Sport and Exercise Medicine - Essay Example

Introduction: All sporting events require an athlete to adhere to certain training principles and guidelines. However, the training methods and requirements will vary. The training principles of a marathon runner will differ from that of a sprint runner. A knowledge of the body’s physiology and its application in the training regimen is thus very vital. In the past few decades, the disciplines of exercise science and exercise medicine have also evolved greatly to help sportspersons achieve their goal. SPORT AND EXERCISE MEDICINE “Sport and exercise medicine is a discipline, which draws upon basic and applied biomedical, and clinical science to ensure the prevention, diagnosis and management of sports and exercise related clinical problems. This discipline is relevant to the whole population and seeks to promote health, to prevent disease or injury, and to apply optimal treatment and measure outcomes.” (Henry A, 2005) Sports medicine is mainly concerned with the primary health care of the sporting population, which includes competitors, coaches, referees, etc. It addresses both the physical and mental health of those involved in sporting activity. Sports medicine also takes part in the selection procedure, planning and programming of the training process, and cares for epidemiological, hygienic, nutritional and other aspects of sport. At one time, sports medicine used to be dominated by the team doctor, who worked mostly with college, professional, and Olympic athletes. However, today, many disciplines including athletic training, biomechanics, exercise physiology and nutrition represent the sports medicine team. Nonprofessional athletes, children involved in sports or older adults training for foot races may also work with sports medicine specialists. (The American College of Sports Medicine n.d) SPORT AND EXERCISE SCIENCE “Sport and exercise science involves the study of the physiological, psychological, biomechanical and sociological influences on human performance in sport, work, and exercise.” (Department of Sport and Exercise Science, 2002) In sport, it can be considered as the study of movement and the associated functional responses and adaptations. The range of disciplines involved in exercise science is similar to those in sports medicine; however, it is “typically much broader than sports medicine, ranging from the study of how organ systems work at the cellular level when confronted with disease to improving the biomechanical efficiency.”(The American College of Sports Medicine n.d) In general, “a strict categorizing of a specific discipline (for example, exercise physiologist, dietitian, biomechanist) to either sports medicine or exercise science is difficult. It simply depends on the emphasis and application of the setting in which one works. What is important to understand is that many different disciplines comprise sports medicine and exercise science.”(The American College of Sports Medicine n.d.) “Without this multidisciplinary approach to the whole person, the end result may to be less than optimal. A rigorous training program, for example, may have little impact on the health or performance of an individual if nutritional considerations are neglected.”(The American College of Sports Medicine n.d.) In the practice of clinical sports medicine, exercise physiology plays an important role. Research in exercise physiology has shown how exercise affects the bodys systems, tissues, and cells. (Pate RR, Durstine JL, 2004). Current research is focussing on the role of exercise in subcellular, molecular, and chemical processes. The research findings will enable sports medicine physicians and other practitioners to help athletes to optimise performance, and nonathletes achieve better health through exercise. The application of exercise physiology theory and research, benefits many areas of sports medicine practice like exercise testing, safety, performance evaluation, correction of training problems, and prevention of problems that affect specific populations like older athletes, women, and children. There is an increasing demand for athletes at all levels to be better, faster, and stronger. For this, sports medicine practitioners and exercise physiologists need to work together in order to optimise sports and exercise performance, health, and safety. (Pate RR, Durstine JL, 2004) The normal muscle metabolic systems in exercise The body’s ability to produce energy is the key to improving performance in a sport like marathon. There are three key pathways of energy release in the muscles: 1. The adenosine triphosphate-phosphocreatine (ATP-PCr) energy pathway (phosphagen system) replaces ATP very rapidly. This would be useful in events requiring maximal short bursts of muscle power, such as the 100-meter dash. 2. The lactic acid energy pathway (anaerobic glycolysis), involves the rapid breakdown of muscle glycogen (glycolysis) under anaerobic conditions. ATP is replenished less rapidly but in greater quantities than the phosphagen system and is the predominant energy pathway in more prolonged events, like the 400 meters. Lactic acid accumulation in the blood causes muscle fatigue, which is a self-limitation for the further use of this energy pathway. 