The purpose of this investigation was to determine the effects of caffeine’s proposed ergogenic capabilities upon human sprint times and performance.
Twelve female sports students (20 ± 2 yr, 1.64 ± 0.05 m, 58.9 ± 3.9 kg) were utilized as the subjects for this investigation which was conducted in the Oxstalls Sport Hall, Gloucester, using the light gate equipment. All subjects were familiarized with the experimental design and apparatus before proceeding. The necessary forms were signed by the participants and personal information acquired. Subjects were administered either caffeine (5 mgˆ™kg-1 of body mass) or placebo, and ingested the substance 1 hour prior to testing in a single blind fashion. After a 5 minute warm up, 12 x 30 metre sprints were performed by each subject with a 30 second interval between each sprint. The experiment was repeated a week later using the same procedure but with the participants taking the opposite substance to the previous weeks test.
Subsequent to the interpretation of the data, fastest sprint time (s), mean sprint time (s), fatigue and RPE were obtained. All of which were examined statistically, the paired t-test was used as a test of significance, the mean as a measure of central tendency and standard deviation as a measure of reliability and variance. Fastest sprint times decreased from 5.34 ± 0.27 s to 5.27 ± 0.25 s when taking caffeine compared to placebo. Mean sprint times decreased slightly from 5.56 ± 0.29 s to 5.55 ± 0.29 s when consuming caffeine. RPE again showed a slight decrease from 14 ± 1 to 13 ± 1 using Borg’s (1982) 6-20 scale after caffeine ingestion. Using the fatigue index as recommended by Glaister et al. (2004), caffeine showed an increase (5.16 ± 1.91) compared to placebo (4.13 ± 1.51).
It was concluded that 5 mgˆ™kg-1 of body mass of caffeine did have a significant effect on fastest sprint time and RPE, and that fatigue was heightened when taking caffeine. Though it did not have any significant ergogenic effects on mean sprint times at the p<0.05 level upon sprinting performance in women.
Deliberate ingestion of caffeine within sport is the focus for this study. It is caffeine’s supposed ergogenic properties in relation to sporting performance which will be investigated.
Caffeine, also known chemically as trimethylxanthine, is one of the most common drugs in the world, with the benefit of having minimal health risks attached to taking it (Graham, 2001). It is among the most widely used drugs because of its ubiquitous occurrence in commonly consumed beverages such as coffee, tea and cola. Many drugs contain caffeine and are readily accessible to the public in the form of over the counter (OTC) stimulants and combination analgesics. Due to this accessibility and its social acceptance, caffeine plays a major part in the western diet, with over 80% of the adult population consuming the drug on a daily basis through various methods (Schwenk, 1997). With caffeine consumption being so common, its positive and negative effects are noticed so easily. The study will look into its potential positive ergogenic effects due to its ever increasing popularity in sporting performance.
Earlier studies by Pasman et al. (1995), Bell and McLellan (2002), Greer et al. (2000), Graham and Spriet (1995), regarding caffeine’s ergogenicity, are linked to effects upon endurance times rather than sprint performance. Increased endurance performance is supported by many of the studies, and rarely have they found to be no effect (Butts and Crowell, 1985) and (Falk et al., 1990). Due to it ergogenic properties, caffeine’s popularity has increased in sporting contexts.
This investigation is primarily concerned with attempting to assess caffeine’s effectiveness as an ergogenic aid in respect of its effects upon the anaerobic energy system, and its subsequent relevance to sprint times and fatigue in women. By implementing multiple sprint tests, this will provide the necessary data required for evaluating the anaerobic energy system, sprint times and fatigue.
