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Introduction
An ergogenic aid is an external influence, both legal and illegal which positively affects sporting performance. The legality of ergogenic aids is controlled by the World Anti-Doping Agency (WADA) (Kayser et al, 2007). Buck et al (2013) stated that a legal ergogenic aid in sport can provide athletes with additional opportunity to enhance their performance beyond training alone. There is therefore growing interest for both coaching staff and performers themselves in foods and other legal aids which have a beneficial effect on sporting activity, as well as shorten recovery periods resulting in a faster return to training (Reid, 2013). Intake of nutritional ergogenic aids such as carbohydrates are consequently used to elevate performance levels in a variety of ways such as reducing the effects of fatigue. (Alireza et al, 2016)
Glucose (a form of carbohydrate) is the primary fuel source respired by the body for energy. During exercise, the stored form of glucose, known as glycogen, is converted back to glucose and used for energy (Berger, 2016). Cermak & Loon (2013) stated that performers partaking in prolonged exercise lasting 60 minutes or more should eat 60 grams of carbohydrates per hour but that well trained endurance athletes can metabolise up to 90 grams per hour. This literature review will look to analyse how useful carbohydrates can be as an ergogenic aid by identifying whether performance can be improved through changing the volume of carbohydrates consumed before performance, as well as the preferred form of exogenous carbohydrate consumed during performance.
Main Body
Consumption of Carbohydrate through Diet
Lima-Silva et al (2013) Presented a study in order to examine the effects of high and low carbohydrate diets on performance levels and the contribution of the aerobic and anaerobic energy systems. 6 male participants were told to eat as they usually would for 48 hours followed by a maximal cycling exercise at 115% maximal oxygen uptake right up until exhaustion. They were then given 72 hours recovery followed by another 48 hour period of either a diet high (70%) or low (25%) in carbohydrate content. The same cycling test was then repeated and results gathered. The results obtained showed that the low carbohydrate diet reduced the time until exhaustion, and therefore showed that these participants had less available energy when performing maximally. This test showed that by having a diet low in carbohydrates, individuals found themselves reaching exhaustion sooner than they would using their usual diet. This suggests that carbohydrates are an important source of energy during maximal cycling events, in order to delay the onset of fatigue. The results obtained are only based on male performance and so it could be argued that females may perform differently under a similar situation.
This was supported by Maffetone and Laursen (2017) who conducted a study on a 38 year old female Triathlete. They reduced her training time from 30 hours a week to 18 hours a week, increasing to 24 hours over a 6 week training programme. They also reduced her carbohydrate intake from 73% (475g) to 12% (78g). After the 6 weeks, the participant stated she felt she had more energy during and between training sessions, as well as less perceived fatigue and hunger. Her cycling output increased by 20 Watts and running speed increased from 12km/s to 15km/s. They concluded that by reducing training load and carbohydrate consumption and increasing fat intake prior to performance you can improve health functions and increase performance levels in elite triathletes. This study could be seen as unreliable due to the fact that it only tests a single individual on one occasion.
Therefore, it could be argued that other factors such as the type of training being conducted may have affected the result. Some of these findings are also subjective as the performer perceives her hunger and levels of fatigue rather than numerical statistics to support these claims. Similar to Maffetone and Laursens study, Podloger and Debevec (2016) also carried out a study on a single athlete in order to identify whether a low carbohydrate diet produces the same level of performance as a high carbohydrate diet. This male athlete consumed a 14 day low carbohydrate diet and was then put through a serious of tests. The tests involved a moderate intensity (65% VO2 max) and maximal intensity (90% VO2 max) of constant cycling. They were then repeated after a 14 day high carbohydrate diet. Minute ventilation was recorded and oxygen uptake assessed via calorimetry of blood samples to determine glucose and lactate concentrations. This test again found that the diet rich in carbohydrates resulted in a 9% faster time to exhaustion during moderate intensity, but an 3% increase in time toexhaustion during maximal intensity. These results show that at lower intensities, a diet rich in carbohydrate is less effective than a low carbohydrate diet. This is due to the fact that there is more oxygen available to the working muscles so fats can be oxidised rather than carbohydrates.
To oppose this, Lima-Silva et al (2014) conducted another test to identify the effects of a high carbohydrate diet on running performance in adolescent boys. 19 trained individuals performed a 10 minute run at 65% VO2 max to determine Respiratory exchange ratio. the test results showed that consuming a carbohydrate rich diet enhanced performance in the 10000 metres compared to that of a fat rich diet. This further suggests that due to higher intensity, carbohydrates are acting as a primary fuel source and supply the body with energy for respiration, therefore reinforcing the idea that carbohydrates can act as an ergogenic aid if consumed in excess during the dietary phase prior to performance.
