Supplements and Ergogenic Aids for Cycling Athletes - Literature review Example

? Literature review of supplements and erogoeinc aids used by cycling athletes Professional cycling is among the most physically demanding sports with a combination of extreme duration, intensity and frequency of the physical demand. Professional cyclists have approximately 100 race-days in a year with races ranging from 200 to 3000 and more kilometers on different terrains with different requirements for physical endurance, terrains like roads, mountains, cross road etc. (Jeukendrup et al. 2000). In a study conducted by White et al. 1984 the measured the physiological impact of 24 hours cycling race on a highly trained cycling athlete (23 years old, weighting 73 kilograms and 195 centimeters tall). The cyclists covered 694 kilometers at an average speed of 28.9 kilometers/h with average oxygen consumption of 55 percents of the VO2 max. It was estimated that the cyclists spend approximately 82 680 KJ of energy during this event. From this total energy spend in the race 54 percents were obtained during the race with intermittent ingestion of liquids, energy and sports drinks and other sources. Based on this approximately 46 percents of the total energy was provided by the intrinsic stored energy (in a form of glycogen, fats, proteins etc.) form the cyclist. As a result of this at the end of the race cyclist loosed 1.19 kilograms of body weight. This example shows that energy demands during long lasting cycling events are extreme. It is estimated that they are 3 times greater than the highest recorded energy demand in a heavy industry worker. There are many parameters that are used in order to measure the level of physical demands in one exercise and in the same time to evaluate the physical condition of the athlete. One of them is VO2 max. It is defined as maximum oxygen consumption in one athlete or peak oxygen intake in a period of time during intensive exercise. It is the maximal measured capacity of the organism of the athlete to use oxygen during one physical exercise and is measured in liters of oxygen in minute or milliliters per kilogram body weight in minute. It is a measurement of the ability of the organism to use aerobic system to produce energy. In order to better understand the implication of this measurement we must note that the organism has several systems of energy production that in essence is one complex system, composited of the ATP system, anaerobic system of glycolisys and aerobic system or mitochondrial respiration. End product of all systems is ATP (adenosine three phosphate) which is the main energy source for the cell metabolism. During low level exercises human muscles almost exclusively use aerobic mitochondrial metabolism as for energy production. It is much more effective process of energy production because from one molecule of glucose it produces 30 molecules of ATP. Because of this during low levels of exercise muscles use mitochondrial respiration. But we must understand that the metabolism of glucose is conducted both by aerobic and anaerobic metabolism. In the anaerobic metabolism glucose is converted to pyruvate which is than metabolized oxalate and oxalate it then finally metabolized in the mitochondria to CO2 and water producing 30 molecules of ATP. Now in low level exercises almost all glucose is converted to pyruvate and all pyruvate is metabolized to CO2 and water using this aerobic metabolism in the mitochondria. VO2max is actually measurement of this ability of the human organism to use aerobic processes to produce energy. In order to measure VO2max the intensity of the exercise is gradually increasing until the oxygen consumption reaches maximal values (Niels et al. 2004). It is important measurement because by aerobic metabolism energy is used much more effectively and therefore athletes can produce better results in a long lasting low level exercises. However in the case of extensive exercise (for example during a sprint before finish or very steep slope on the mountain) there is a demand for more energy and more glucose is metabolized to pyruvate. At one point mitochondria are no longer capable to use all of the pyruvate and some of it starts to be converted to lactate, which than enters the blood and muscles. This lactate is than utilized by the muscles, liver, heart and other organs in the body by the anaerobic metabolism of glucoses. Anaerobic metabolism of glucoses is much less effective than aerobic mitochondrial breathing and produces only 2 molecules of ATP from one molecule of glucoses (compared to 30 molecules of ATP in aerobic metabolism of glucoses), but the energy can be produced much faster. This point when the blood