Caffeine is a natural substance, which is utilized every day, whether it is in food, drink, medicine and more importantly for the purpose of this study, sport. It is caffeine’s ability to be used in a number of ways, which makes it an ever increasing drug in society. Applegate and Grivetti (1997) has claimed that caffeine has been used as a means of masking fatigue since the early 1900s, the use of this ergogenic aid became popular following widely publicized research indicating improved endurance performance. There may be other factors contributing to its increase in popularity over the years. For example, caffeine is seen as a socially acceptable drug in society, as mentioned earlier, its minimal health risks has made the substance generally recognized as safe (GRAS) according to the food and drug administration (FDA), meaning the intentional consumption of caffeine becomes less stigmatized. Another possible factor behind its popularity is the ever increasing demand for athletes to achieve and the pressure being placed upon them by themselves and outside sources. Such demands being placed on athletes at all levels, ranging from recreational to professional, will inevitably cause participants to seek out an advantage and give into the persuasion of the stimulants which is being forced upon them. Thus, leading to companies promoting and persuading athletes to use their products to achieve the best performance possible.
Due to the increasingly competitive arena in which athletes find themselves, the promotion of performance enhancing substances are surrounding them almost daily. The legality and use of ergogenic aids such as caffeine has caused many debates and varied opinions about its uses in competitive sport. There are currently three categories in which substances can be classed; legal, controlled and illegal. In 1967, the International Olympic Committee (IOC) banned all performance enhancing drugs (PED’s). The formation of the World Anti-Doping Agency (WADA) in 1999 took over the IOC’s responsibilities regarding PED’s. The World Anti-Doping Agency reviewed the banned substances list in 2004 and changed the legality of caffeine, allowing athletes to take the substance. Though the caffeine is defined as legal, WADA are still monitoring athletes in order to detect any patterns of misuse within the sport.
Caffeine’s positive ergogenic effects have been well documented in numerous sports, but caffeine consumption in sports like darts, archery and snooker can have a detrimental effect upon performance. The absorption of caffeine can lead to an increase in heart rate, restlessness, anxiety and hypertension, all of which could have a damaging effect upon sporting performance. However, in spite of some possible negative effects in a slight number of sports, caffeine’s popularity is ever increasing as a legal performance enhancer.
Manufacturers of sporting performance supplements have, through their market research, recognized the increasing popularity and attraction of using performance enhancing supplements. Companies have tapped into a bona fide consumer need for energy. As a result of this, the market place has been flooded with masses of supposedly ergogenic concoctions. The market for energy products has grown tremendously, leaping from a niche market for endurance athletes to mainstream customers. Many products take the form of drinks containing caffeine, Red Bull is still the leader in that category, with about 50% of the market share. Since the emergence of Red Bull many copycat drinks have been produced and marketed as a performance enhancer. These drinks contain excessive amounts of caffeine and have been promoted as an ergogenic aid, though in many countries, energy drinks have been banned due to its potential health risks, especially with regards to children. The problem with proving the ergogenic effects of drinks like these is the varying tolerance levels of each individual, which according to Kendler and Prescott (1999) can depend on many factors, including caffeine consumption patterns, age, body weight and physical condition. In spite of this, athletes will still consume the caffeine products in order to gain that advantage and improve performance without realising some of the negative effects, such as dehydration.
Extreme caffeine consumption can lead to possible side effects, which many consumers are oblivious too. Some of which are restlessness, diarrhoea, headaches, anxiety, insomnia, and in extreme circumstances, tachycardia or cardiac arrhythmia.
It is important to consume caffeine in moderation; those who ingest large amounts regularly and then try to decrease their intake by a substantial amount can cause problems for themselves. Caffeine withdrawal can lead to symptoms such as sleepiness, irritability, headaches and in rare circumstances, nausea and vomiting. Phillips-Buteand Lane (1997) has suggested that headaches caused by caffeine withdrawal are due to the appropriate mechanisms of the body becoming oversensitive to adenosine. Due to this, blood pressure will drop excessively and cause excess blood in the head, leading to a headache.
Still, with all the possible side effects of excessive consumption and withdrawal symptoms, caffeine’s popularity amongst the general public is unwavering. Companies are still promoting the benefits of caffeine without indulging in its flaws, particularly in the sporting sector, meaning its popularity raises even further.
This investigation is concerned with how performance in sport can be improved by increased sprint speed and a decrease in fatigue after caffeine ingestion. Improvements in an athlete’s speed over short distances is vital in many sports, as the intensity and the pace of games are increasing in the current era. Such improvements can help in field and court sports such as football, tennis and hockey to name a few. Having the ability to run that split second quicker than an opposing athlete may make a dramatic impact upon the sporting performance, and most importantly the result.