Consumption of Carbohydrate during Performance
A study conducted by Gui et al (2017) found that female distance runners improved their performance when ingesting a carbohydrate electrolyte solution (CES) during a 21km run. In a randomized crossover design, the 11 participants consumed a CES or a sweetened placebo at a rate of 150ml per 2.5km. This tested was repeated on 3 different occasions with at least 28 days in-between each race. Results showed that those who consumed the CES had slightly shorter running times than those with the placebo (129.6 ± 8.8 minutes and 134.6 ± 11.5 minutes respectively). These resultsshow that by consuming carbohydrates during activity, performance levels can be elevated as glycogen stores arent used up and instead the exogenous carbohydrate acts as the energy source.
To further identify whether different carbohydrate-rich drinks produce different levels of performance, Dobson and Seery (2016) conducted a test involving a carbohydrate-protein (CP) drink and chocolate milk (an everyday drink rich in carbohydrates) They wanted to assess whether some drinks are better at producing top results than others. Eight male collegiate cyclists completed 2 experimental trials, separated by 1 week. Each activity consisted of a glycogen depleting trial, a 4 hour recovery phase and a 70% VO2 Max cycle until exhaustion. 2 hours into recovery performers consumed either a chocolate milk drink or a CP drink, Blood lactate and Glucose levels were taken during rest as well as heart rate measurements during the cycle. Results showed there was no significant difference between the two beverages suggesting that carbohydrate specific drinks will not perform more effectively than household chocolate milk, This also suggests that any drink high in carbohydrate concentration can be used as an ergogenic aid in sport. However a limitation of this experiment is that only the two types of beverage were consumed which means other drinks may have a different effect
Carbohydrates can be consumed during performance in the form of Gels, drinks and bars. There is therefore interest into which exogenous carbohydrate has the most benefit on performance. Sareban et al (2016) conducted a study on 9 well trained triathletes, in order to identify weather a gel and liquid form of carbohydrate affects performance and comfort and which is the better option. The study found that performance didnt improve between the two forms of exogenous carbohydrate however, 7 of the 9 participants stated they experienced gastrointestinal discomfort when using the gel. This may cause a hinderance to performance levels as the discomfort may result in pain after long periods of time causing distraction or even the inability to perform. This may therefore show that ingesting carbohydrates in the form of a liquid may be the optimum way of increasing glucose in the body for energy during performance.
A similar study was also carried out by Guillochon and Rowlands (2017) however this study included bars and Mixed exogenous carbohydrate sources as well as gels and drinks. The participants of the study reported increased levels of nausea and stomach cramps with higher perceived exertion when using the bars as an exogenous carbohydrate, rather than the gels. These results contradict the previous test by Sareban et al (2016) as there were no changes in discomfort levels when using gels or liquids. This may be because a different form of gel and liquid had been used as well as the activity being focused on male cyclists rather than triathletes.
The pain from the previous test may have come during the swimming phase of the triathlon and so cyclists are not negatively affected in this way. Rather than consuming food during exercise, there has been increased interest into carbohydrate (CHO) oral rinsing on performance in activities lasting sub 60 minutes. Clarke et al (2017) performed a test on 12 males to identify if a CHO rinse will improve their results In a variety of maximal intensity exercises. His results found that oral CHO rinsing improves 10m sprint times, bench press and squat repetitions. These results suggest that by using CHO rinsing as an ergogenic aid in morning maximal intensity exercise, performance levels may increase without the need to use other exogenous carbohydrate aids.
Oral CHO rinsing was again tested with different concentrations on a 1 hour cycle ergometer by James et al (2017). 11 male cyclists completed the 1 hour time trial 3 times. Every 5 seconds they rinsed their mouths with either a 7% concentrated CHO solution, a 14% or a placebo. Heart rate was recorded at every 12.5% of the trial and gastrointestinal discomfort every 25%. Their results showed that the 7% CHO solution improved cycle times compared to the placebo, but increasing the concentration had no effect. This may therefore suggest that there is a limit to the amount of CHO oral rinsing that the body can utilise and surpassing this threshold provides no extra benefit. However, More concentrations may have been used in order to recognise this pattern.
Conclusion
To conclude, The data found regarding carbohydrate consumption prior to performance shows that performance levels in maximal intensity prolonged exercise can be improved. The data to show otherwise has only been tested with minimal participants across a narrow range of ages, however the data identified also shows how as intensity of exercise decreases, there is less requirement for carbohydrates as the primary fuel source and so carbohydrates as an ergogenic aid wouldnt be as effective. It was also found that the majority of athletes preferred consuming energy drinks over other forms of exogenous carbohydrates as they resulted in no stomach pains. This allowed participants to focus on performing to the best of their abilities and so yielded increased levels of performance. Bars and Gels on the other hand were reported to give participants (particularly triathletes) Increased levels of Nausea and higher rates of perceived exertion with no actual improvement to performance levels, however this may have just been due to the type of bars or gels being used as well as the types of activity being performed and the combination of food they had eaten prior to these exogenous carbohydrate sources. There hasnt been enough data gathered to truly state which source of exogenous carbohydrate gives the best results as there hasnt been a large number of participants tested and so the data isnt yet reliable.
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