Carbs and exercise performance -
The screening of the full text of the remaining articles yielded 17 articles that were included in this review. These articles described 22 carbohydrate interventions covering test durations from 26 to min mostly cycling.
Thus, when considering only studies with a setting mimicking real-life competition, there is a mixed general picture about the ergogenic effect of carbohydrates ingested in the proximity of or during a performance bout with an unlikely effect with bouts up to perhaps 70 min and a possible but not compelling ergogenic effect with performance durations longer than about 70 min.
Peer Review reports. Carbohydrates are one of the two main fuels for sport activities, and their relevance for optimal sport performance is undisputed among experts [ 1 ]. Athletes not only ingest carbohydrates as general contributors to their daily energy need but also specifically as ergogenic agents in a more time-specific way, such as during a sport event or in the days preceding it.
This potential ergogenic effect of carbohydrates has been the subject of numerous investigations, and a series of reviews have summarized their outcome e.
In general, there is a consensus claiming an ergogenic effect of carbohydrates ingested just before or during a performance bout. One of the fundaments of science is the continuing questioning of current theories in order to corroborate them or, in the case of contradicting new evidence, to challenge them.
In the case of the ergogenic effect of carbohydrates ingested near to a performance bout, one could question if the study designs used to investigate this effect were suitable for extrapolating their outcomes to a real-life situation, particularly as a standardized, controlled laboratory setting can be quite different from the conditions of a real-life situation.
Subjects often fast overnight in performance studies. The reason for this is probably that the metabolism in fasted subjects is in a more balanced state, which might be more easily reproduced than a postprandial state.
However, the recommendation to athletes is not to compete in a fasted state because of potentially reduced liver glycogen stores and a subsequent negative effect on performance [ 3 ]. While this concern might be unsubstantiated overnight-fasted well-trained subjects can have more than twofold higher liver glycogen levels compared to overnight-fasted non-athletes, ca.
This is also does not reflect the real-life situation as usually a sporting event, at least in elite sports, requires performing either as fast as possible for a given distance e.
See Currell and Jeukendrup for a discussion on the different types of performance tests [ 6 ]. In two recent meta-analyses, the ergogenic effect of carbohydrates ingested during endurance sport activities was investigated with the inclusion of fasted subjects [ 7 , 8 ].
In our study, we also aimed at systematically reviewing the influence of carbohydrate intake on performance, but as we wanted to focus on the real-life applicability of the study outcome, we defined a priori to exclude studies with subjects who were fasted and in which the performance test was of a time-to-exhaustion character.
However, it was not the focus of this review to discuss why carbohydrate ingestion in the proximity of a performance bout may or may not help athletes.
We defined the protocol for conducting the systematic search before commencing the data search and we did not modify it thereafter.
One of us PCC then screened the PubMed for studies with a carbohydrate intake during the days prior to a sport performance, i. We originally planned to conduct a series of meta-analyses but abandoned this idea when it became clear that the number of studies fulfilling our inclusion criteria was small and the study designs were too heterogeneous for a meaningful grouping.
The plural of several terms was included as we realized that using only the singular of that term yielded a different number of hits although using the singular of a term should actually also identify abstracts including only the plural of a term.
We discarded articles with sufficient information in the abstract that clearly identified the study as ineligible, without consulting the full-text of the article. For the remaining articles, we checked the full-text for the information needed to evaluate the study. We additionally consulted the list of articles judged as eligible for the two meta-analyses mentioned above [ 7 , 8 ].
We included studies with a randomized, crossover, placebo-controlled, and if possible blinded study design. Blinding was not feasible as an absolute criterion, as sometimes the intervention could not be fully masked e.
no carboloading. The performance test had to be either of a time trial TT character, i. We excluded studies with time-to-exhaustion tests assessing the exercise capacity and discarded all studies without sufficient methodological information to enable a check of the inclusion criteria.
