Coursework 2 Name: Mohamed Abdulwahab Exercise metabolism Title: In the light of the energy systems used during prolonged endurance events, critically analyse the nutritional strategies that a marathon runner should adopt before and whilst running a marathon in temperate environmental conditions (16-18oC). 1. Introduction: 1. 1 Energy intake: 1. 2 Fluid intake: 1. 3 Carbohydrate intake: 2. Building energy and fluid: 1. Before competition: 2. During competition: 3. Nutritional recommendation: 3. 0 Summary: 4. 0 Reference: 1. 0 Introduction:
The term energy system refers to the body’s ability, or power, to do physical work. The energy system requires to do body work that takes several different forms: mechanical, electrical, light, radiant, and heat (Economos, 1993). Energy system is like matter, which can neither be created nor destroyed (Bortz, 1993). It can only be changed into another form; therefore energy is constant cycle in the body and environment (Nelson, 1993). Potential energy is stored energy which is ready to be used. Kinetics energy is active energy which can be used to do work (Burke, 1991). Energy balance n a physical activity requires a base of sound nutrition to supply the substrate fuels, which along with oxygen (O2) and water (H2O) meet widely varying levels of energy demand for body action (Gollan, 1991). Fuel sources are the basic energy nutrition in the diet, primarily carbohydrate and some fat (Read, 1991). Their metabolic products-glucose, glycogen, and fatty acids-provide ready fuel sourced for the chemical energy reactions within cells (Murray, 1998). The main energy compound of the body cells is needed during a marathon run is aerobic system (Horswill, 1998).
It has rightly a form of energy currency of the cell. A long-term energy system, when exercising more than 2 minutes is required O2 dependant, or aerobic energy system (Pate, 1992). A constant supply of O2 in the blood is necessary for continued exercise (Branch, 1992). Especially cells organelles, the mitochondria are located within each cell, produce large amounts of adenosine triphosphate (ATP) (Hargreaves, 1996). The ATP is produced mainly from glucose and fatty acids and supplies the continued energy needs of the body (Dillo, 1996).
When the fuel nutrition becomes depleted during exercise, as an energy demands increase the body burns blood glucose and muscle glycogen as well as reserves from fatty acids to provide energy (Angus, 1996). With prolonged exercise levels of these nutrition fail too low to sustain the body continued demands, fatigue followed and exhaustion threatens (Fabbriao, 1996). A marathon runner, energy system is defined as aerobic capacity, which depends on the body’s ability to deliver and the use of O2 in sufficient quantities to meet the demands of increased level of exercise (Coyle, 1986).
O2 uptake increases with exercise intensity until either the demand is net or the ability to supply it is exceeded (Hammert, 1986). The maximum rate that the body can take in O2, or aerobic capacity is called the Vo2max the maximum uptake volume of O2 (Ivy, 1986). This capacity determines the intensity and duration of exercise that an athlete can perform (Coyle, 1986). A long-distance race requires the sustained production of high rates of energy production, with the typical contribution of aerobic energy system varying according to the duration of the race (Costill, 1985).
Aerobic metabolism accounts for the greater majority of the energy cost of long-distance events, especially half-marathon and marathon races (William, 1996). The elite level of long-distance running, particularly in males, is dominated by African runners, are outstanding competitor in half-marathon and marathon events (Wilson, 1996). 1. 1 Energy intake: Endurance athletes are involved in events where there is continuous movement for longer than 30 minutes (Burrin, 1996).
Some endurance sports combine periods of slow, continuous movement with periods of fast, quick burst of movement, and other endurance sports require continuous movement overlong-distances or time periods (Tsintzas, 1995). In the types of activity there is a premium on supplying sufficient energy and fluid to assure that the athlete does not become exhausted or over-heated from the continuous energy burn (Williams, 1995). A failure to supply sufficient energy of the right type will lead to early fatigue and poor athletic performance (Williams, 1995).
The goal for the endurance athlete is therefore to establish a workable strategy for supplying sufficient energy and fluids (Williams, 1995). Before and during practice and competition to sustain muscular work for a long-duration and at the highest possible intensity (Wilson, 1995). Aerobic metabolism is the energy system of greatest importance for endurance athletes. In this energy pathway oxygen is used to help transfer phosphorus into new ATP molecules (Burrin, 1995). Aerobic metabolism occurs in the mitochondria of the cells, where the vast majority of all ATP is produced from the entering acetyl-CoA, (Burrin, 1995).