There has been a steady increase in the number of studies examining the effects of caffeine upon high intensity, short duration exercises, and more specifically, repeated sprints. This area is still up for investigation as caffeine’s ergogenic benefits are not so clear cut, as they are in endurance exercise. Many studies have produced results either supporting or diminishing any relationship between caffeine and repeated sprint performance, but each study varies on its reason behind such change. The study undertaken by Glaister et.al (2008) found results of that support a clear ergogenic effect of caffeine on repeated sprints but stated that further research is required to establish the mechanisms of this response. Papers by Glaister et.al (2008), Stuart et.al (2005), Paton et.al (2001) and Crowe et.al (2006) shall provide a solid base for research and literature regarding multiple sprints or high intensity short duration exercises.
The rationale of this study is to evaluate and research the available literature, and moreover to examine in larger detail the responsible functions and mechanisms within the body that manipulate and contribute to the possible enhancement of sprint performance following an ingested dose of caffeine.
The main purpose of this study is to conclude whether or not an administered dose of caffeine will improve sprint performance and to conclude whether caffeine is ergogenic in this specific subject area. The objective will be tested and achieved by firstly administering a certain dosage of caffeine subsequent to a pre test. Then after a certain period of absorption this will be followed by 12 x 30 metre sprints, which will hopefully provide the necessary results for the assessment of fastest and mean sprint times, followed by fatigue and RPE values. The methodology will be executed as efficiently and as accurately as possible, limiting the likelihood of any discrepancies creeping in and influencing the overall evaluation of results.
The outcome of this investigation is expected to be valuable to the sporting world, and especially to athletes that partake in sports associated with the demands of fast sprints, such as those mentioned earlier. It will provide the necessary knowledge and allow athletes to consider the option of indulging in the use of what is at present a legal stimulant, helping them to optimize their sporting performances.
2.1 -Previous Studies
The involvement of an all female participant group in this study means it opens up a new area of research. Previous research involving caffeine and exercise has always used a solely male or mixed sex sample. Bell and McLellan (2002) used 15 males and 6 females for their study, Crowe et al. (2006) also followed suit and used 12 males to only 5 females. More specifically, affects of caffeine in multiple sprint tests and short term high intensity exercises has provided an even more bias participant sample. A study by Paton et al. (2001) on the ‘effects of caffeine ingestion on repeated sprints in team-sport athletes’ used 16 male participants. The most important study being that of Glaister et al. (2008) into the supplementation of caffeine in multiple sprint running performances, this study looked at 21 male participants and excluded females all together. Many of these studies have used forms of exercise and equipment for testing that are available to women. This distinct lack of research on solely women participants regarding the effects of caffeine has created a chance to look into this trend and the possible reasons behind it.
WHY NOT SO MUCH ON WOMEN€”BIOLOGICAL DIFFERENCES BETWEEN SEXES AND CAFFEINES EFFECTS.
Biological differences between the 2 sexes may cause researchers to use mainly male participants. Although males and females are very much the same in build, there are some aspects that may vary and cause one of the sexes to act differently.A study by Farag et al. (2006) found that on the placebo session, men and women showed a significant BP increase to stress, although women had significant cardiac responses whereas men had vascular responses, therefore proving that males and females react differently to certain conditions.
DIFFERENCE OF EFFECTS OF CAFFEIENE.
WHY SPRINTING TEST
LIMITATIONS – MENSTRUAL CYCLE, CONTRACEPTIVE, PREVIOUS EXPERIENCE.
The liver needed for caffeine metabolism. In healthy adults, caffeine’s half-life is approximately 4.9 hours. In women taking oral contraceptives this is increased to 5-10 hours (Meyer et al., 1999) and in pregnant women the half-life is roughly 9-11 hours (Ortweiler et al., 1985).
