Biochemistry of sport Professor Dr. Najat A. Hasan (MB ChB, MSc, PhD in Clinical Biochemistry, College of Medicine -Alnahrain University, Baghdad. Iraq) Learning Objectives: • To develop an awareness of the basic chemical process that the body uses to produce energy in the muscles • To develop an understanding of the body’s three main energy systems • To introduce the effect of training and exercise on the energy systems -SPORT is a Physical activity where skeletal muscles contraction result in an increase in energy expenditure. Principles of Training or Sports • Overload – occurs when a system is exercised at a level beyond which it is normally accustomed • Specificity – Training is specific to the muscle fibers involved – Type of exercise • Reversibility – Gains are lost when overload is removed Different Methods of sports training • There are many types of sports training methods practiced through-out the world. Three of the main types: – Weight Training: Increases strength . focus on totally different parts of the body: Chest, shoulders, back, arms, legs and even neck . – Speed Training: Speed training is influenced by : - Strength -Endurance -Technique – Flexibility training: All pro athletes start and finish training sessions by doing flexibility exercises. – Not only helps out in performance, but it also helps lower back pain. - Stretching increases tissue temperature, blood supply, nutrient transport to tissue and synovial fluid. The energy sources of physical activity is dependent on: 1. Intensity of the physical activity 2. The duration of physical activity 3. Personal characteristics The combination of characteristics of physical activity (intensity , duration) ,genetic features, fitness will determine the ratio between various energy production pathways utilized by the muscles Energy systems 1. the high energy phosphate system (ATP-CP System) 2. the anaerobic glycolytic system (Lactic Acid System) 3. the aerobic oxidative system (Oxygen System) 1. The High Energy Phosphate System Overview Primary energy source: ATP( 2-3 s) , Stored ATP, CP Duration of activity: 7-12 s Sporting events: Weight lifting, high jump, long jump, 100m run, 25m swim Advantages: Produce very large amount of energy in a short amount of time Limiting factors: Initial concentration of high energy phosphates (ATP, PC) - The usefulness isn’t the AMOUNT of Energy but the QUICK & POWERFUL movements - For longer periods of work = The Aerobic & Anaerobic Energy System must be utilized Training: the High Energy Phosphate System a) Interval training: - 20% increase in creatine phosphate(CP ) stores - no change in ATP stores - increase in ATPase function (ATP -> ADP+P) - increase in creatine phosphokinase (CPK) function .CPK breaks down CP molecule and allows ATP resynthesis b) Sprint training: - increase in CP stores up to 40% - 100% increase in resting ATP stores 2. The Anaerobic Glycolytic System Overview Primary energy source: Stored glycogen, blood glucose Duration of activity: 12 s – 3 min Sporting events: 800m run, 200m swim, downhill ski racing, 1500 speed skating Advantages: Ability to produce energy under conditions of inadequate oxygen Limiting factors: Lactic acid build up, H+ ions build up (decrease of pH) • Starts when: – the reserves of high energy phosphate compounds fall to a low level – the rate of glycolysis is high and there is a buildup of pyruvic acid Hydrolysis of Glucose: 2 molecules of ATP + 2 molecules of pyruvic acid Hydrolysis of Glycogen : 3 molecules of ATP + 2 molecules of Lactic acid The highly complex metabolic pathways of glycolysis ) Anaerobic Threshold: The exercise intensity at which lactic acid begins to accumulate within the blood. The point during exercise where the person begins to feel discomfort and burning sensations in their muscles. Lactic acid is used to store pyruvate and hydrogen ions until they can be processed by the aerobic system Effect of Training on the Anaerobic Glycolytic System Rate of lactic acid accumulation is increased in the trained individual. This rate can be decreased by: a) reducing the rate of lactate production - increase in the effectiveness of the aerobic oxidative system b) increasing the rate of lactate elimination - increased rate of lactic acid diffusion from active muscles - increased muscle blood flow - increased ability to metabolize lactate in the heart, liver and in non-working muscle …cori cycle 3. The Aerobic Oxidative System Overview Primary energy source: Glycogen, glucose, fats, proteins Duration of activity: > 3 min Sporting events: Walking, jogging, swimming, walking up stairs Advantages: Large output of energy over a long period of time, removal of lactic acid Limiting factors: Lung function, max.blood flow, oxygen availability, excess energy demands Primary source of energy (70-95%) for exercise lasting longer than 10 minutes provided that: a) working muscles have sufficient mitochondria to meet energy requirements b) sufficient oxygen is supplied to the mitochondria c) enzymes or intermediate products do not limit the Kreb’s cycle The Oxidative Phosphorylation System • Two Pathways: Krebs Cycle & Electron Transport Chain • There is resynthesis of ATP by combining ADP and P in the presence of oxygen • Takes place in mitochondrion (contains enzymes, co-enzymes) • Energy yield from 1 molecule of glucose is 36 ATP molecules • Energy yield from 1 molecule of fat up to 129 ATP molecules • By-products of this reaction: carbon dioxide, water O2 enters the system, stopping the breakdown of glycogen to lactic acid , glycogen breaks down into: ATP + CO2 + H20 These byproducts are easier to get rid of :CO2 is expelled by the lungs H2O is used in the muscle The Substrates for the Aerobic System Carbohydrates& fat With prolonged exercise, Carbohydrates are the first fuel choice, as exercise continues, Fat becomes predominant Proteins Protein is not a main fuel source except in an emergency direct muscle oxidation (branched chain amino acids) gluconeogenesis in liver from amino acids Proteins provide low rate of ATP-energy production Limited total