Fast can be converted to acetyl-CoA through a process called beta-oxidative metabolism pathway (Burrin, 1995). This pathway is very oxygen dependant which means that fast can only be burned aerobically (Wilson, 1995). The ability of an athlete to achieve a steady state of oxygen uptake into the cells is a function of how well an athlete is aerobically conditioned (Coggan, 1992). An athlete that frequently trains aerobically is likely to reach a steady state faster than one does not train aerobically (Coggan, 1992).
In theory once an athlete reaches a level of oxygen uptake that matches oxygen requirement for the given level of exertion (Coggan, 1992). The exercise could go on for as long as the body’s carbohydrate level and fluid did not reach a critical state (Sherman, 1996). For instance a long-distance runner is in a steady state could continue running provided the runner replaced the carbohydrate and fluid that are used in the activity (Sherman, 1995). Therefore, endurance is enhanced with a periodic intake of carbohydrates and fluid during the activity (Swanson, 1992).
Athletes with different levels of conditioning are likely to achieve steady state at different levels of exercise intensity (Sherman, 1995). When athletes are being well-conditioned they might be able to maintain a steady state at a high enough level of exercise intensity to easily win a race (Williams, 1995. In other words, they can go really at a fast paced but still provide enough oxygen to your cell to satisfy your aerobic needs (Swanson, 1992). 1. 2 Fluid: As athletes exercise there is an inevitable loss of body water through sweat (Economos, 1993).
The cooling system plus the normal urinary water loss may amount cover 10 litres of daily water loss when exercising in a warm environment (Borts, 1993). In a hot or humid environment water losses may exceed three litres per hour, but may be less than 0. 5 litres per hour cool dry environment (Nelson, 1993). Despite the high rates of sweat losses experienced by athletes, most athletes replace on fifty percent of the water that is lost, a behaviour that inevitably leads to progressive dehydration and a decline in performance (Nelson, 1993).
Researches have clearly demonstrated that even a slight dehydration of two percent of body weight causes a measureable decrease in athletic performance (Borts, 1993). Therefore, when athletes take steps to satisfy fluid requirements, they are helping to guarantee optimal athletic performance (Economos, 1993). 1. 3 Carbohydrate: Athletes require carbohydrate during both low and high intensity activities (Burke, 1991). When carbohydrate stores are depleted the athlete quickly becomes fatigued and performance drops dramatically (Gollan, 1991).
However, since the storage level of carbohydrate is relatively low gen compared fat stores; athletes must make a conscious effort to replace carbohydrate at every opportunity (Read, 1991). When having high levels of stored carbohydrate (glycogen) and consuming carbohydrates during exercise that last up to an hour or more are well-established techniques for optimizing athletic endurance (Murray, 1998). Consuming carbohydrate during exercise helps to maintain blood sugar (glucose) and insulin, which encourages sugar uptake by working muscles (Horswill, 1998).
This helps to increase the muscular metabolism of carbohydrates and also helps to assure that carbohydrates are not depleted during exercise (Horswill, 1998). The concentration of carbohydrate consumed early during endurance running may influence the degree to which the athlete gets gastrointestinal (GI), discomfort (Murray, 1998). It was found that a 5. 5 percent (13 gram of carbohydrate per 8 ounces of fluid), carbohydrate solution produced the same level (relative low) of GI distress as plain water (Pate, 1992). A 6. percent (18 gram of carbohydrate per 8 ounces of fluid), solution, on the other hand, doubled the incident of distress when athletes were asked to perform the same exercise (Branch, 1992). In addition, only the 5. 5 percent carbohydrate solution imparted a significant improvement in performance (Branch, 1992). In a study of marathon running performance, that are running over 26 miles, were asked to consume either water, a 5. 5 percent carbohydrate solution or a 6. 9 percent carbohydrate solution on three occasions (Pate, 1992).
The fastest times were recorded when they consumed the 5. 5percent carbohydrate solution, while consuming the 6. 9 percent solution resulted in times that were similar to consuming plain water (Hargreaves, 1996). Although, athletes have a tremendous need for carbohydrate, trying to provide too much too fast causes difficulties and may detract from performance (Dillo, 1996). Therefore, it appears clear that having a carbohydrate containing beverages during exercise is a very good thing to do (Angus, 1996).