concentrations of lactate are starting to rise above the normal levels is recognized and called lactate threshold point (Bassett and Howley 2000). Actually we can define 2 distinct lactate threshold points. The first one is also called “aerobic lactate threshold” and is measured when the levels of lactate start to rise in the blood. The second is also called anaerobic lactate threshold and is defined as maximal steady state of lactate in the blood during intensive physical exercise that can be sustained for some period of time, or in other words the process of production and elimination of lactate is at equilibrium and any increase in physical exercise will start to elevate the levels of lactate in the blood which will result in drastic decrease in the performances of the athlete (Bassett and Howley 2000). This reducing of performances of the athlete in exercises above the anaerobic threshold is due to a several factors. Elevated concentrations of lactate (which has properties of weak acid) elavets the acidity of the blood (Ph). The organism then tries to regulate this elevated acidity of the blood by activating the puffer systems in the blood (mostly bicarbonate puffer system) and the end product of this process is production of CO2 that is than eliminated through the lungs. This is noticed as drastic increase in the respiration and more “heavily” breathing by the athlete (Robergs 2001). On the other hand increasing levels of lactate and other degrading products of metabolism (glucose 6 phosphate, ADP or adenosine di-phosphte-the end product of used ATP and other products) have effect on the Ca2+ channels on the muscles (including heart muscle), effect the function of actomyosin ATPase (important in the process of muscle contraction) and other mechanisms that result in fatigue, weakness, dyspnea, tachycardia etc. (Steele and Duke 2003) (Cooke and Pate 1990) (MacIntosh 2003). Based on the above mentioned mechanisms we can conclude that in order cyclists to produce maximal result in one sport event they must physically conditionate their body in order to produce maximal performance in different stages of one race. As we mentioned above cycling race is commonly constituted by long lasting intensive effort with periods of extensive additional effort like sprints, upslopes, frontal winds etc. Therefore the organism of the athlete must be able to optimally use both aerobic and anaerobic mechanisms of energy production, they must preconditionate their organism to be ready to the intensive effort during the race by different mechanisms. There are studies that show that improving VO2max in cyclist lead to significant improvements in cycling economy and mechanical efficacy of the cyclist. Improving VO2max in cyclists result in usage of much more economical aerobic system of energy production and delays the appearance of the aerobic lactate threshold (Greg et al. 2004). There are many methods to improve the aerobic metabolism or VO2max. Short periods of intensive exercise close to VO2 max is reported to significantly improve VO2max. The effect of this type of exercise is much greater compared to continuous low level exercises (Rognmo etl al. 2004) (Wisloff et al. 2007). There are studies that show that high altitude training is improving VO2max in long distance runners and cyclists, a method that is commonly used for conditioning professional athletes (Saunders et al. 2004) (Levine and Stray-Gundersen 1997). But professional cyclist must be able to prduce extra energy that is needed at the peaks of intensive race, in the finish, in the upsloaps etc. Improving aerobic and anaerobic lactate threshold is the key elements in professional sport including cycling. There are many methods to improve the anaerobic threshold. One of them is gradually increasing the training over a longer period of time and the intensity should not be more that 10-20 percent incensement per week (Bompa 1999). Other method is repetitive training at the lactate threshold point. Some studies found that in trained individuals lactate threshold starts at 80-90 percents of the heart rate reserve (the maximal measured heart rate during intensive exercise in one individual). The same lactate threashold appears at 50-60 percents of the heart rate reserve in normal, untrained population. It is found that this can be much improved with training at the lactate threshold level, where the athlete will be able to sustain longer periods of extreme physical activity needed in some parts of a race (Weltman 1995). Carbohydrate loading Even though physical condition is the most important in achieving high professional results, professional athletes use additional ergogenic aids in order to achieve edge in front of the