2.2 – Mechanisms of Ergogenicity
Caffeine acts as an A1 and A2a adenosine receptor antagonist, regular consumption of caffeine is associated with an up regulation of the number of these adenosine receptors in the vascular and neural tissues of the brain (Fredholm et al, 1999). Caffeine is metabolized in the tolerance for it; regular users do however develop a strong tolerance to this effect (Maughan & Griffin, 2003). Studies by Armstrong et al (2007) have generally failed to support the common notion that ordinary consumption of caffeinated beverages contributes significantly to dehydration.
RELIABILITY OF MULTIPLE SPRINT TEST
The dosage from caffeine studies have ranged from 1-15mgˆ™kg-1. The optimal dose has not been determined because it may vary according to the sensitivity of the individual to caffeine. However, Cadarette et al. (1982) found doses between 3and 6mgˆ™kg-1 produce an equivalent ergogenic effect to higher doses, and this has led Graham et al. (2000) to suggest that the optimal dose thus lies in this lower range. Using the findings established by others, participants will be administered 5mgˆ™kg-1 for the purpose of this research.
Time After Ingestion
Recent research from Bell and McLellan (2002) found that only exercise times 1and 3hours after drug ingestion were significantly greater than the respective placebo trials of 23.3±6.5,23.2±7.1,and 23.5±5.7min. For this research, the multiple sprints will take part 35 minutes after ingestion of the caffeine tablet, due to practical and time implications. Even though caffeine has a half-life of 4-6 hours, this implies that high levels of caffeine will be in the blood for up to 3-4 hours after ingestion, most studies have focused on exercise performance 1 hour after ingestion. Bonati et al. (1982) made the assumption that the ergogenic effect is related to the circulating level of the drug in the blood. Thus maximal effects are assumed to occur 1 hour after ingestion, when peak blood concentrations are observed. Studies by Nehlig and Derby (1994) suggested that waiting 3hours may be more optimal because the caffeine-induced effect on lipolysis is greater than at earlier times after ingestion. However, the hypothesis that the ergogenic effect from caffeine is due to an enhanced free fatty acid mobilization and tissue utilization has not found much support in the recent literature.
Using 24 well trained cyclists, Hogervorst et al. (2008) established that not only does a bar containing 100mg of caffeine have an impact on physiological endurance performance but also a complex cognitive ability during and after exercise. Crowe et al. (2006) conducted a similar test involving cycling and found both positive and negative results from the caffeine/placebo supplementation. Plasma caffeine concentrations significantly increased after caffeine ingestion; however, there were no positive effects on cognitive or blood parameters except a significant decrease in plasma potassium concentrations at rest. Potentially negative effects of caffeine included significantly higher blood lactate compared to control and significantly slower time to peak power in exercise bout 2 compared to control and placebo. Caffeine had no significant effect on peak power, work output, RPE, or peak heart rate.
On Short Sprints
There have been many studies that have looked at the effects of caffeine on short sprints or short duration high intensity exercises, which recreate in game scenarios from team sports. A study by Stuart et al (2005) on rugby players showed that caffeine is likely to produce substantial enhancement of several aspects of high-intensity team-sport performance. The effects of caffeine on mean performance (±90% confidence limits) on sprint speeds were, 0.5% (±1.7%) through 2.9% (±1.3%), showing a stong positive correlation regarding sprint speeds. The study involved straight line sprints but also consisted of tests to measure passing accuracy, agility and power. A more specific study by Glaister et al (2008) focused on the effects of caffeine on multiple sprints, this involved 12 x 30 metre sprints with 35 second intervals. Relative to placebo, caffeine supplementation resulted in a 0.06-s (1.4%) reduction in fastest sprint time (95% likely range = 0.04-0.09 s), which corresponded with a 1.2% increase in fatigue (95% likely range = 0.3-2.2%). The study found that caffeine has ergogenic properties with the potential to benefit performance in both single and multiple sprint sports, although the effect of recovery duration on caffeine-induced responses to multiple sprint work requires further investigation. In contrast, Paton et al (2001) had a similar study design but the observed effect of caffeine ingestion on mean sprint performance and fatigue over 10 sprints was negligible. The true effect on mean performance could be small at most, although the true effects on fatigue and on the performance of individuals could be somewhat larger.