Resynthesis of glycogen following activity is also important, since glycogen reserves are severely depleted following activity lasting an hour or longer (Fabbrioa, 1996). The efficiency of glycogen resynthesis is dependent on several factors, including: (1) the timing of carbohydrate intake, (2) the amount of carbohydrate consumed, (3) the type of carbohydrate consumed, and (4), the degree to which muscles has been damaged during the exercise (Fabbrioa, 1996). 2. 0 Building energy and fluid: The importance of building and maintaining energy reserves to support endurance exercise is well-established (Angus, 1996).
It is very clear that endurance athlete who begins competing with more stored carbohydrates have more available at the end of the competition (Coyle, 1996). This difference alone may be enough to determine the winner. In addition, athletes who are better hydrates during competition perform better than those who are less well-hydrated (Coyle, 1996). Having optimal carbohydrates and fluid intake does not happen automatically. It is something that must occur with foresight and planning (Angus, 1996). 2. 1 Before competition: When consuming carbohydrates prior to exercise, there is improved performance.
The general recommendation is for athletes to consume between 800 to 1200 calories during the hours that precede competition (Costill, 1985). Foods consumed prior to competition should be foods that have been consumed without difficult prior to training (Costill, 1985). Trying to improve carbohydrate status before a competition by trying out new foods, like gels or sports drinks is an almost guaranteed formula for competitive disaster (Costill, 1985). Consumption of fluids prior to competition is also important and since glycogen storage requires additional fluids carbohydrate consumption should lways take place with substantial fluid intake (William, 1996). Since it is common for athletes to drink only when thirsty a conscious effort should be make to consume fluids even when not thirsty (William, 1996). Getting and staying well-hydrated may be the single most important thing athlete can do to assure good athletic performance (Wilson, 1996). Since it is almost impossible to adequately replace all fluids lost during training or competition it is useful for athletes to enter the exercise in a well-hydrated state (Burrin, 1996).
It is impossible to become well-hydrated during exercise if athlete enters the exercise poorly hydrated to begin with (Burrin, 1996). Assuming that ample fluids have been consumed during the day leading up to the re-competition or practice athletes should consume an additional 10 to 13 gram of fluid approximately two hours before the exercise begins (Wilson, 1996). After this fluids should be consumed every 15 to 30 minutes to maintain prior to exercise (William, 1996). The athlete will know if you’ve adequately hydrated yourself by checking on the colour of the athlete urine (Tsintzas, 1995).
Dark urine suggests that athlete is not well-hydrated, while clear urine suggests that athlete is well-hydrated (Stanzas, 1995). Using sports beverages (lucazad) prior to exercise is useful because they provide the two things athletes need the most: carbohydrates and fluids (William, 1995). Since carbohydrate is typically the limiting energy substance (that will run out before fat or protein runs out) in exercise (William, 1995). When starting exercise with more of it is in the tissues should aid exercise endurance (William, 1995).
In low-intensity but long-duration exercise, fat may be the primarily fuel, but fat requires carbohydrates to burn completely (Singh, 1995). In either case, when carbohydrates (glycogen stores and blood glucose) are depleted, exercise performance is dramatically reduced (Wilson, 1995). This basis behind carbohydrate loading is to put as much carbohydrate in the tissue as they can hold (Wilson, 1995). 2. During competition: A marathon race where fluid are available at regular intervals, the athlete should take full advantage of each fluid station and consume fluid (Burrin, 1995).
Since water is constantly being lost, frequent and regular consumption of fluid helps to maintain the body water level (Burrin, 1995). To understand how much fluid an athlete needs to consume during practice or competition, a log should be maintained with the amount of fluid consumed and the beginning and ending weight of the athletes (Sherman, 1995). If an athlete consumes 26 gram during practice and weighs 26 gram less at the end of practice than at the beginning this athletes should learn to consume an additional 26 gram of fluid during practice or competition (Sherman, 1995).
Consumption of fluids that contain carbohydrates is important during exercise or competition and properly designed sport beverages can benefit in providing both fluid and carbohydrates quickly (Coggan, 1992). Carbohydrate solution of between 5 and 6 percent delivers both the carbohydrate and the fluid quickly (Swanson, 1992). A higher carbohydrate concentration slows delivery to the muscles by delaying gastric emptying and may increase the risk of gut upset (Swanson, 1992). A small amount of sodium helps drive the desire to drink and in so doing helps to assure that the athlete stays better hydrated (Coggan, 1992).