competition. Usage of dietary supplements is one of the most important measures in order to prepare the athlete before important sport event. There are many techniques that are used in order to achieve preconditioned state in the organism of the cyclist in order to optimize the physical condition before a race. There are a many studies that show that fatigue and weakness during a long range, intensive races is correlated with the appearance of hypoglycemia and depletion of glycogen reserves in the body. Feeling of fatigue is partly mediated by the brain and central nervous system by mostly is influenced by general metabolic factors where hypoglycemia is found to be one of the most important. During the events of continuous cycling with moderate intensity at VO2max levels of 70-80 percents the symptoms of fatigue are associated with very low levels of muscle glycogen concentrations (approximately 100 mmol/kg) and hypoglycemia (Bosch et al. 1993) (Kent-Braun 1999) (Nybo 2003). In order to understand this we must take into consideration some facts about muscle contraction. Muscles use ATP as energy source. In the first moments of high exercise event energy is mostly obtained from the deposits of ATP in phosphocreatine that is deposited into the muscle cells and can sustain muscle contractions for about 15 seconds. This energy is used in the start of the muscle exercise and is the first source of energy that is used regardless of the intensity of the exercise (Fleck and Kraemer 1997). After this initial event with prolonged activity muscles start to use other sources of energy. Muscles can use different substances for energy but mostly the energy obtained within the muscle is from glycogen and free fatty acids. At lower intensity work muscles as a source of energy mainly use fatty acids (in up to 70 percents) and carbohydrates (in about 30 percents). However this is only true for low level exercises and not in higher intensity exercise that is present during a sport event like cycling, when the muscles as a source of energy predominantly use carbohydrates as a source of energy (Jones et al. 1986). This is because process of oxidation of carbohydrates is much faster and more effective compared to fatty acids. As a comparison oxidation of carbohydrates produces 120 kcal of energy from mole of oxygen, compared to 100 kcal from fatty acids. (Romijn et al. 1993). During intensive physical exercise the main source of carbohydrates in the muscles is glycogen that is stored in the liver and the muscles. The importance of this glycogen storage can be seen by the fact that there are studies that show that fatigue and muscle weakness are significantly associated with low levels of glycogen in the muscles as mentioned above (Bosch et al. 1993) (Kent-Braun 1999). A normal untrained individual in a period of normal diet stores about 100 grams of glycogen in the liver and additionally about 280 grams of glycogen in the muscles (Campbell et al. 2006) (Miwa and Suzuki 2002). We must note here that glycogen stored in the liver can be used by other organs after is enzymatically broken down to glucose and released in the blood. However glycogen in the muscles can only be used by the muscle cell where it is stored. Now knowing this fact, in a prolonged exercise if no additional carbohydrates are ingested muscles in the body will be predominantly dependent on this stored glycogen in the muscles and the liver. Knowing the fact that oxidation of glucose at 70-80 percents of VO2max exercise intensity is about 1 gram per minute we can conclude that untrained individual with this level of exercise will deplete his glycogen levels in about hour and a half resulting with heavy fatigue and muscle weakness or the so called “ hitting the wall” moment (Pedersen et al. 2008). This is because the levels of glucose in the blood are starting to decrease rapidly and are not able to be compensated by the glycogenolisys in the liver. Now knowing the importance of this stored glycogen in the body athletes before race tend to increase the levels of this stored glycogen in the body by a process called “carbohydrate loading”. There are many used techniques to achieve this but the process is composed from 3 phases which are prolonged intensive muscle exercise of the muscles with dietary restriction of carbohydrates and this is followed by a period of carbohydrate overload. Using this method in well trained athlete the glycogen storage in the body can be dramatically increased to approximately 880 grams of glycogen (160 grams in the liver and 720 grams in the muscles) (McArdle et al. 1999). There are many procedures for carbohydrates loading. In a protocol designed by Costill et al. 1990 the carbohydrate loading