We combined the interventions according to sport type and physiological impact of the activity in particular with respect to endogenous energy delivery. no carboloading, ingestion of carbohydrate containing drinks vs. drinks containing no carbohydrates. The PubMed search yielded 16, articles and the abstract of 16, articles contained sufficient information to identify the corresponding study as not eligible.
The full text of the remaining articles allowed the identification of 16 articles that fulfilled the inclusion criteria. We identified one additional eligible article [ 9 ] through a scan of the reference lists of both meta-analyses of the similar topic [ 7 , 8 ].
Overall, the 17 articles comprised 22 interventions 14 articles with one intervention, one article with two interventions, and two articles with three interventions, Figure 1. Intervention type, performance bout and outcome of eligible studies. Two studies were carboloading interventions; in one study the drink was not ingested mouth-rinse study , and in the remainder 19 interventions, the effect of a carbohydrate-containing drink was compared to a non-carbohydrate placebo.
Cycling was the exercise mode used with two exceptions: one study with a soccer-specific mode and one study with a running exercise mode. Overall, a maximum of three studies had a comparable design same code in Figure 1. The subjects were men with one exception where both men and women served as subjects.
The performance was not significantly different with the following interventions: Both carboloading interventions, the only mouth-rinse intervention, the only running mode intervention, the only cycle TT carbohydrate vs. water intervention up to 60 min, and one of the two cycle TT carbohydrate vs.
water interventions between 61 to 90 min Figure 1. The main finding of this systematic review was that the study design used with the majority of studies investigating the ergogenic effect of carbohydrates ingested in the proximity of or during a performance bout was not suitable for extrapolating the performance outcome to a real-life situation.
Studies in which women served as subjects were non existing, except for one study where both genders made up the study population.
Systematic reviews of the scientific literature are considered a scientific and ethical imperative when developing policies and practical recommendations [ 28 ]. Nevertheless, systematic reviews are unfortunately not always an integral part of such processes.
The probably most prominent negative example was the World Health Organization, where "Systematic reviews and concise summaries of findings [were] rarely used for developing recommendations. Instead, processes usually [relied] heavily on experts…" [ 29 ].
Relying on experts when developing recommendations is a common procedure and not necessarily problematic. It only becomes a problem if the experts either do not use systematic approaches or do not properly describe the methodology used.
Regrettably, the latter often seems to be the case [ 30 ]. For example, during the process of performing this review we have encountered articles with missing information on the gender, age, exercise history, or regular training load of the subjects, lacking information on the blinding or randomization of the intervention, and missing information on a pre-exercise meal intake or on the amount of fluids ingested during the performance tests.
The omission of methodological information in systematic reviews is not the only issue with such analyses. However, no universal set of eligibility criteria exists, as the criteria must be fit for the specific purpose of the review.
According to our focus on the real-life portability of the performance outcome, we have used trained subjects exercising in a postprandial state and a performance test similar to a competitive event as main criteria.
These criteria have ultimately led to the exclusion of quite a number of studies, and one could argue that the criteria, therefore, were too restrictive. However, performing in a postprandial compared to a fasted state might indeed be two different things related to the potential ergogenic effect of carbohydrates.
In a sub-analysis of the meta-analysis by Temesi et al. Nevertheless, it indicates that the prandial state might influence a nutritional intervention, and therefore one should consider it with performance studies.
A second major aspect to consider when conducting a systematic review is the identification of possibly all studies fit for the purpose of the review [ 31 ]. A search across multiple databases seems by nature to be more promising in locating more relevant articles than restricting the search to one database only.
As we have only searched the PubMed, we may have missed a substantial number of relevant studies, which would have biased our results. The comparison with the studies identified for the meta-analysis by Temesi et al. The comparison with the meta-analysis by Vandenbogaerde and Hopkins [ 8 ], who used Google Scholar for their search, led to the additional identification of the same additional article already identified by the comparison of the meta-analysis by Temesi et al.
In contrast, we identified eight articles [ 10 — 14 , 19 , 21 , 25 ] that were not included in the meta-analysis by Temesi et al.
