The Effects Of Hydration On Endurance Exercise Performance

7 Aug

(This is a research paper I wrote in grad school.  It is a good read, but it is very long… If you are an endurance athlete I highly suggest you read the entire post.)

The Effects Of Hydration On Endurance Exercise Performance

Hydration is a key element to sport and exercise performance.  In order for the body to function at a high level, hydration status is very important.  Much research has been compiled on the effects of hydration status on endurance exercise performance.  It is evident that maintaining hydration status is crucial during endurance exercise and sporting events.  If an athlete does not stay well hydrated, or over hydrates, their performance can be negatively affected. Dehydration of more than two percent can decrease aerobic exercise performance (Clark, & Lucett, 2010).  Measurements of core temperature, heart rate, and perceived exertion all demonstrate the physiological effects dehydration has on the body (Clark, & Lucett, 2010).  This extra physiological stress negatively affects the body’s ability to perform at a high level.  When body water content is decreased there is an increase in heart rate as well as a decrease in stroke volume, indicating an increase in cardiovascular strain (Sherreffs, 2005).  While dehydrated, the same exercise task is perceived as requiring more effort than if it was performed in a well-hydrated state (Clark, & Lucett, 2010).  This perception can have negative effects on the athlete’s metal capacities during their athletic events.  Various cognitive tasks such as visuomotor tracking, short-term memory, response time, coordination, attention, and mental focus are all consequences that can be attributed to dehydration (Clark, & Lucett, 2010).  With only a 2% loss of bodily mass due to de-hydration, endurance exercise performance can be greatly affected in a negative manner.

Research Question:
How does hydration status affect endurance exercise performance?
Data Sources:

Articles were chosen based upon researching hydration and endurance exercise.  The research articles that contained studies about the effects of caffeine and creatine were excluded due to their possible effects on performance and hydration.  To keep up with current research, only articles published after the year 2000 were included.  In order to ensure quality of information, only peer-reviewed articles were selected.  Search terms included: hydration, fluid, dehydration, performance, endurance, exercise, and fatigue.  Full text articles were found through MEDLINE, SPORTDiscus, and Academic Search Complete.

Annotated Bibliography:
1. Knechtle, B., Kiouplidis, K., Knechtle, P., Kohler, G., Imoberdorf, R., & Ballmer, P. (2010). Does a multi-stage ultra-endurance run cause de- or hyper hydration?. Journal of Human Sport & Exercise, 5(1), 59-70.

The authors from this study are from various hospitals and clinics in Switzerland.  The intended audience would be for those in academia who wish to learn what effects an ultra endurance race might have upon hydration status.  The study followed one woman through an ultra endurance race that covered multiple stages to find the effects the event had upon human body composition and hydration status.  The study found that after the event the subject had lost 0.3kg of fat mass and 1.2kg of skeletal muscle mass.  Throughout the event total body water increased and after each stage the subject appeared to be dehydrated according to the administered tests, however; by the end of the race the athlete appeared to be hyper hydrated rather than dehydrated.  This study is important because it shows the exact opposite results as to what is expected after a multi-stage endurance event.  This study plants the seed that a de-hydrated and hyper hydrated state can both negatively affect endurance exercise performance.

2. Cheuvront, S., Montain, S., & Sawka, M. (2007). Fluid replacement and performance during the marathon. Sports Med, 37(4-5), 353-357.

The authors of this paper are from the US Army Research Institute of Environmental Medicine in Natick, Massachusetts.  The intended audience for this review is the fitness professionals helping individuals prepare for a marathon as well as the individual participant themselves.  This review lays out a strategy for replacing fluids to optimize marathon performance.  The article states that endurance exercise performance can become impaired when dehydration exceeds 2% of body weight.  It is suggested that endurance athletes competing in marathons should consume 0.5-1.0L of water/hour in order to stave off dehydration of more than two percent of body mass.  The demands of marathon running can require substantial heat loss in the form of sweat evaporation; therefore it is important to replace this fluid. The authors recommend that runners drink enough fluids to prevent a greater than 2% loss of body mass, thus preserving performance. The authors also recommend that the drinking rates should never result in weight gain.  This study carries great weight because it begins to delve into the importance that proper hydration has upon keeping the body’s core temperature within normal limits during endurance exercise.