The aim of this study is to examine the effects of caffeine on mean sprint times (s), fastest sprint times (s), RPE and fatigue from 30m multiple sprints. By using female participants this develops a new area of research as previous research is focused solely on male or mixed participants.
2.3 – Resulting Hypotheses
After reviewing the literature, hypotheses were formulated for the purpose of this study.
H0 – There will be no significant difference in fastest sprint times following the consumption of 5 mgˆ™kg-1 of caffeine as compared to the non caffeine condition.
Ha – There will be a significant difference in fastest sprint times following the consumption of 5 mgˆ™kg-1 of caffeine as compared to the non caffeine condition.
H0 – There will be no significant difference in mean sprint times following the consumption of 5 mgˆ™kg-1 of caffeine as compared to the non caffeine condition.
Ha – There will be a significant difference in mean sprint times following the consumption of 5 mgˆ™kg-1 of caffeine as compared to the non caffeine condition.
H0 – There will be no significant difference in rate of perceived exertion (RPE) following the consumption of 5 mgˆ™kg-1 of caffeine, compared to the non caffeine condition.
Ha – There will be a significant difference in rate of perceived exertion (RPE) following the consumption of 5 mgˆ™kg-1 of caffeine, compared to the non caffeine condition.
H0 – There will be no significant difference in fatigue following the consumption of 5 mgˆ™kg-1 of caffeine compared to the non caffeine condition.
Ha – There will be a significant difference in fatigue following the consumption of 5 mgˆ™kg-1 of caffeine compared to the non caffeine condition.
3.1 – Subjects
Twelve female subjects (20 ± 2 yr, 1.64 ± 0.05 m, 58.9 ± 3.9 kg) from the University of Gloucestershire volunteered to take part in this investigation which was conducted in the Sports Hall at the Oxstalls Campus.All subjects participated in a multiple sprint sport on a regular basis. They played one of tennis, badminton, squash, football, hockey, rugby and lacrosse for the university and at a moderate standard so therefore were considered to have a sound level of baseline fitness. Participants from these teams trained at least once a week and were also involved in a match once a week.
Before proceeding with the test, all of the subjects were informed of the testing procedure and how the data was going to be used in this study. Participants were given a list, outlining suitable kit to wear for the tests. Questionnaires were handed out to the participants to find out how many hours a week they participated in sport and their daily caffeine consumption levels. Before commencing, the participants filled out a health questionnaire to enable participation and signed an informed consent form. The subjects were advised to maintain their normal diet over the duration of the last two experimental runs, and were advised not to drink or eat 1 hour before testing. It was also important not to consume any caffeine, alcohol or any other stimulant products from a list provided to them, at least 24 hours before each experimental test and not to perform any strenuous exercise 24 hours prior to testing. Any subjects not being able to comply with the guidelines were eliminated from the test.
3.2 – Experimental Procedures
All the participants undertook 3 multiple sprint tests in total, 1 familiarization test to get use to the experiment and outline any problems and then the latter 2 will were the repeated measures experimental tests. These tests consisted of 12 x 30m straight sprints and were repeated at 30 second intervals. Light gates (Brower Timing Light Gate System) were set up at either end of the 30m track to record times. Regarding the last two trials they were conducted single blinded so that results could be compared between the two groups. All the trials were run at approximately the same time of day and spaced a couple of days apart. Personal information from each participant including age, height (SC126 wall mounted Stadiometer : Holtain Limited, Crymych, Dyfed), and body mass (Seca 888 electronic personal scale : seca gmbh and co Ltd, Medizinsche Waggen und Messsysteme), were collected at the familiarization test too, ready for the experimental tests. After the final test, participants were asked if they could identify the difference between the placebo and caffeine and to express their reasons for this. The testing was performed in a controlled environment, using an indoor sports hall with a hard solid ground with inbuilt shock pads under the surface. Data being collected was average speed (ms-1), RPE, fatigue and fastest and slowest sprint times (s). All equipment was calibrated prior to testing.