Overall, this indicates that in spite of searching only one database, we likely did not miss a substantial part of published studies on the topic under investigation. The current consensus indicates that carbohydrates ingested in the proximity of or during a performance bout are ergogenic.
However, the application of rigorous criteria to a systematic review, such as excluding fasted subjects and time-to-exhaustion test modes, led to a less convincing picture. We observed no significant performance improvement with most of the performance bouts lasting less than 70 min, and the results with longer performance bouts indicated a significant improvement with 10 of 17 interventions.
The absence of clear evidence is, nevertheless, not clear evidence of an absent effect. This is particularly true for the present review as we discarded many studies because relevant information was missing in the articles.
As mentioned above, we encountered studies among other with missing information on age, gender, prandial state, or VO 2max of the subjects, missing information on the blinding or randomization of the interventions, or missing information on the drink volume ingested during the intervention.
They showed no benefit in running a one-mile time trial or in sprinting performance in six meter sprints with either diet. But when athletes were on the high-carb diet, they showed wider swings of blood sugar glucose measured through continuous glucose monitoring than the low-carb diet, with nearly one-third of the athletes demonstrating levels consistent with prediabetes.
The first high-carb protocol was developed in the s when Swedish scientist, Gunvar Ahlborg, used new muscle-biopsy techniques to observe carb storage in the body. He found that athletes who consumed excess carbs stored the surplus of resulting glycogen the stored form of glucose in their muscles and liver.
He hypothesized that these glycogen stores created a bountiful source of fuel that would improve athletic performance. Later, he tested the idea on marathon runners, who reported being able to run longer after carbo-loading compared to moderate carb intake.
Since then, athletes have been trying to stuff their muscles with as much glycogen as possible before a performance. Scientists and exercise nutritionists hailed carbs as the superior nutrient among top athletes. Scientists also theorized that the body uses different nutrients for various levels of exercise.
During low-intensity activities, the body burns relatively more fat, but as intensity increases, the body switches over to relatively more carbs. But, as the popularity of low-carb diets has grown, so too have studies that challenge the idea that high-carb intake is better for athletic performance.
And according to Prins, few high-quality, randomized studies have compared the two diets head to head. He set out to change that. Prins was one of the scientists to test this theory. In , he and a team of scientists in the US and South Africa found that high- and low-carb diets result in equivalent outcomes in athletic performance.
In the study, published in the Journal of Sports Science Medicine , researchers prescribed a group of recreational runners a high-carb and low-fat diet for six weeks. Then, they measured their performance in a five-kilometer race.
After a short break in which they could eat whatever they wanted, researchers switched them to a low-carb and high-fat diet for an additional six weeks and had them run another race. When he compared the performance between the first and second races, carbo-loading had no benefit.
Prins said they controlled the experiment, so exercise and dietary intake were equivalent, meaning participants ate the same number of calories but in different distributions. After an adjustment period of about two weeks, athletes performed just as well on the low-carb versus high-carb regime.
With neither diet conferring much of a performance advantage, the researchers next looked for a health advantage. This time, in addition to measuring their athletic performance, researchers looked at body mass composition, metabolite oxidation rates using VO2 Max, insulin and glucose levels, as well as cardiometabolic markers like cholesterol and triglyceride levels.
Researchers evaluated how the athletes did in a one-mile time trial and a series of six meter sprints and found no difference in performance between the two diets.
Next, they measured fat and carb oxidation, t he rate at which the body uses each nutrient for energy. When athletes were following low-carb diets, they found some of the highest levels of fat-oxidation ever recorded in a study, according to Prins.
During exercise lasting more than 60 minutes, an intake of carbohydrate is required to top up blood glucose levels and delay fatigue. Current recommendations suggest 30 to 60 g of carbohydrate is sufficient, and can be in the form of lollies, sports gels, sports drinks, low-fat muesli and sports bars or sandwiches with white bread.
It is important to start your intake early in exercise and to consume regular amounts throughout the exercise period. It is also important to consume regular fluid during prolonged exercise to avoid dehydration.
Sports drinks, diluted fruit juice and water are suitable choices. For people exercising for more than 4 hours, up to 90 grams of carbohydrate per hour is recommended.