3. Judelson, D., Maresh, C., Anderson, J., Armstrong, L., Casa, D., Kraemer, W., & Volek, J. (2007). Hydration and muscular performance; does fluid balance affect strength, power, and high intensity endurance?. Sports Med,37(10), 907-921.

The authors of this review article are associated with the Human Performance laboratory at the University of Connecticut as well as The Department of Kinesiology at the California State University at Fullerton.  The intended audience of this review is the exercise professional looking to learn more about effects of hydration on performance.  The review article suggests hypo hydration, a decrease in total body water, limits strength, power and high-intensity endurance.  This is an important factor to consider when an athlete is trying to maximize performance.  This paper is quick to point out that previous studies on the effects of hydration status on performance have failed to control variables such as heat stress and factors that skew the association between hydration state and performance, such as caloric restriction and training status.  The review ultimately finds that high intensity endurance is effected by hypo hydration more that strength and power.  This research relates to the current topic because it finds a clear difference in what types of activities are affected by hydration status.  It shows that endurance activities are more greatly affected by the status of one’s hydration than that of strength and power exercises.  This leads one to believe that the longer and exercise event takes place, the greater effect hydration status has upon the exercisers performance.

4. Casa, D., Stearns, R., Lopez, R., Ganio, M., McDermott, B., Yeargin, S., Yamamotto, L., & Mazerolle, S., Roti, M., Armstrong, L., Maresh, C. (2010). Influence of hydration on physiological function and performance during trail running in the heat. Journal of Athletic Training, 45(2), 147-156.

The authors are associated with: the University of Connecticut, Indiana State University, Westfield State College, Texas Health Resources Presbyterian Hospital, and the University of Tennessee.  The intended audience would be for those in academia who are looking to better understand how hydration affects performance in a setting outside the laboratory.  The study aims to examine the effects of moderate water deficit on the physiological responses to various exercise intensities in a warm outdoor climate.  The researchers suggest that due to dehydration there is increased strain placed upon the cardiovascular system, increased heart rate and a decrease in stroke volume, which hampers performance.  Subjects from this study participated in a trail running event and the researchers examined the changes in body mass, core body temperature, sweat rate, heart rate, performance, and perceptual responses.  These variables were study through several trails where the subjects ran a race trial hydrated and the same race dehydrated.  The study concludes that when dehydrated the athletes had higher core temperatures and heart rates. During the trials the subjects reported the same level of perceived exertion in the hydrated and dehydrated races, yet each participant finished the race slower when dehydrated.  This is an important study as it directly relates a decrease in performance to hydration status and directly states the mechanisms to which the negative attributes are related.

5. Edwards, A., & Noakes, T. (2009). Dehydration: Cause of fatigue or sign of pacing in elite soccer?. Sports Med, 39(1), 1-13.

The authors of this opinion paper are associated with the Faculty of Health Sciences in Palmerston North, New Zealand, Carnegie Research Institute, Leeds, UK, and the Department of Human Biology at the University of Cape Town in South Africa.  This article is intended for the sports professional that is interested in learning more about the effects of dehydration on performance.  The article laments that dehydration is known to be negatively associated with endurance-based performance and looks to see if it affects soccer performance.  The study suggests that consciously perceived factors, that are negative, such as thirst, may lead to limitations in performance.  This perception of increased effort can have negative effects on an athlete and possibly impair performance.  Ultimately the article concludes that dehydration in itself cannot be the only limiting factor that affects performance in soccer.  However, throughout the article the authors state the negative influences dehydration has on the body as well as what systems are affected.  This article is important because it points out that a drop in performance due to dehydration can be related to a reduced mental capacity and not that just of a physiological entity.  This means that dehydration can negatively affect an athlete in more than one aspect of his/her performance.

6. Merry, T., Ainslie, P., & Cotter, J. (2010). Effects of aerobic fitness on hypohydration-induced physiological strain and exercise impairment. Acta Physiologica,198, 179-190.

