The Effects Of CHO
A clinical, controlled study was conducted on twelve male participants after an intensive 2 hour football training session to measure the effects of CHO on the distance run in twelve minutes. The CHO was orally ingested in the form of a drink, with concentrations of 0%, 5% and 10%, according to subjects’ body weight. The results are inconclusive. It is suggested, however, that the relation between CHO and distance run is positive, based on statistical inference.
The report includes a comprehensive literature reviewcovering twenty years of research into the area and a comparativecritique for the purposes of future study. A number of suggestions fordiffering kinds of test are made. The effects of CHO fail Mauchly’stest of sphericity since the subjects who ingested a 10% CHO fluid didnot run a longer distance than those who ingested a 5% fluid, althoughthey were able to run further in twelve minutes in comparison to thecontrol group, who ingested a placebo, after the 3 hour recoveryperiod.
Key words: Carbohydrate, “Cooper Run Test”, glucose maltodextrin, football
The Cooper run test has been used for over a quarter of a centuryto assess athletic performance. It is based on the work of Cooper(Cooper 1968) who found that there existed a positive correlationbetween the body’s use of oxygen and the distance run in a fixed timeperiod. Different periods of running were suggested, with mostcontemporary studies making suggestions of nine, twelve and fifteenminutes. A relatively short period of athletic activity is practicalfor a study of this type where a balance must be struck betweenincluding as many subjects’ as possible and being able to measure thesubjects’ performance.
Carbohydrate (CHO) has a significant effect on athletic performance.In this study, the effects of an orally-administered CHO drink weremeasured on football players testing on the Cooper Run Test after anintensive two hour training session. There were twelvestudy-participants, all active and healthy males, who took part in theexperiment. It was designed to measure how CHO changes the performance,if at all, of the study-participants and the experiment was conductedwith standard double-blind, randomised, placebo-controlled measure. Thestudy is of clinical standard.
If the experiment had been inconclusive as to the effects of CHO onthe Cooper Run Test, the results would still have been important forphysiology as an academic discipline, because a considerable amount ofresearch has been conducted on CHO. This report will include a thoroughliterature review of existing research and will hopefully be acontribution to scientific progress. We will see how existing researchhas varying conclusions; therefore at the least, this experiment willclarify issues that need to be addressed for future research in thisarea.
The Cooper Run Test is a deliberately simple experiment that measuresthe distance run in a twelve minute period. It is an excellent testbecause its simplicity minimises extra-experimental, or uncontrolled,variables. All that is measured is distance and time. There are othertests available that also measure the effects of CHO on the Cooper RunTest; however we believe that the Cooper Run Test is the best.Nevertheless, other tests might be mentioned during the course of thisreport, for the purposes of thoroughness.
CHO, to use its chemical definition, is a mixture of carbon, hydrogenand oxygen, whose combination in various degrees makes up thecarbohydrate molecule. An example of a carbohydrate molecule is sugar,such as lactose, dextrose, fructose or common refined sugar, sucrose.Sugar is made from sugar beets and in its most common form is canesugar. It is easy to add to drinks because it dissolves thoroughly.
The importance of research into the effects of CHO is of considerable economic importance, because the market for CHO drinks is large, with expenditure on these drinks often justified for reasons of performance improvement. If this study were to show that CHO had no effect on participants’ performance in the Cooper Run Test, then we would have to ask further questions about the CHO market. Focussing on the research will enable us to agree or disagree with the reality of economic expenditure on these beverages. CHO may or may not have an effect; therefore we will state the research hypothesis.
The hypothesis is:
CHO has an effect on performance in the Cooper Run Test.
This hypothesis can either be confirmed or rejected, or the results from the experiment can be inconclusive. Which conclusion the results show will be discussed below, but first the methodology of the experiment we will describe, including the null hypothesis.
Review of Literature
Researching this body of scientific knowledge, we have identified anumber of repeating themes from research journals and reports that areuseful to us in this review. Two themes are carbohydrates and researchmethodology; the latter can be further subdivided into quantitative and qualitative. For this review of literature we will focus on how current scientific research treats the matter of carbohydrates first.