is in 2 phases. The first or glycogen depletion phase lasts 3 days. In this phase athletes are subjected to physical exercise at 70 % of VO2max on a cycle ergometar and in the same time they are subjected to low carbohydrates diet (about 50 %) and increased fat and protein diet in order to deplete the glycogen levels within the leg muscles. This is important step in the so called super compensating the glycogen levels in the muscles. Glycogen synthesis in the muscles is produced by glycogen sythetaze enzyme which is present in inactive D-form and active I-form. With a process of depletion of the level of glycogene in the muscle and then resynthetyzing the levels of active forms and the activity of the enzyme increases significantly resulting in increased muscle glycogen concentration or glycogen super compensation (Jansson and Kaijser 1987) (Price et al. 1994). In the second repletion phase athletes are subjected to high carbohydrates diet (about 80 %) and lof fat and protein diet in order (Costill et al. 1990). This is the classic carbohydrate loading but the regiment of intensive training and diet can result in fatigue and gastrointestinal problems in the athletes. In a study conducted by Coyle et al. 2001 where the cyclists were feed with high concentration carbohydrates diet (88%) training 2 hours a day for 7 days at 70% VO2max, they produced very high muscle glycogen concentration without the glycogen depletion phase. There are studies that show that high carbohydrates diet after very intensive exercise (150 second at 130 % of VO2max) can create super compensated glycogen concentrations in the muscles in 24 hours (Fairchild et al. 2002). Also it is important to note that taking carbohydrates during the race is also important because during long lasting cycling events glycogen storage is not sufficient to complete the race (White et al. 1984). Caffeine as a supplement There are many studies that show that caffeine has important and beneficial effect in the preparation for and during intensive high intensity workout (McArdle and William 2010). There a number of positive effects that are broadly recognized by athletes of ingesting caffeine prior and during sports events. Mainly the positive effect of caffeine is believed to be due to 2 mechanisms of action: positive simulative effect on the brain and direct effect on the body metabolism. There are studies that show that caffeine can reduce the perception of fatigue by the brain and improve the performance in long lasting sports events. There are studies that show that caffeine have direct influence in the brain where is capable to antagonize the effect of adenosine that is resulting in higher concentrations of stimulatory neurotransmitters (Davis et al. 2003).This is believed that increase the alertness of the athlete and reduces the perception of effort and fatigue that results in better results in high intensity endurance events. The psychological effect of caffeine can be also explained by the fact that caffeine is sympathetic stimulant. There are studies that show that caffeine increases the blood levels of epinephrine and norepinephrine, which are (Van Soeren et al. 1993). In a study conducted by David et al. 2007 it was found that ingesting caffeine after intensive cycling that produced depletion of glycogen in the muscles, resulted in much faster glycogen resynthesis and higher concentrations of glycogen in the muscles of athletes that consumed carbohydrates and caffeine versus athletes who just consumed carbohydrates. There are studies that show that caffeine can alter the calcium concentrations within the muscle cells and therefore improve the muscle strength of contraction (Lindinger et al. 1993). What is more important there are studies that show that caffeine has specific effect of increasing the endurance of the muscles and increasing the muscle strength in all muscles in the body, but most exclusively on leg extensor muscles, muscle that are most important in cyclists (Warren et al. 2010). Another often mentioned mechanism of registered positive ergogenic effect of caffeine is the ability to modify fat metabolism. Caffeine is able to increase the concentration of free fatty acids in the blood and increase the fat oxidation in the first minutes of exercise. This leads to decreased activity of glucose 6 phosphataze and glycogen sparing. In a study conducted by Spriet et al. 1992 conducted on eight subjects cycling to exhaustion at 78 % VO2max, it was found that ingesting caffeine reduced the glycogeolisis for 55 % during the first 15 minutes of the exercise. This spared glycogen was than available in the later stages of the exercise and in the subject who ingested caffeine the exhaustion appeared