3. The aerobic system involves the aerobic metabolism of either carbohydrate (aerobic glycolysis) or fat (aerobic lipolysis), producing substantial quantities of ATP but at a slower rate than the other two pathways. This pathway predominates in more prolonged aerobic endurance events (Williams M, 2003.) ENDURANCE MARATHON RUNNING AND THE PHYSIOLOGICAL ASPECTS OF ADAPTATION AND TRAINING FOR THIS EVENT Metabolic Adaptations Metabolic adaptations, which occur in the body because of aerobic conditioning, helps in improved energy production. The mitochondria in the skeletal muscle becomes more efficient and develop an increased capacity to generate ATP by oxidative phosphorylation, which means that they can make more ATP to power muscle contractions. There is also an increase in the size and number of mitochondria and an increase in the level of aerobic energy producing enzyme systems. Studies have also shown that skeletal muscle myoglobin can increase by as much as 80%, and an increase in myoglobin can improve oxygen delivery to mitochondria. “Aerobic training also causes an increase in the muscles ability to mobilise and oxidize fat. This occurs by an increase in blood flow within the muscle and in the activity of fat-mobilising and fat-metabolising enzymes.” (Williams M, 2003). Since the muscle increases the ability to use fat as a fuel source, there is a shift in the energy substrate selection, wherein the trained muscle learns to rely more on fat as an energy source and less on carbohydrate. “This is important to endurance athletes because increased use of fat as an exercise fuel has a carbohydrate sparing effect” (Williams M, 2003), and this means improved performance. Cardiovascular Adaptations Cardiac hypertrophy and cardiac output: There is an enlargement of about 40% of the heart chambers, along with an enlargement of heart mass. The maximal cardiac output is also thus 40% greater. The resting cardiac output, however, is the same as that of a normal person. This is because of an increased stroke volume (about 50%) with a reduced heart rate. Thus, the heart-pumping effectiveness of each heartbeat is 40-50% greater than in a normal person but there is a corresponding decrease in heart rate at rest. (Guyton AC, 1986b.) Plasma volume and total haemoglobin content of the blood increases with endurance training, which improves oxygen delivery. The muscles become more efficient in extracting oxygen from the blood because of an increase in the capillary supply, myoglobin and mitochondrial content of the muscle fibres. The increase in the number of capillaries surrounding each muscle fibre allows greater exchange of gases, heat, wastes, and nutrients between the blood and working muscle fibres. This facilitates energy production, fat metabolism and muscular growth. (Williams M, 2003) Respiratory adaptations “Endurance exercise increases the ventilatory capacity of the lungs by increasing both breathing frequency and tidal volume. In submaximal exercise, the trained athlete ventilates less than before training.” (Williams M, 2003). There is an increase in the oxygen diffusing capacity because of greater perfusion through the pulmonary capillaries. (Guyton AC, 1986a.) VO2 Max: This is defined as the highest rate of oxygen consumption attainable during maximal exhaustive exercise. VO2 Max can be considered as the best indicator of cardiorespiratory endurance capacity. There is an average increase of 20% VO2 Max following six months of aerobic conditioning. This is brought about by a combination of two factors. An increase in cardiac output and an increase in the arteriovenous oxygen gradient (Williams M, 2003.) Lactate Threshold Anaerobic metabolism of glucose produces lactic acid, which is an end product. Lactic acid build-up inside muscle cells causes fatigue. As the intensity of exercise increases, more lactic acid is produced and begins to appear in the blood as a waste product. The lactate threshold is the point where blood lactate begins to appear. This is also a measure of cardiorespiratory fitness. “Endurance training increases the lactate threshold, which means a higher level of energy production can occur by the aerobic pathway before the anaerobic pathway is called into play.” (Williams M, 2003.) Principle of Progressive Increasing of Load in Training: The rate at which an athlete improves performance depends directly on the rate and manner in which the load is increased during training. This load in training has to be increased gradually, according to an individual’s abilities. The body reacts physiologically and psychologically to the demand of the increased training load. This principle is the basis for all planning of athletic training and should be followed regardless of the level of performance of an athlete. Exercise is a form of stress, and the body adapts to this stress by getting stronger. According to the overload principle, an exercise stimulus must be of some threshold intensity to bring about a training adaptation. “To force the body to continue to adapt, the stimulus must continually become more intense. This is known as progressive overload.” (Bulletin No. 51, 2000). An increase in the training intensity can be achieved by increasing the load, the workout frequency, the workout duration, or the power output. Consequences of progressive load As the load is increased, muscle size and strength increases. Increasing the workout duration increases endurance. Finally, as power output during the workout is increased, speed increases. Specificity Principle The Specificity Principle states that the metabolic