Millard-Stafford says that “carbohydrate in a variety of forms(glucose, glucose polymer, fructose or sucrose) may provide additional energy to be utilised during exercise.” (Millard-Stafford 1992) Sheargues that during prolonged exercise muscle glycogen and / or bloodglucose may decrease markedly and thus coincide with fatigue. She does not conclude on the optimal carbohydrate, or its optimal concentrationin a beverage, however.
The influence of a high concentration of carbohydrate is tackled by Fallowfield et al., but they conclude that “there is no additional performance benefit obtained by increasing the amount of carbohydrate given.” (Fallowfield et al. 1997). In their study, nine men and eightwomen performed two endurance treadmill runs of 90 minutes duration where subjects consumed either an isotonic sports drink (6.9%carbohydrate; 1.0g carbohydrate per kg body weight) or a concentrated carbohydrate drink (19.3% carbohydrate; 3.0g carbohydrate per kg bodyweight), consumed at the start of recovery and two hours later.
Carbohydrate supplementation and concentration was similarly studiedby Wong et al. They said that “ingestion of 50 grams of CHO immediatelyafter prolonged exercise, and hydration with a placebo solution,results in a similar endurance capacity, after a 4 h recovery, asingesting 3 times more CHO (167 grams. CHO) over the same period.”(Wong et al., 2000) Nine men were used to examine the effect ofingesting different amounts of CHO during 4 hour recovery fromprolonged running on subsequent endurance running capacity whensubjects were fully hydrated. This study concentrated on endurance running and the role of carbohydrate on short-term recovery.
The effect of carbohydrate marathon running performance was studied byTzintsazl et al. “Seven endurance-trained runners completed three 42.2km treadmill time-trials which were randomly assigned and 4 weeksapart. On each occasion the subjects ingested 3 ml per kg body weightof either water, a 6.9% CHO solution, or a 5.5% CHO solutionimmediately prior to the start of the run and 2 ml per kg body weightevery 5 km thereafter.” (Tzintsazl et al 1995) Their research showedthat the ingestion of a 5.5% CHO solution improves marathon runningperformance.
Brouns et al conclude that “a carbohydrate rich diet and the ingestion of carbohydrate drinks during competition is an important measure to maintain optimal performance capacity in soccer players.” (Brouns etal., 1989) Interestingly, this experimental report does not only focus on the fluid ingestion of carbohydrate, but includes dietarycarbohydrate. And it is relevant to football.
Carbohydrate acquires a branding in Murray et al.’s article: Gatorade.(Murray et al. 1989). These researchers conclude that Gatorade, at 6%,had the optimal level of CHO concentration. It was tested against 8%and 10% concentrations that did not provide performance benefits andperformance from any concentration of CHO did not occur if exerciseoccurred for less than one hour. For this reason, performancemeasurements were made after one hour of cycling, to measure theGatorade effect.