much later than the control group. Creatine supplements Creatine is a molecule that is naturally found in small quantities in the brain, liver, kidneys and other organs in the body, but most of the concentration of creatine in the body, or 95 % is concentrated in the muscles (Greenhaff 1997). Creatine in the body is supplied by two mechanisms. It can be synthesized in the liver and kidneys from amino acids arginine, glycine and methionine or it can be supplied by exogenous sources like eating fish, meat and other food (Bemben and Lamont 2005). Creatine or phosphagene system is one of the most important systems in the body for producing ATP. ATP is composed from amino acid adenosine, one molecule of ribose and three high energy phosphate groups. The energy stored in these phosphate groups is only form of energy that can be used by the muscles in the body for muscle contraction. The storage of ATP in muscle cells in sufficient for just a few seconds of muscle contraction. During a muscle contraction ATP is hydrolyzed to ADP and phosphate and the energy released by this process is used for a muscle contraction. There are 3 systems for resynthesis of ATP from ADP. Creatine or phosphagene system is one of them and is the fastest method for resynthesis of ATP in the cell (Bemben and Lamont 2005). Storage of creatine in the muscle cell can provide energy for about 15 seconds, what is fund to be the most important source of energy in high intensity, short duration exercises. In the organism creatine is found in two forms free creatine (about 40%) and phosphocrratine (about 60%). In an average 70 kg men the total creatine in the body is estimated around 120-140 grams and the daily turnover of creatine is about 2 grams. This turnover is partly replaced by the endogenous synthesis and partly by ingestion different foods. There are studies that show that levels of creatine (both free and phosphocreatine) in the muscles can be increased with creatine supplementation what increases the performance of high intensity intermittent exercises (Balsom et al. 1994). It is found that ingesting 5 to 20 grams of creatine a day as a food supplement increasd the concentrations of creatine in the muscles and is safe and doesn’t cause any negative effects in the body and in the same time producing better performances in shorter high intensity exercises. This improvement is predominantly present in activities like jumping, sprint or cycling (Bizzarini and De Angelis 2004) (Bemben and Lamont 2005). There are many studies that show that creatine loading is improving the sprint performance in cycling. In a study conducted on elite, professional cyclists in well designed and standardized endurance protocol it was found that creatine loading with 25 grams of creatine for 5 days improved their intermittent sprint capacity at the end of endurance exercise to fatigue (Gill et al. 2004) (Vandebuerie et al. 1998). Proteins and amino acids Amino acids and proteins are the building blocks of the body and they are essential in synthesis of enzymes, muscle fibers, hormones etc. Athletes due to their intensive physical involvemed require additional and specific needs for proteins and amino acids. It is estimated that active athletes should intake between 1.3 and 1.8 grams of proteins per kilogram of bodyweight a day what is about twice as much is recommended for a normal adult involved in normal everyday activity (Lemon 1998) (Kreider 1999). This is why ingesting enough proteins is very important in the diet of any athlete. Ingesting more proteins than the daily requirements for the athlete is not shown to improve muscle strength (Tarnopolsky et al. 1992). However it is found that ingestion of whole proteins that are found in everyday’s food (eggs, mils, meat) is not as effective as amino acids in inducing anabolic processes in the body when they are consumed before exercise (Tipton et al. 2007). The benefit of whole protein ingestion and carbohydrates is found by many studies and it is shown that pre and post exercise consumption of this mixture produces anabolic effect in the body and in the same time reduces the catabolic effect on the muscles (Carli et al. 1992). It was also found that ingesting a mixture of proteins and carbohydrates post exercise promotes fster glycogen synthesis and improves recovery after vigorous exercise (Roy and Tarnopolsky 1998) (Berardi et al. 2006). Specific amino acid supplements are found to have more specific benefit for the organism and performance of the athlete. It is found that specific amino acids like arginine, lysine and ornitine can stimulate growth hormone release when are administered parenterally or orally in the organism. Many athletes today consume these