Exercise Physiology

Exercise Physiology By Danielle Logan, Michelle Haarmann, and Ben Stephens

Introduction • Exercise physiology is the study of the function of the body under the stress of acute and chronic physical activity • Exercise physiology is concerned with how the body responds to the intense demands placed on it by physical activity as well as the changes that occur in the body as individuals participate in exercise • Exercise physiologists are interested in studying all forms of physical activity including everyday life activities, sports activities, and exercise activities • Exercise physiology is all around us in the daily activities we engage in that require our bodies to make major physiologic adjustments such as: a slow walk, a fast run, physical labor 8 hrs each day, weight lifting, bodybuilding.

What is the role of an Exercise Physiologist? • To examine specific physiologic responses in an attempt to define adjustments made with acute exercise.

Acute Versus Chronic Adaptations • Refers to performing a short period of exercise. • Could take a few seconds, such as shot-put or running a 40-yd dash • Or could take a few hours such as running in an ultramarathon • Exercise physiology investigates how the body makes internal adjustments in the massive disruptions in homeostasis that occur with acute exercise. • Excersie physiologists also have much concern in the way that the body adapts to being chronically exposed to exercise stress • Chronic adaptations refers to a length of time over which changes take place in different physiologic systems during an exercise training program

The Use of Acute and Chronic Adaptations • Exercise physiologists apply the knowledge gained from the basic sciences to problems in exercise physiology, thereby gaining insights into how the body functions during exercise. • This information can be used as a basis for developing the best training practices in order to enhance athletic performance and health.

Activity Continuum • All exercises, athletic activities and general physical activities can all be placed on a continuum – This continuum is useful for classifying exercise in two ways: The metabolic and hemodynamic responses produced by a given activity. • The physical activity continuum ranges from activities that are anaerobic to some that are aerobic

Metabolic Response • Range from anaerobic to aerobic • Power speed and endurance tell us how intensely the activity is performed. • Shot-put takes only 2 to 3 seconds to perform and in that time frame, the athlete extends maximal effort with as much force as he or she can produce. • This example is a power event • Power is the application of a force relative to time. • If the force is applied in a short time frame, more power is generated such as in Olympic weightlifting, shot-put, and some running events such as the 40 yard dash or running up the stairs. • Speed events require a longer time period, resulting in a lower amount of power generated. • Speed events include 100 to 200 meter sprints, longer runs such as the 400 meter run, and weightlifting involving many repetitions

Specificity • One of the several basic training principles that must be paid attention to if a physical training program wants to produce optimal results. • Specificity principle: states that to maximize benefits, training should be carefully matched to an athlete’s specific performance needs or an individual’s goals.

Hemodynamic Response • The circulation of the blood • Exercises that promote a large amount of blood movement and moderate elevation in blood pressure involve endurance activities • These types of exercises are classified under the volume load heading because it is moving a large amount of blood through the circulation (aerobic exercise) • Load heading refers to the fact that the heart is stressed • Exercises that are anaerobic restrict blood movement and are the ones that lead to a sharp increase in blood pressure. In this case, the heart is said to be pressure loaded (such as in weightlifting)

Hemodynamic Response cont. • Exercises and activities can be classified and placed on a physical activity continuum • Most with fall throughout the continuum, but some can be placed at either extreme. • The physical activity continuum is very useful in helping coaches or personal fitness trainers deign the best exercise training programs for their athletes and clients. • For sports events that are in the middle of the metabolic continuum, a mixed training program is needed. • If an athlete is a power performer and practices cross training, he or she may be hurting more than improving.

Exercise Through Our Lives • Within exercise physiology, investigators are interested in studying exercise responses and adaptations across the life span. • They study all sorts of different people such as athletes, nonathletes, healthy people, unhealthy people, the elderly, and the young. • The investigators main goal is to find how exercise can be used to enhance the quality of life for everyone, especially for the elderly.

Focus on Science • The most rudimentary understanding of movement can be reduced to the study of the biomechanical processes that release bound or potential energy and convert it to free energy, which is involved at any moment in all biological processes, including muscular activity.

Energy • Energy is best understood as the ability to perform work (or exercise). • The concepts of work and energy are directly related. • As work increases, so does the transfer of energy.

Energy for Movement • Energy for movement comes from the food we eat (animal and plant sources), which provides energy-rich nutrients in the form of carbohydrates, fats, and proteins.

Carbohydrates & Fats • Two main energy nutrients • These energy nutrients are broken down by the body to their building block molecules and are processed by the liver for storage and use in the body. They are converted to another chemical to be used as energy for muscular activity.

Metabolism • Refers to all of the chemical reactions that take place in the body. • It is the sum of all catabolic and anabolic processes.

Catabolism • Is the process of breaking down the large energy nutrient molecules to their smaller constituent building blocks.

Anabolism • The process whereby smaller molecules are built up to larger molecules.

For movement to occur… • Catabolic (energy-releasing) processes are linked with anabolic (energy-trapping) processes for the purpose of producing another high-energy product that then becomes the direct donor of free energy for muscular activity called adenosine triphosphate (ATP). • ATP is an energy- rich compound that provides cells with a means of storing and conserving energy.

Anaerobic Production of ATP • The anaerobic production of ATP is an important means of powering movement and makes power and speed activities possible.

Phosphogen System • The phosphagen system is the metabolic pathway using creatine phosphate as the substrate that donates a phosphate group to ADP in the anaerobic formation of ATP. • It’s used primarily during very intense exercise lasting a few seconds. • The chemical process phosphorylation produces ATP.