Following a two-hour bicycle ride to deplete muscle glycogen stores,subjects in Ivy et al.’s study consumed either a placebo with nocarbohydrate or fluids containing varying concentrations ofcarbohydrate. (Ivy et al. 1988) Whilst they qualified their conclusionsthat they were of relevance to those who exercise more than once a dayor to those who exercise on a daily basis, their results suggested animmediate effect of carbohydrate: “results suggested that carbohydratesconsumed immediately after and 2 hours after exercise can enhancemuscle glycogen restoration.” (Ivy et al. 1988)
Bilzon et al. affected an effectiveness study on the short-termrecovery of a carbohydrate-electrolyte solution from prolonged constantpace running in a warm environment. (Bilzon et al. 2000) Thirteen malevolunteers completed two trials at least seven days apart with theassumption that recovery from prolonged exercise “involves bothhydration and replenishment of endogenous carbohydrate stores”. (Bilzonet al. 2000) They concluded that “provided that an adequate hydrationstatus is maintained, inclusion of carbohydrate within an oralhydration solution will delay the onset of fatigue during a subsequentbout of prolonged sub maximal running in a warm environment.” (Bilzonet al. 2000)
Sub maximal running means that the study participants are not exertingthemselves to the maximum of their athletic ability. Many studies bringthis approach to their research, including Wong et al (Wong et al.1998), whose paper about the pattern of fluid intake on short-termrecovery from prolonged, sub maximal running and subsequent exercisecapacity looks at the effects of carbohydrate during a four hourrecovery. Seven well-trained athletes took part in a study that was approved by Loughborough University ethical committee. Although it is amoot point whether the participants’ participation depended on this itis without question fantastic to note that ethics play a part in sportsscience. Lucozade sport was the fluid drunk. The results of this study focussed on the volitional aspects of carbohydrate ingestion, or as theresearch team said: “drinking a prescribed volume of acarbohydrate-electrolyte solution after prolonged exercise, calculatedto replace the body fluid losses, restores endurance capacity to agreater extent than ad libitum hydration during 4 h of recovery, eventhough the total volumes ingested were the same between trials.” (Wonget al. 1998) In a randomised, clinical trial such conclusions aredubious and fail to progress scientific knowledge, because ad libitumand the use of such pretentious phrases are ambiguous and confusing.
Wong et al. published a paper in 2000 that showed a significantimprovement in their research ability. (Wong et al. 2000) The influenceof different amounts of carbohydrate on endurance running capacityfollowing short term recovery, the title of the paper, is immediatelyto our literature review focussing on carbohydrates and quantitativemeasurements, or carbohydrate concentration. Their results “suggestthat ingestion of 50 grams of CHO immediately after prolonged exercise,and hydration with a placebo solution, results in a similar endurancecapacity, after a 4 hour recovery, as ingesting 3 times more CHO(approximately 167 grams CHO) over the same period.” (Wong et al. 2000)This research employed the services of nine male volunteers.Carbohydrate in the form of blood glucose was measured, as was seruminsulin, during the recovery period.
In 2002, Bilzon et al. published on glucose, a very specific andimportant carbohydrate whose effect on athletic performance must not beignored. A group of 11 healthy male volunteers exercised in a warmenvironment and it was the environment that was found to be the primary cause of incapacity instead of glucose availability. This study is vital for measuring seemingly external condition that were shown byexperiment to have considerable effect and it is one of the few studiesto include so many controlled variables. Interestingly Bilzon et al.assumed from the outset what research has shown to be the case, thatcarbohydrate intake improves humans’ capacity for exercise:“carbohydrate (CHO) ingestion during short-term recovery from prolonged running has been shown to increase the capacity for subsequent exercisein a warm environment.” (Bilzon et al. 2002)
Four hours recovery is a standard period in the existing literature, aconvention followed by Fallowfield et al. (Fallowfield et al. 1995),whose study also examined the carbohydrate concentration and itseffects on recovery. Twelve men and four women were divided into two groups. One was given a placebo and the other a carbohydrate-electrolyte solution. They concluded that drinking a 6.9%carbohydrate-electrolyte solution improved athletic ability followingexercise and a four-hour recovery period. “Thus, ingesting a 6.9%carbohydrate-electrolyte beverage following prolonged, constant-pacerunning improves endurance capacity 4 hr later.” (Fallowfield et al.1995). Fallowfield et al. do not specify the type of carbohydratestudy-participants were given.