energy capacity Is considered significant source of energy during long endurance events Factors Affecting Physical Performance Somatic Factors Nature of the Work Psychic Factors Environmental Factors Sex Intensity Attitude Diet Age Duration Motivation Temperature Body distribution Technique (efficiency) Air pressure (hypobaric and hyperbaric) State of health Body position Air pollution Drugs Mode Noise Strength Type Fibre type distibution Work:rest schedule Muscle Fiber Types: A determinant of sport performance Muscle fibers have been identified as red or white fibers, where red fibers were suited to long-term slow muscle contractions .White fibers were suited to high-speed contractions. The three major muscle fiber types seen in human skeletal muscle:Slow oxidative fiber (I, aerobic), called slow-twitch oxidative Fast glycolytic fibers(II a, mixed) Fast oxidative glycolytic(II b, anaerobic) The metabolic and contractile properties of these fibers can influence exercise performance. Slow-twitch fibers are fatigue-resistant and thus suited to longerterm, aerobic activities. They have greater myoglobin and mitochondria levels than fast twitch fibers, and are thus reliant upon aerobic metabolism to function. They contract at a much slower speed than fast-twitch fibers and have a low glycolytic capacity. The major differences between the fiber types are displayed in Table 1. Effect of Training on Aerobic Systems • Endurance training is the most effective method (long duration several times per week): - increases vascularization within muscles - increases number and size of mitochondria within the muscle fibers - increases the activity of enzymes (Krebs cycle) - preferential use of fats over glycogen during exercise • Endurance training increases the max aerobic power of a sedentary individual by 15-25% regardless of age • An older individual adapts more slowly The Power Of The Aerobic System • Evaluated by measuring the maximal volume of oxygen that can be consumed per kilogram of mass in a given amount of time • This measure is called aerobic power or VO2 max (ml/min/kg) • Factors that contribute to a high aerobic power: a) arterial oxygen content (CaO2) depends on adequate ventilation and the O2-carrying capacity of blood b) cardiac output (Q = HR x stroke volume) increased by elevation of the work of heart and increased peripheral blood flow c) tissue oxygen extraction (a-vO2 diffusion) - depends upon the rate of O2 diffusion from capillaries and the rate of O2 utilization •When the muscle does not get enough oxygen, exhaustion is reached causing immediate and involuntary reduction in intensity VO2max is Product of maximal cardiac output (Q) and arteriovenous difference (a-vO2) : VO2max = HRmax x SVmax x (a-vO2)max, SV is the stroke volume. Factors Increasing Stroke Volume (SV ) Increased SVmax Preload (End Diastolic volume) • Plasma volume • Venous return • Ventricular volume Afterload (Total peripheral resistance) • Arterial constriction • Maximal muscle blood flow with no change in mean arterial pressure Contractility a-vO2 Difference and Increased VO2max Improved ability of the muscle to extract oxygen from the blood Muscle blood flow Capillary density Mitochondrial number Increased a-vO2 difference accounts for 50% of increased VO2max arterio-venous difference in O2 (a-vO2) Structural and Biochemical Adaptations to Endurance Training Mitochondrial number Oxidative enzymes: Krebs cycle (citrate synthase,CS) Fatty acid (-oxidation) cycle Electron transport chain NADH shuttling system Change in type of LDH Adaptations quickly lost with detraining Detraining Changes in Mitochondria About 50% of the increase in mitochondrial content was lost after one week of detraining All of the adaptations were lost after five weeks of detraining It took four weeks of retraining to regain the adaptations lost in the first week of detraining Effect Intensity and Duration on Mitochondrial Enzymes Citrate synthase (CS) Marker of mitochondrial oxidative capacity Light to moderate exercise training • Increased CS in high oxidative fibers (Type I and IIa) Strenuous exercise training • Increased CS in low oxidative fibers (Type IIb) Biochemical Changes and FFA Oxidation Increased mitochondrial number and capillary density Increased capacity to transport FFA from plasma to cytoplasm to mitochondria Increased enzymes of oxidation Increased rate of acetyl CoA formation Increased FFA oxidation Spares muscle glycogen and blood glucose FFA Oxidation and Glucose-Sparing Mitochondrial and Biochemical Adaptations and Blood pH Blood Lactate Concentration Balance between lactate production and removal Lactate production during exercise depend on: NADH, pyruvate, and LDH in the cytoplasm Blood pH affected by blood lactate concentration pyruvate + NADH LDH lactate + NAD Benefits of running/jogging/exercise 1. 2. 3. 4. 5. 6. 7. 8. Reduction in premature deaths Lowers risk of developing high BP Reduces risk of developing colon & breast cancer Reduces risk of developing diabetes Reduces or maintains body weight/fat Builds and maintains healthy muscles bones and tissue perfusion. Enhance physical, sport performance Improves psychological well-being, reduces depression, anxiety, HYDRATION Sweat losses vary between athletes but increase with temperature, intensity & duration of exercise …(3.7 L/hr) Physiological responses to dehydration: 1%: thirst 2%: decreased sweat rate, cardiac output, VO2, muscle strength and liver glycogen, therefore, decreased performance 5%: discomfort, alternating states of lethargy and nervousness, irritability, fatigue, loss of appetite 7%: Extreme danger; salivating & swallowing becomes difficult Before Exercise: Pre-cooling improves endurance performance (cool shower/bath/vests). 500mL every 2 – 3hrs prior to exercise (water, juice, milk, cordial, sports drink) and 5ml/kg immediately before exercise During: 250mL every 15-20min OR as much is comfortable during exercise (water, sports drink) After: 150% of fluid deficit; Aim for 500mL to 1000mL (sports drinks, as the electrolytes help stimulate the thirst drive)