3.3 – Pre-Test
On the day of each experimental run, participants were administered either the placebo or caffeine 1 hour before the testing is due to start in order for the affect of caffeine to be absorbed into their system. The caffeine dosage administered was 5 mgˆ™kg-1 of body mass; rounding to the nearest 50mg. 10 minutes before each multiple sprint test participants undertook a standardized warm up which lasted for approximately 5 minutes. It included a 400 metre jog at their own pace, a series of sprint drills incorporating high knees, heel flicks and walking lunges to replicate the test and some practice sprints. Five minutes before the test, participants performed some stretches and gave themselves some time to get ready physically and mentally.
3.4 – Testing
In order to prevent false triggering with the light gates, participants started 1 m behind the line. The gates were set up at the start line and 30m along on the finish line. After the sprint, the subjects stayed down the same end as they finished in order to maximise recovery time between sprints, this lasted for 30 seconds. The countdown for each sprint was performed manually and will last 5 seconds. Each participant was verbally encouraged by others in order for them to try and work at their maximal effort.
3.5 – Data Collection and Statistical Analysis
With regards to the reliability of multiple sprints testing, it has previously been established by Glaister et al (2007) that high degrees of test-retest reliability can be obtained in many multiple sprint running indices without the need for prior familiarization. However, for this experiment, the familiarization test helped the researcher get use to the testing procedures to allow smother running on the experimental runs. Average speed (ms-1) for each participant was calculated using the timing gates, along with this, fastest and slowest sprint times were recorded too. Each participant was asked their rating of perceived exertion (RPE) after every sprint using Borg’s (1982) 6-20 scale. The last component being measured was the effects of caffeine on fatigue from the multiple sprints, by using the percentage decrement calculation as used by Glaister et al (2004):
Fatigue = (100 x (total sprint time/ideal sprint time)) – 100
The total sprint time is the sum of all the sprints by the participant, divided by the ideal time, which is the time of the fastest sprint multiplied by how many sprints that were performed. Multiply the answer by 100 and then subtract 100 and you get the fatigue index of the individual.
Data will be analysed using SPSS (Statistical Package for the Social Sciences) for Windows. This way comparison between the two data sets can be made. The test used was a repeated measures dependant t-test, with a 95% confidence level. This is used when there is only one sample that has been tested twice (repeated measures). If the calculated statistical significance (95% confidence level), then the null hypothesis (H0) which states that the two groups do not differ is rejected in favour of the hypothesis, which states that the groups do differ and that there is an effect.
3.6 – Facilities and Equipment
Gaining access to facilities and equipment will need to be addressed in advance so that equipment isn’t already booked out and that the facility is booked early enough so that it gives enough time to analyse results and write up the final proposal before the submission deadline. As the test was undertaken in the University Sports hall it was easier to book out than that of a public hall. The hall was booked out through phoning the university sports office and organising a time suitable for both needs. For the purpose of the study a wall mounted stadiometer, stopwatch, scales, placebo, light gates, a computer with a statistical analysis program and caffeine tablets were acquired.
3.7 – Budget
All costs were identified before the study was undertaken. None of the participants were paid for their participation. The hall was booked out for three 1 hour slots equating to £60 (£20 per hour), due to the affiliation with the University the hall was free of charge but if it was to be booked by a member of the public, these costs would need to be included. The cost of the caffeine was £10 for ninety 200mg tablets, and the placebo pills cost £3 per 50.
3.8 – Ethical Considerations
The participants received a voluntary informed consent form, which outlined the procedure, how the data was collected and how the data was used and by who. The data will be kept private under the Data Protection Act 1998 and data can’t be linked to an individual participant. All participants were above the age of 18 so that they can give their own consent, also they were participating voluntarily. A health questionnaire was administered to find out any potential health risks, along with a list stating the possible effects of caffeine. Once all this information was given, participants were given the chance to refrain from participating. Participants were told that placebo was given instead of caffeine to half the population and not to the other half. There is a sense of deception due to the participants not knowing if they are taking the caffeine or the placebo, but there is no medical risk and if told it can affect the results of the study.
3.9 – Temporal Plan
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