In an early paper, Fallowfield published similar findings, in collaboration with other scientists. (Fallowfield et al. 1993)Carbohydrate intake and recovery from prolonged exercise investigatedwith an increased recovery period of 22.5 hours and a purely maleparticipation of sixteen volunteers. This paper showed that types of carbohydrate were of significant importance to exercise and to bodyfunction. “Blood glucose remained stable throughout T1 and T2 in both groups. In contrast, blood lactate, plasma FFA, glycerol, ammonia, andurea increased.” (Fallowfield et al. 1993) It was concluded that anisocaloric diet did not restore endurance capacity after 22.5 hoursrecovery but a high carbohydrate diet did. (Fallowfield et al. 1993)
Dennis et al. published a prescriptive research paper not limited tothe effects of carbohydrate, but widening the ambit to fluid,electrolyte and energy replacement. Since broken down carbohydratesbecome electrolytes there is something of an overlap between energy andelectrolyte replacement, however the authors point out that fluid isthe most efficient ingestion method for athletes and is part of anoverall nutritional strategy. “As only approximately 20 grams ofingested carbohydrate is oxidized in the first hour of exercise,athletes should probably consume 100 ml every 10 min of a dilute (3-5grams 100 ml-1) carbohydrate solution and thereafter increase thecarbohydrate concentration to approximately 10 grams 100 ml-1 to matchthe peak (approximately 1 grams min-1) rates of plasma glucoseoxidation.” (Dennis et al. 1997) This excellent research providesadvice to athletes which can be easily understood. The authors maintainan excellent balance of quantitative carbohydrate science, withapplication to the real world; for instance, there is advice to ingestcarbohydrate before exercise because carbohydrate ingestion “does notslow the rate of glycogen utilization in working muscle.” (Dennis etal. 1997) The conclusion of their research is about endurance, however,and they state that active muscles use glycogen at higher rates andthis decreases the indirect oxidation of non-working muscle glycogenvia lactate. (Dennis et al. 1997)
Study participants were twelve healthy male volunteers, averageage 24 years, average height 178cm, average weight 78kg. Volunteerswere presented with consent forms to sign and made aware of the CooperRun Test. A familiarisation trial was conducted one week before thestart of the experiment.
The apparatus was:
A trundle wheel
A stop watch
A data collection sheet.
Food weighing scales
A wall mounted height measure
Glucose maltodextrin drinks at the following concentrations:
0% CHO (placebo): 750ml water and 250 ml sugar free cordial;
5% CHO: 50g carbohydrate, 750ml water and 250ml sugar free cordial;
10% CHO: 100g Carbohydrate, 750ml water; and 250ml sugar free cordial.
It should be noted that all solutions were of identical taste. Thethree trials were randomised, counter-balanced and double blinded toavoid repeated measures designed to avoid subjects having apsychological advantage. In the interests of experimental accuracy, itwas vitally important that all subjects report to each trial in thesame physiological condition e.g. glycogen storage, each subject wasinstructed before the first test to record their dietary intake for 2days prior to the trail. Thereafter, the same procedure would followexactly the same pattern before each subsequent trial. Instructionaladvice was detailed to the participants to avoid strenuous exercise,caffeine, and alcohol for some twenty-four hours before the test.Eating at least 2/3 hours before each experiment was also arequirement. Prior to exercise in each case the solutions and amount offluid that needs to be used was calculated. Participants trained for 2hours at an intensive level.
This was followed by an ingestion of 5mls/kg body weight of fluid byeach participant followed by a 3 hour pre-testing resting period. TheCooper Run Test was conducted – the subjects had to run as far as theycould in twelve minutes. Distance covered was measured and recorded.
The statistical method used in this experiment was analysis ofvariance, an analysis of the variation in the outcomes of an experimentto assess the contribution of each variable to the variation, with thefollowing results.
The analysis of variance shows that there is a statistical effect of CHO on the Cooper Run Test when drunk by football players after anintensive two hour training session. Table 1 shows violation ofMauchly’s sphericity, where sphericity refers to the equality ofvariances of the differences between levels of the repeated measuresfactor, because the Sig value is below 0.05. Table 2 shows that withassumed sphericity, because the Sig value is below 0.05, there is asignificant difference between the conditions. We do not know, however,between which two conditions there is a significant difference. It maybe between one of three variables: between the placebo and 5% CHO,between 5% CHO and 10% CHO or between placebo and 10% CHO.
Our hypothesis, CHO has an effect on performance in the Cooper Run Test, has been confirmed. The null hypothesis, that no CHO has aneffect on performance in the Cooper Run Test, has been proven. Theresults show that the Cooper Run Test is performed better with fluidcarbohydrate.