Phosphagen System cont. • Metabolic power refers to how quickly the system can produce ATP, while metabolic capacity refers to the ability to make large quantities of ATP. • Creatine phosphate a compound found in muscles 3 times that of ATP as is responsible for why we can only sustain intense physical activity for a few seconds

Lactic Acid System • The breakdown of glucose (to produce ATP) is termed glycolysis. • During intense activity lasting longer than 10 seconds, exercising muscles rely more and more on glycolysis to pick up where the phosphagen system left off. • There is a limit to the ability of glycolysis to sustain ATP production in intense activity. This limitation is brought about by the end product of fast glycolysis: lactic acid.

Aerobic Production of ATP • When we engage in exercise at an intensity level that can be maintained continuously for long periods of time, ATP is produced in muscles through cellular respiration, a process that uses oxygen. • Mitochondria are the specialized cellular structures responsible for producing ATP during aerobic metabolism. • The breakdown of triglycerides is termed lipolysis. • The breakdown of fatty acids is termed beta-oxidation.

The Cardiorespiratory System • The pulmonary system delivers oxygen to the blood, whereas the cardiovascular system delivers blood to the working muscles. • In external respiration, oxygen diffuses from the air into the lungs and then into the blood circulating through the lungs. • Oxygen consumption = amount of blood delivered x amount of oxygen taken out of the blood by the working muscles.

Three things immediately happen in endurance exercise to meet the increased demand for oxygen… • 1.) The heart rate and the strength of cardiac contractions increase so that the cardiac output closely matches any level of oxygen consumption. • The is a massive redistribution of blood away from areas that do not participate in producing movement. • 2.) As exercise intensity increases, more oxygen is extracted from the blood as the blood passes through the capillaries of the working muscles. • 3.) The increase in oxygen consumption with exercise results from an increase in pulmonary ventilation. • Pulmonary ventilation is the bulk flow of air into and out of the lungs.

Thermoregulation • Humans and all other mammals are homeothermic, which means that we must maintain our own internal body temperatures. • This can become difficult when external conditions and temperatures become extreme. • During exercise, our bodies produce large amounts of heat. Only about 20 to 30% of expended energy is used to perform work, meaning the remainder is stored as heat.

Thermoregulation cont. • This excess energy must be removed to maintain our core temperature with in a reasonable limit. • A failure to adequately cool down can result in some type of heat illness, which could lead to serious medical issues or even death. • Thermoregulation becomes difficult to reach when humidity, heat, or both are at extreme levels. Performance declines in these conditions because our body’s circulatory system is responsible for dissipating this excess heat caused by exercise. This directly effects our ability to deliver oxygen to our muscles therefore decreasing aerobic performance.

Evaporation • Part of the reason performance declines in extremely hot and humid conditions is because blood is being taken away from the muscles in an effort to bring moisture to our skin to be evaporated. Evaporation of our sweat dissipates heat from our bodies. • It is difficult and often dangerous to exercise in extreme humidity because the body’s most efficient way of cooling itself becomes less effective and performance then declines. This is a result of the atmosphere being saturated with water. The sweat from our bodies evaporates at a far slower rate, incapacitating the cooling process. • This is why exercising in proper attire is important. If a person exercises wearing clothing made out of a material that hinders evaporation, then the body can’t cool itself as efficiently. Some exercise apparel is specifically designed to encourage the evaporation process.

Water Intake • It is extremely important to be properly hydrated while exercising, especially in extreme conditions. Studies have shown that maintaining proper hydration keeps core body temperatures relatively stable, and not being properly hydrated leads to an increased core temperature while exercising. Also physiological conditions are better when the exerciser is properly hydrated.

Muscle Fiber Types: A determinant of sports performance • There are many different types of muscles including skeletal, smooth and cardiac. There are also different types of fibers that make up these muscles. Important to sports performance, skeletal muscle fiber types have been seriously investigated since the 1970’s. • There is a strong link between performance and muscle fiber type. The three main muscle fibers are slow oxidative, fast oxidative glycoytic, and fast glycolytic fibers. These muscle fibers differ in size and peak tension. The larger oxidative fibers reach peak tension more slowly, and faster glycolytic fibers reach peak tension very quickly. • More explosive athletes (sprinters) have higher percentages of fast twitch fibers, and more endurance athletes (long-distance runners) have a higher percentage of slow twitch fibers.

Overtraining: Is More Really Better? • When do we draw the line between optimal training and overtraining? Many medical and physiological problems are associated with overtraining. There has been a substantial amount of research in this area aimed at understanding overtraining as it relates to physiologic, pathophysiologic, nutritional, immunologic, and psychological consequences. • Overtraining isn’t problem that can be remedied with a days rest. This is a chronic problem, and more research needs to be performed in order to identify strategies and guidelines to help avoid and overcome this problem. • http://www.youtube.com/watch?v=esrqV8IVorQ

Chapter Summary • Exercise physiology is the science of how the body functions during exercise and sports activity and how it changes during chronic exercise training • The activity continuum allows us to visualize acute exercise as power, speed or endurance events in terms of metabolic and hemodynamic responses • Energy is released from the energy nutrients during cellular mechanisms and captured in the form of ATP • The breakdown of ATP allows for muscular contraction • ATP is made in the muscles specifically depending on the type of activity a person is engaging in • ATP is made by primarily creatine phosphate and glucose breakdown during intense activity

Summary Continued… • For long-duration exercises, ATP is produced by cellular respiration • Thermoregulation is important for maintaining normal core temperatures when we exercise • Exercise in the heat and humidity results in increased cardiovascular stress and reduced exercise performance

Reference • Brown, S (2001). Introduction to exercise science. Philadelphia, Pennsylvania: Lippincott Williams & Wilkins.

Exercise Physiology