Carbohydrate foods and fluids should be consumed after exercise, particularly in the first one to 2 hours after exercise. While consuming sufficient total carbohydrate post-exercise is important, the type of carbohydrate source might also be important, particularly if a second training session or event will occur less than 8 hours later.
In these situations, athletes should choose carbohydrate sources with a high GI for example white bread, white rice, white potatoes in the first half hour or so after exercise.
This should be continued until the normal meal pattern resumes. Since most athletes develop a fluid deficit during exercise, replenishment of fluids post-exercise is also a very important consideration for optimal recovery.
It is recommended that athletes consume 1. Protein is an important part of a training diet and plays a key role in post-exercise recovery and repair.
Protein needs are generally met and often exceeded by most athletes who consume sufficient energy in their diet. The amount of protein recommended for sporting people is only slightly higher than that recommended for the general public.
For athletes interested in increasing lean mass or muscle protein synthesis, consumption of a high-quality protein source such as whey protein or milk containing around 20 to 25 g protein in close proximity to exercise for example, within the period immediately to 2 hours after exercise may be beneficial.
As a general approach to achieving optimal protein intakes, it is suggested to space out protein intake fairly evenly over the course of a day, for instance around 25 to 30 g protein every 3 to 5 hours, including as part of regular meals.
There is currently a lack of evidence to show that protein supplements directly improve athletic performance. Therefore, for most athletes, additional protein supplements are unlikely to improve sport performance.
A well-planned diet will meet your vitamin and mineral needs. Supplements will only be of any benefit if your diet is inadequate or you have a diagnosed deficiency, such as an iron or calcium deficiency. There is no evidence that extra doses of vitamins improve sporting performance.
Nutritional supplements can be found in pill, tablet, capsule, powder or liquid form, and cover a broad range of products including:.
Before using supplements, you should consider what else you can do to improve your sporting performance — diet, training and lifestyle changes are all more proven and cost effective ways to improve your performance.
Relatively few supplements that claim performance benefits are supported by sound scientific evidence. Use of vitamin and mineral supplements is also potentially dangerous.
Supplements should not be taken without the advice of a qualified health professional. The ethical use of sports supplements is a personal choice by athletes, and it remains controversial. If taking supplements, you are also at risk of committing an anti-doping rule violation no matter what level of sport you play.
Dehydration can impair athletic performance and, in extreme cases, may lead to collapse and even death. Drinking plenty of fluids before, during and after exercise is very important. Fluid intake is particularly important for events lasting more than 60 minutes, of high intensity or in warm conditions.
Water is a suitable drink, but sports drinks may be required, especially in endurance events or warm climates. Sports drinks contain some sodium, which helps absorption.
While insufficient hydration is a problem for many athletes, excess hydration may also be potentially dangerous. In rare cases, athletes might consume excessive amounts of fluids that dilute the blood too much, causing a low blood concentration of sodium.
Ecercise Journal Performamce 12Article number: 16 Cite this Physical activity. Metrics details. There Carbs and exercise performance a performmance claiming an ergogenic perfogmance of carbohydrates ingested in the Diabetic foot care products of or during a performance bout. However, in performance studies, the protocols that are used are often highly standardized e. fasted subjects, constant exercise intensity with time-to-exhaustion testsand do not necessarily reflect competitive real-life situations. Therefore, we aimed at systematically summarizing all studies with a setting mimicking the situation of a real-life competition e. Macronutrients are perforjance for athletic performance as well as general health. You have likely Physical activity about the importance of protein, especially exercisd it comes to Carbz Physical activity and improving Cognitive function improvement methods composition. But what about other Carbs and exercise performance, specifically carbohydrates and fats? How do these play into athletic performance? If you are not an athlete, but you are physically active, do protein, carbohydrates, and fats also play an important role? I have discussed the importance of protein and recommended intake for athletes and other recreationally active individuals in a previous article. It is likely you already know that protein rebuilds muscle but it has many other important functions.
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