Given that the mean distance run is greater for those runners having ingested CHO, it is of interest that the paired samples test shows a standard deviation lower between the 5% and 10% concentrations comparedto the placebo control. Statistically, these drinks are accuratemeasures of distance run, though the mean of 2380.33m, 2410.50m and2403.58m distance is descriptive of a positive effect.
We can only be certain that CHO has a positive effect on endurance, butthis research is inconclusive about the optimal levels of CHOconcentration in the fluid. Studies have shown that CHO in the form of glycogen present in the body before the start of exercise brings abouta greater endurance during athletic performance, therefore we must alsoqualify the discussion by saying that no participants in this studywere asked to specify their carbohydrate ingestion prior to thecommencement of the Cooper Run Test. Furthermore, each study participant had exercised strenuously during training before the measurements above were made, but this training was not necessarily the same for each meaning that, on the assumption that there might be differences in the way each footballer trained, we may be able to ascribe some effect on the results of post-training muscle glycogenlevels.
The concentration of CHO in the drinks taken by the football players is based primarily on the existing knowledge about the optimal level, asdiscussed in the literature review section, but not from the results isit possible that the level lies between 5% and 10%, unfortunately. Theplacebo containing no CHO allowed runners to run a longer mean distancethan the 10% drink. This is in line with previous research results.
Most earlier studies have allowed a four hour resting period prior totesting, however we considered three hours to be a better period, takenafter intensive football training. We also allowed for two days dietaryintake to be controlled, though how much this affected the test resultscan not be precise, but the training prior to testing was largelyfollowing previous research. The effect of the rest period is to allowthe level of glycogen in the muscle to stabilise. Perhaps because ofthe shorter period the glycogen levels were depressed and this may haveaffected the efficacy of carbohydrate uptake and therefore fed into ourresults. None of the participants suffered from hypoglycaemia.
There are lots of ways of carrying out a study similar to this. Thetwo most important methods were outlined in our literature reviewsection, namely focussing either on the type of carbohydrate used inthe test or focussing on the quantity of the ingested carbohydrate. Ofthe two, our study followed the second quantitative methodology withthree concentrations of 0%, 5% and 10% carbohydrate. Other types of carbohydrate could have been used, from a large possible selection,including glucose, sucrose, and fructose, amongst many others. Fructosehas been argued by previous studies (Dennis et al. 1997) to beundesirable as the source of carbohydrate intake. Glucose was used bymost studies (Wong et al. 1998, Wong et al. 2000, Bilzon et al. 2002,Fallowfield et al. 1993, Dennis et al. 1997) probably because itmatches the form of carbohydrate used by muscles during exercise mostclosely from a chemical point of view. Our focus on quantitativemeasurement of carbohydrate on the Cooper Run Test is based onscientific received wisdom, but this is not to say that future researchmight focus on a comparison between carbohydrates.
A carbohydrate is a mixture of carbon (C), hydrogen (H) and oxygen(0). Sugars, starches, cellulose are all examples of common carbohydrates. There are three main classes of carbohydrates, monosaccharides, disaccharides and polysaccharides. Examples of each ofthese are fructose and glucose; lactose, maltose and sucrose;cellulose, dextrin, glycogen and starch. The body manufactures glycogenmore easily from the monosaccharides, especially glucose; thereforethis is likely why glucose is deemed the best form of carbohydrate forathletic functioning.
The Cooper Run Test is a widely used sub maximal running test. It hasits origins in the work of Cooper (Cooper 1968) who reported a highcorrelation between VO2 and the distance run in 12 minutes. All our participants scored well on the test, compared to the generalpopulation, confirming their selection. Football training prior to theexercise must have harmed their recovery and affected their performanceon the Cooper Run Test.
There are many other measurements that could have been taken, howeverthese measurements were non-invasive and did not require a sophisticated laboratory style set up. Examples of invasive measures from previous studies include blood samples (Wong et al. 1998, Wong etal. 2000) and serum insulin sampling. With our study, the measurement of distance and time sufficed to give results consistent with our focuson the effects of CHO on football player’s performance.
