The six nutrients are carbohydrates, proteins, fats, vitamins, minerals, and water Nutrients in Performance The Energy Nutrients Carbohydrates, proteins, and fats serve as the body’s source of energy ◦ are considered the energy nutrients Adenosine triphosphate (ATP) ◦The molecule that serves as the body’s direct source of energy for cellular work. Nutrition for Athlete Appropriate energy intake is the cornerstone of the athlete’s diet An athlete’s energy requirements depend on: ◦the periodized training and competition cycle ◦ varies from day to day throughout the yearly training plan relative to changes in training volume and intensity Energy Balance Energy balance: total energy intake (EI) = total energy expenditure (TEE) Energy intake is the sum of the energy in all food and beverages consumed Energy output is more complex and is described through the components of total energy expenditure Energy Expenditure Energy expenditure consists of: ◦ basal metabolic rate (BMR) ◦ the thermic effect of food (TEF) ◦ the thermic effect of activity (TEA) TEE = BMR + TEF +TEA TEA = Planned Exercise Expenditure + Spontaneous Physical Activity + Nonexercise Activity Thermogenesis Components of Energy Expenditure Basal Metabolic Rate and Resting Energy Expenditure ◦ Expenditure for respiration, heartbeat, renal function, blood circulation ◦ Measured in person in postabsorptive state, supine, motionless, thermoneutral environment ◦ BMR accounts for about 50%-70% of daily total energy expenditure ◦ RMR is thought to account for about 65%-80% of daily total energy expenditure. Thermic effect of food ◦ Protein increases expenditure 20%-30% ◦ CHO: 5%-10% ◦ Fat: 0%-5% Measuring BMR/RMR Components of Energy Expenditure Energy expenditure of physical activity ◦ Physical activity accounts for 20%-40% of total energy expenditure ◦ Factors influencing the EE of physical activity: Activity type, duration, intensity and frequency. ◦ The body mass of the individual ◦ His/her efficiency at performing the activity ◦ Any extraneous movements that may accompany the activity Thermoregulation ◦ Alterations in metabolism that occur as the body maintains its internal temperature (37°C /98.6°F) Assessing Energy Expenditure Energy expenditure can be assessed in four (4) ways: Direct Calorimetry ◦ Indirect Calorimetry ◦ Doubly-labelled Water ◦ Derived Formulas Assessing Energy Expenditure Direct calorimetry ◦ Measures dissipation of heat from the body Indirect calorimetry ◦ Measures consumption of O2 & expiration of CO2 ◦ The respiratory quotient & substrate oxidation ◦ RQ = 1.0 CHO being oxidized ◦ RQ =0.7 Fat ◦ RQ = 0.8 Protein Assessing energy expenditure Indirect Calorimetry Direct Calorimetry Assessing Energy Expenditure ◦The respiratory quotient & energy expenditure ◦ Exhaled air by subject analyzed ◦ Difference in composition of inhaled air and exhaled air reflects energy released from body Doubly labeled water ◦ Stable isotopes of water given as H218O & 2H2O ◦ Disappearance of H218O & 2H2O measured in blood & urine for ~3 weeks Assessing Energy Expenditure Derived formulas ◦ Harris-Benedict ◦ Men: BMR = 66.5 + (13.7 x W) + (5.0 x H) - (6.8 x A) ◦ Women: BMR = 655.1 + (9.56 x W) + (1.85 x H) - (4.7 x A) W= Weight in Kg; H= Height in cm; A= Age in years ◦ Mifflin-St. Jeor ◦ Men: REE = (10 x W) + (6.25 x H) - (5 x A) + 5 ◦ Women: REE = (10 x W) + 6.25 x H) - (5 x A) - 161 Activity Calculate the BMR and REE of a female who is 35 years old, weighs 125 lbs and is 5ft. 5 inches tall. Assessing Energy Expenditure Once resting/basal energy expenditure has been estimated using an appropriate prediction equation or measured, the value is then multiplied by the daily total energy expenditure ◦ A physical activity level (PAL) factor also called an activity factor (AF) is applied in order to average the daily total energy expended. ◦ These are intended to adjust daily energy intake needs relative to the individual’s activity level. Physical Activity Level/Activity Factor Activity Factor Level of Physical Activity Range 1.0-1.39 Sedentary, typical daily living activities (e.g., household tasks, walking to bus) 1.4-1.59 Low active, typical daily living activities plus 30 to 60 min of daily moderate activity (e.g., walking @ 5-7 km/hour) 1.6-1.89 Active, typical daily living activities plus 60 min of daily moderate activity 1.9-2.5 Very active, typical daily activities plus at least 60 min of daily moderate activity plus an additional 60 min of vigorous activity or 120 min of moderate activity. Energy Expenditure The energy expenditure of a sedentary adult female/male amounts to approximately 1800-2800 kcal/day. ◦ Physical activity by means of training or competition will increase the daily energy expenditure by 500 to >1000 kcal/h, depending on: ◦ physical fitness, duration, type and intensity of sport For example Endurance athlete: field research has documented hourly caloric expenditure in the range of 600 to 1200 kcal/hour. Estimated energy needs of such athletes are in the range of 50-80 kcal/kg/day. Biochemical Assessment of Physical Exertion Types of muscle ◦ Type I (“red”) – oxidative ◦ Has a large no. of mitochondria; capable of oxidizing glucose ◦ Beta-oxidation of fatty acids ◦ Used for aerobic endurance events ◦ Type IIa (“white”) - hybrid of I & IIb ◦ Type IIb (“white”) - fewer mitochondria & active glycolytic pathway ◦ Has fewer mitochondria ◦ Has a very active glycolytic pathway ◦ Used for short-duration anaerobic events and power events Biochemical Assessment of Physical Exertion Common measurements ◦ Respiratory quotient (RQ) ◦ The ratio of the volume of CO2 expired to the volume of O2 consumed ◦ Determines the relative participation of CHO and fats in exercise ◦ RQ for CHO 1.0 ◦ RQ for fat 0.70 ◦ RQ for protein 0.82 Biochemical Assessment of Physical Exertion COMMON MEASUREMENT Maximal oxygen consumption (VO2 max) ◦ The point at which an increase in the intensity of exercise no longer results in an increase in volume of oxygen uptake Energy System: ATP-CP (phosphagen) system ATP-CP energy system ◦ Quick source of ATP ◦ Cellular ATP and creatine phosphate ◦ Energy expended after approx. ◦ 10 to 25 seconds of strenuous exercise Energy System: The Lactic Acid System Lactic acid energy system ◦ Breakdown of glucose to lactic acid (lactate) ◦ Doesn’t require oxygen ◦ Rise in acidity triggers muscle fatigue Energy System: The Aerobic System The Aerobic system ◦ Breakdown of carbohydrate and fat for energy ◦ Requires oxygen ◦ Produces ATP more slowly Energy Systems Teamwork in energy production ◦ Anaerobic systems ◦ Aerobic systems Glycogen depletion ◦ Steady drop for first 1.5 hours ◦ Entirely depleted ~ 3 hours Fuel Sources during Exercise Major endogenous sources of energy during exercise: ◦ Muscle glycogen ◦ Plasma glucose ◦ Plasma fatty acids ◦ Intramuscular triacylglycerols Energy Sources Exercise intensity & duration ◦ Low intensity - plasma fatty acids ◦ Moderate intensity - increased fatty acid oxidation (due to muscle TG) ◦ High intensity - CHO oxidation & lactate production increase Level of exercise training ◦ Training increases muscle glycogen & TG stores Initial muscle glycogen levels Supplementation with carbohydrates through intestinal tract during exercise Exercise Intensity and Duration ◦Energy required for low-intensity exercise (25% to 30%) ◦ Muscle triacylglycerols, plasma fatty acid oxidation, small amount from plasma glucose ◦ Period of up to 2 hours ◦Increased exercise intensity (65% to 85% VO₂ max) ◦ Release of adipocyte fatty acids into plasma is reduced ◦ CHO oxidation ◦Moderate-intensity exercise (~ 65% VO₂ max) ◦ Total fat oxidation increases Level of Exercise Training Endurance training ◦ Increases an athlete’s ability to perform more aerobically ◦ Results in increase utilization of fat as an energy source ◦ Intramuscular triacylglycerol; plasma fatty acids ◦ CHO-sparing effect of enhanced fatty acid oxidation ◦ Because of slower depletion of muscle glycogen and plasma glucose Initial Muscle Glycogen Levels Ability to sustain prolonged moderate to heavy exercise depends on: ◦ the initial content of skeletal muscle glycogen High muscle glycogen levels allow exercise to continue longer Importance of initial muscle glycogen levels ◦ The inability of glucose and fatty acids to cross cell membrane rapidly to provide adequate substrate for mitochondrial respiration Carbohydrate Supplementation Muscle glycogen ◦ limiting factor for capacity to exercise at intensities requiring 70% to 85% VO₂ max Carbohydrate loading ◦ Maximizing glycogen content by dietary manipulation Modified regimen Fatigue during Exercise Muscle fatigue occurs when the supply of glucose is inadequate To delay muscle fatigue: ◦ the person must reduce workload intensity to a level that matches his/her ability to oxidize fat predominantly (as low as 30% VO2 max). Fatigue during Exercise High-intensity, short-duration exercise ◦ the production of lactic acid which lowers the pH of muscle cells ◦ accumulation of inorganic phosphate from the breakdown of creatine phosphate and ATP can interfere with the release of calcium ions from the sarcoplasmic reticulum ◦ muscle fibers fatigue rapidly if continuously stimulated but also recover rapidly after only a few seconds of rest. Fatigue during Exercise Low-intensity, long-duration exercise ◦ fatigue develops more slowly ◦ includes cyclical periods of contraction and relaxation. ◦ Recovery from fatigue after such repetitive activities can take from minutes to hours. ◦ After exercise of extreme duration e.g. running a marathon, it may take days or weeks before muscles achieve complete recovery ◦ likely due to a combination of fatigue and muscle damage. Potential strategies to delay the onset of muscle fatigue Carbohydrate loading Supplementation Adequate hydration Training techniques Recovery strategies Ergogenic aids References Gropper, Smith, and James Groff. Fifth Edition. Advanced Nutrition and Human Metabolism Widmaier, Raff, and Kevin Strang. Thirteenth Edition. Vander’s Human Physiology: The Mechanisms of Body Function Negro, M., S. Rucci, D. Buonocore, A. Focarelli, F.Marzatico. 2013. Sports Nutrition Science: an essential overview. Progress in Nutrition, (15) N. 1, 3-30 Burke and Greg Cox. The Complete Guide to Food for Sports Performance: Peak Nutrition for Your Sport Academy of Nutrition and Dietetics. 2016. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet. 116:501-528.