adaptations that occur in response to a training stimulus are specific to the type of overload applied. If the resistance training is intense enough, muscle size and strength increases, while an increase in cardiovascular endurance is achieved by aerobic exercise. A specific exercise can cause specific adaptations in the body, which in turn creates specific training effects (Bulletin No. 51, 2000.) Lactate threshold training In training for endurance events like marathon, increasing the lactate threshold “enables an athlete to race more effectively at intensities significantly below lactate threshold, near lactate threshold, and above lactate threshold.” (Mierke K, 2005) “Training continuously at about 85 to 90% of the maximum heart rate for 20 to 25 minutes will improve the lactate threshold. A session should be conducted once a week and commence eight weeks before a major competition. This will help the muscle cells retain their alkaline buffering ability.”( Sports Coach, 1997a) The VO2max will also improve as a result. Interval Training “Interval training sessions include precisely measured intervals that match the athletes sport, event and current level of conditioning.” (Quinn E, 2005). After an anaerobic threshold testing (AT), which measures the blood-lactate of an athlete during intense exercise is performed; the results are used to determine the appropriate intensity and duration of the intervals. Interval training works both the aerobic and the anaerobic system. This repetitive form of training leads to an adaptation response. The body builds new capillaries, and there is better delivery of oxygen to the working muscles. A higher tolerance to the build-up of lactate is developed in the muscles, and the heart muscle is strengthened. These changes result in improved performance, especially of the cardiovascular system. Interval training also helps prevent injuries associated with repetitive endurance exercise, and the training intensity can be increased without over training or burn-out. (Quinn E, 2005.) Heart rate training zones: These are calculated by taking into consideration the maximum heart rate (MHR) and resting heart rate (RHR). (Sports Coach, 1997b.) a. The energy efficient or recovery zone (60% to 70%)Basic endurance and aerobic capacity increase by training within this zone. Recovery running should be completed at a maximum of 70%. Another advantage to running in this zone is that fat is utilized to generate energy and muscles are able to re-energise with glycogen. b. The aerobic zone (70% to 80%) Training in this zone develops the cardiovascular system. There is an improvement in the bodys ability to transport oxygen and carbon dioxide in the muscles. c. The anaerobic zone (80% to 90%) Training in this zone develops the lactic acid system. In this zone the individual anaerobic threshold is found (also known as point of deflection-POD). At these heart rates, the main source of energy is the glycogen stored in the muscle, instead of fat. “One of the by-products of burning this glycogen is lactic acid. Through correct training, it is possible to delay the POD by being able to increase the body’s ability to deal with lactic acid for a longer period of time or by pushing the POD higher.” (Sports Coach, 1997b) d. The red line zone (90% to 100%) “Training in this zone will only be possible for short periods of time. It effectively trains the fast twitch muscle fibres and helps to develop speed. This zone is reserved for interval running and only the very fit are able to train effectively within this zone.” (Sports Coach, 1997b) Conclusion: It is therefore clear that training for an endurance event like the marathon requires proper training methods and a knowledge of the normal body physiology, especially with respect to exercise recovery. Application of these principles in training not only optimises the performance and endurance of the individual but also helps in aiding recovery and reducing the risk of injury. ****************************************************************************** REFERENCES Bulletin No. 51(2000). Endurance Performance. [Online]. [Accessed 1st November, 2005] Department of Sport and Exercise Science, 2002 [Online]. [Accessed 3rd November, 2005] Guyton AC (1986a). Respiration in exercise. Textbook of medical physiology, 7th edition. p.1014. Guyton, AC (1986b). The cardiovascular system in exercise. Textbook of medical physiology, 7th edition. pp.1016-1017. Henry A (2005) [Online]. [Accessed 1st November, 2005] http://www.nuigalway.ie/physiology/Downlodable/sports_med.pdf Mierke K (2005) Lactate Threshold Training. [Online]. [Accessed 2nd November, 2005] Pate RR, Durstine JL (2004) Exercise physiology and its role in clinical sports medicine. South Med J. 97(9):881-5. Quinn E (2005) Interval Training. [Online]. [Accessed 3rd November, 2005] http://sportsmedicine.about.com/cs/conditioning/a/aa030802a.htm Sports Coach (1997a). Improving your Lactate Threshold. [Online]. [Accessed 2nd November, 2005] Sports Coach (1997b). Heart rate training zones. [Online]. [Accessed 2nd November, 2005] http://www.brianmac.demon.co.uk/hrm1.htm The American College of Sports Medicine.(nd) What is Sports Medicine and Exercise Science? . [Online]. [Accessed 3rd November, 2005] http://acsm.org/pdf/Careers092501.pdf Williams M (2003). Sport Science Research: Can It Improve Your Marathon Time? [Online]. [Accessed 2nd November, 2005] Read More