It is worth considering the exercise that the participants undertookprior to the Cooper Run Test. The intensive football training on theground lasted for two hours and glycogen storage in the muscles were depleted by this. The carbohydrate ingested by those participants thatwere not given the placebo, remembering of course that the participants were not aware of the solution because of the double-blind conditions,was related to body weight; however the fluid ingested in each case was1 litre, or 1kg. Other studies did not measure the effect of fluid onits own since it assumed in the scientific literature that water does not have an effect on performance, which is dubious, but neverthelessthis study followed the literature. Perhaps for this reason the resultsfrom the study largely act as confirmation of the hypothesis.
The type of athletic activity might have repercussions for CHO effect.For example, many previous studies have measured cycling, which is adifferent type of activity using different muscles from running,specifically the abdominal section is not used as much in cycling. Itis possible that because the abdominal muscles are closer to thedigestive system that the ingested carbohydrates are more quickly usedby runners than cyclists.
In future studies there are a number of activities which might act asproper alternatives to football training. In fact, football training isitself a highly varied activity involving running, kicking, andstretching. We can not be certain from this study that the participantsall completed the same training. These would involve an equal number ofmen and women, all of whom could be assessed on their performance by alist of performance indicators, such as VO2 and endurance.
The fact that this study involved only men is supported by previousresearch, including the research discussed above in our literaturereview, all of which had a greater number of male participants. In thefuture it would be desirable to measure the performance, after CHOingestion, of men and women. It is not suggested that there might beany difference between the two; however it would be interesting tomeasure, especially if the activity were sexual intercourse.
Finally, the issue of recovery and what it involves in terms of lossof scientific conditions, such as in this study where lack ofmonitoring led to a key loss of control over subjects’ activity.Attempts at familiarisation were an attempt to address this issue,however because the trundle wheel could not be used simultaneously, therecovery was not uniform. Familiarisation was an essential part of ourstudy.
We neglected to record any of the manufacturers names of the equipmentused in our study. Any future study conducted must include as muchinformation about the experimental conditions as possible, includingany branding of materials; and also branding of the carbohydratesolution. This question relates to the economic importance of suchstudy. The literature review section revealed the presence of brandnames in the market for carbohydrate drinks, including Gatorade andLucozade, therefore the inclusion of equipment manufacturers’ brandingmust follow on the same principle.
The market for sports drinks is large and diverse, but a major benefitof our study is that it does not act as an advertising tool for aparticular product and therefore there is no question of ethicalconflict between the commercialisation of a drink and honest scientificreporting of its effects. We do not suggest that the reports frombodies such as the Gatorade Sports Science Institute are false; howeversuch open support of one carbohydrate drink should be against properscientific procedure, because science is not about profit. In our studythe carbohydrate was not made known to the study participants who were ignorant of the fluid they drunk. Science ought to be objective and impartial to the events it discusses.
Unfortunately this study does not reveal anything new about the effect of CHO on performance of the Cooper Run Test. It does tell ussomething positive, however, because football players are no exceptionto the correlation between athletic performance and carbohydrate ingestion. The Cooper Run Test has certain assumptions relating to the oxidation of carbohydrate to release energy in the muscle. Therefore our primary conclusion is that carbohydrate improves muscle performanceand because muscles are used by football players during running, they run for a greater distance having ingested carbohydrate. Energy is anecessary part of the equation as glycogen is used by muscles.
The storage of glycogen is significant as a factor which enablesfootball players to run for a longer distance. Our football players ranfor an above average distance therefore their fitness is above average,but their storage of glycogen was not included as an experimentalvariable, therefore we suggest that in a future study more attentionmust be paid to the diet.
Another improvement to this study could be to have more studyparticipants. Although twelve participants was near the average numberof participants of previous studies, the more participants the greaterprobability the mean effect of CHO is proven, as a direct relation. Onthe other hand, factors such as organising large numbers of footballplayers to run the Cooper Run Test might be practically prohibitive; however research in this area is cumulative. More research is certainly needed about the effect of CHO on football players – and other athletes.
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