Sodium may also benefit in getting the water and carbohydrate absorbed more quickly as well as helps to maintain blood volume (Economos, 1993). Maintaining of blood volume is an important predictor of athletic performance (Economos, 1993). There is some evidence that hyponatremia (low level of blood sodium), which results from large losses of sodium in sweat that goes unreplaced, occurs endurance and ultra-endurance events (Borts, 1993). This is a rare but a serious condition that may result in comas, or death (Nelson, 1993). The beverage should be taste good to the athlete.
The taste sensation may be altered during exercise so there is no guarantee that a fluid, athlete enjoys drinking while exercising. Make sure that an athlete tries different flavours during exercise to determine what is best liked. The carbohydrate should be from a combination of glucose and sucrose. Beverages containing predominantly fructose increase the risk of creating gut upset. 2. 3 Nutritional recommendation: There are several rules of nutrition that apply here. Among them is the idea of the need to consume a wide range of variety of foods to assure that the body is exposed to all of the essential nutrients (Burke, 1991).
On the backside of this rule, there is another benefit. By consuming a wide range of variety of foods, athletes can avoid being exposed to any potentially toxic substances that are more prevalent in some foods (Gollan, 1991). Therefore, eating a wide range of variety of foods is a good nutritional rule to live by (Read, 1991). Another rule is the idea that it is possible to eat too much of something, even if athletes think it’s good for them (Read, 1991). Learning to balance the diet through variety will help ensure the body of both proper maintenance and adequate nutrient intake (Gollan, 1991). 3. Summary: In general, athletes with long training schedules should focus on the consumption of diets that are high in carbohydrate and should develop a drinking habit that frequently delivers fluids to the body. While fats, constitute a major proportion of burned energy for endurance (aerobic) activities the storage capacity for fat is relatively high for even the leanest athletes. The storage capacity for carbohydrate, however, is limited. Since fats require some carbohydrate to be completely burned, the limited storage capacity for carbohydrate cam limit the body ability to burn fat during exercise.
To overcome this limitation athlete should be constantly vigilant to keep body stored of carbohydrate at maximal levels before activity begins and should replace carbohydrate during activity throughout whatever means are available. A failure to supply suffienct carbohydrate before and during endurance activity will significantly reduce athletic performance. 4. 0 Reference: • Economos, D. , Borts, Z. , and Nelson, R. 1993. Nutritional practices of elite athletes. Sports. Med. 16:383. • Burke, L. , Gollan, R. , and Read, R. 1991. Dietary intake and food use of groups of elite Australian male athletes. Int. J. Sports Nutr. 1:378. • Murray, R. and Horswill, A. , 1998. Nutrition requirements for competitive sports. In nutrition in exercise and sport, 3ed. 521-558. • Pate, R. , and Branch, D. 1992. Training for endurance sport. Med. Sci. Sports Exer. 24:S340. • Hargreaves, M. , Dillo, P. , Angus, D. , and Fabbraio, M. 1996. Effect of fluid ingestion on muscle metabolism during pro-longed exercise. J. Appl. Physiol. 80:363-6. • Coyle, E. , Coggan, A. , Hammert, M. , and Ivy, L. 1986. Muscle glycogen utilization during pro-longed strenuous exercise when fed carbohydrate. J. Appl. Physiol. 61:165-172. • Costill, D. 1985. Carbohydrate nutrition before, during, and after exercise.
Fed. Proc. 44:364. • William, C. , Wilson, W. , and Burrin, J. 1996. Influence of carbohydrate supplementation early in exercise on endurance running capacity. Med. Sci. Sports Exerc. 28:1373-1379. • Tsintzas, O. , Williams, C. , Singh, R. , Wilson, W. , and Burrin, J. 1995. Influence of carbohydrate-electrolyte drink on marathon running performance. Eur. J. Appl. Physiol. 70: 154-6. • Sherman, M. 1995. Metabolism of sugars and physical performance. Am. J. Clin. Nutr. 62:228S. • Coggan, A. , and Swanson, S. , 1992. Nutritional manipulations before and during endurance exercise: effects on performance. Med. Sci. Sports Exerc. 24:S331.