amino acids before exercise believing that this will produce greater muscle mass and improve the anabolic profile in their body (Chromiak and Antonio 2002). These amino acids cn also increase the levels of insulin and corticosteroids that can also have a beneficial effect on muscle gain and strength (Kreider et al. 1993). Another group of amino acids called branched chain amino acids (BCAA’s) constituted form valine, leucine and isoleucine, is found to have many benefits in the organism of the athlete. BCAA’s have anabolic effect on the protein metabolism, decreasing the rate of protein degradation. Also during recovery from long lasting endurance exercises and sport events BCAA’s hav anabolic effect on the muscles and stimulate muscle growth. This is believed to be due to changes in signaling pathways in protein synthesis that are mediated by these amino acids (Blomstrand et al. 2006). BCAA’s have role in reducing the central nervous system fatigue. Central fatigue is manifested due to changes in the 5-hydroxytriptamine (5-HT) levels in the brain. The rate of synthesys of 5-HT is dependent of the transport of tryptofan across the blood-brain barrier. During prolonged exercise BCAA’s are taken by the muscles in larger concentrations to be used in the oxidative processes. This is resulting in depletion of the BCAA’s concentration in the blood pull. Not this is important because the transport of tryptofan in the brain is mediated through the same amino acid carrier as for the BCAA’s group. This will therefore result in greater tryptofan/BCAA’s ratio in the blood and greater concentrations of tryptofan in the brain that is a factor for developing central fatigue (Blomstrand 2006). Bicarbonate loading Bicarbonate loading is another very popular and common ergogenic supplement that is used by athletes, more commonly as an aid in high intensity and short duration events. There are studies that show that bicarbonate loading is showing some improvements in the performances if they are taken before the event (Burke and Pyne 2007). During intensive exercises muscles are not able to oxidize the glucose using the aerobic metabolism as it was explained above in the text, and some of the glucose is metabolized through the anaerobic pathway producing lactic acid. One of the mechanisms in our body to reduce the increased acidity in the blood because of this is the activation of bicarbonate puffer system. However this system has limited capacity and the end result is increased lactic acid in the blood, increased respiration and fatigue (Robergs 2001) (Steele and Duke 2003) (Cooke and Pate 1990) (MacIntosh 2003). The positive effect of bicarbonates loading is that increased levels of bicarbonates in the blood are able to prevent the rise of acidity in the blood and prolong the onset of muscle fatigue. This system is effective in the first 1-7 minutes of high intensity exercises that result in predominantly anaerobic metabolism, therefore bicarbonates loading in cycling can only be effective at the start of the race or during short, high intensity periods at VO2max between 80 and 125 percents (McNaughton et al. 1999). There are several methods of bicarbonate loading. Acute loading is produced by administering 300 mg NaHCO3 per kilogram body weight before the sports event and this is found to increase the total power output up to 8.7 percents. It is important to note that this improvement was only found in intensive exercises ranging between 1 and 7 minutes, and no positive effect was found in exercises shorter than 1 minute and longer than 7 minutes (McNaughton et al. 1999) (Kozak-Collins et al. 1994) (Verbitsky et al. 1997). Chronic bicarbonate loading is conducted by taking 500 mg tablets of NsHCO3 every 4 hours a day during 5-6 days. For many sports chronic bicarbonate loading can be of greater benefit because the body can store the extra bicarbonates that can be used during the exercise. There are studies that show that this chronic supplementation protocol with repeated dosing over several days is increasing the buffering capacity of the blood and this effect is lasting at least 24 hours after the last dose of bicarbonates (McNaughton and Thompson 2001). However there are some concern regarding usage of bicarbonate loading. Gatrointestinall distress I often accompanied with usage of this supplementation with symptoms like nausea, vomiting, bloating etc. This symptoms can be avoided by ingesting larger quantity of water pr taking NaHCO3 in a form of gelatin tablet. Also bicarbonate loading, especially chronic bicarbonate administration and the performace after this period is actually reduce (McNaughton and Thompson 2001). 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