The authors of this study are associated with the School of Physical Education and the Department of Physiology at the University of Otago, Dunedin, New Zealand.  The intended audiences of this study are the athletic trainers, strength coaches, and fitness professionals that need to be informed of the negative effects of hypo hydration on their athletes.  The study aims to observe the effects of being hypo hydrated versus euhydrated during endurance exercise in trained and untrained males.  The researchers observed how aerobic fitness modulates induced-induced effects on physiological strain.  It is interesting to note that when in a hypo hydrated state the only the untrained subjects had an increase in heart rate and core temperature during the exercise test, but when compared with the trained subjects the findings were not statistically significant.  Ultimately the research concludes that performance decrements are visible due to hypo hydration, however; it seems as though high aerobic fitness lessens the negative effects of hypo hydration during exercise at intensities relative to exercise training.  The researchers also conclude that although induced impairs performance, it is not yet exactly known but that in involves a combination of physiological and psychophysical factors that may limit muscle activity.  This study examines how fitness level relates to performance decrements when hypo or euhydrated.  This is important because it shows being under hydrated as well as over hydrated can both negatively affect performance.

7. Knicker, A., Renshaw, I., Oldham, A., & Cairns, S. (2011). Interactive processes link the multiple symptoms of fatigue in sport competition. Sports Med,41(4), 307-328.

The authors of this review article are associated with the German Sport University Cologne, Institute for Movement and Neurosciences in Cologne, Germany, School of Exercise and Sport Science, Faculty of Health Science, Queensland University of Technology in Brisbane, Queensland, Australia, and School of Sport and Recreation, Faculty of Health and Environmental Sciences, AUT University in Auckland, New Zealand.  The information within this review paper is intended for those in academia who are interested in learning the many causes of fatigue.  The aim of this review article is to gather information about fatigue and its many mechanisms.  The findings of this review state dehydration sometimes causes a deterioration of motor skill as well as a higher rate of perceived exertion.  This review points out the negative effects dehydration has on the mental aspects of fitness.  Performance can also be limited by the mental capabilities of an athlete, not just physical mechanisms.

8. Aragon-Vargus, L., Moncada-Jimenez, J., Hernandez-Elizando, J., Monge-Alvarado, M., & Barrenechea, A. (2009). Evaluation of pre-game hydration status, heat stress, and fluid balance during professional soccer competition in the heat. European Journal of Sport Science, 9(5), 269-276.

The authors of this study are associated with the School of Physical Education and Sports at the University of Costa Rica in San Jose, Costa Rica, the University of Granada in Granada, Spain, and the University of Medical Sciences Andres Vesalio Guzman in San Jose, Costa Rica.  The intended audiences for this study are the athletic trainers, strength coaches, and fitness professionals that need to be informed about the hydration status of their athletes.  This study monitored 17 male soccer players during a game and assessed initial measures of hydration status, fluid balance, and core temperature changes at the before and after a professional soccer game.  Many of the players were found to be dehydrated after the game; this was compounded by an initial status of induced.  Many variables can contribute to dehydration during a game: pre-event hydration status, environmental conditions, training intensity, clothing, inadequate fluid intake, and sweat rates.   The study states that coming into an event in a dehydrated state can have clear negative consequences on performance, as shown by Armstrong, Costill, & Fink, in a study they completed in 1985.  The importance of the study is to suggest a proper hydration strategy well in advance of an athletic event in order to avoid starting exercise in a dehydrated state, thus having negative effects on performance.  The paper suggests that tasks with a large aerobic component are affected to a greater extent than those that do not.  This article reinforces what was found in an earlier study in that endurance exercise is more greatly affected than strength & power output.

9. Maughan, R. (2003). Impact of mild dehydration on wellness and on exercise performance. European Journal of Clinical Nutrition,57(2), S19-S23.

The author is part of the School of Sports and Exercise Sciences at the Loughborough University in Loughborough, UK.  The intended audience of this article is that of the general population who is interested in learning more about how dehydration affects exercise performance.  As it relates to exercise performance the report makes comments on findings from Adolf et al. (1947) that athletes do not report the sensation of thirst until they have lost two percent of their body mass in water.  The article also states that blood flow to the skin is reduced when dehydration of about 2% occurs, thus making it more difficult for the body to reduce its core temperature.  This article is important to research because it directly states how performance is affected by dehydration.  Cooling the body is a basic need to function properly.  If this cannot be achieved efficiently performance will be hampered.

10. Tarnopolosky, M., Gibala, M., Jeukendrup, A., & Phillips, S. (2005). Nutritional needs of elite endurance athletes. part i: Carbohydrate and fluid requirements. European Journal of Sport Science, 5(1), 3-14.

The authors are associated with the Department of Pediatrics and the Department of Kinesiology at the McMaster University in Hamilton, Canada, and the School of Sport and Exercise Science at the University of Birmingham in Edgbaston, Birmingham, Canada.  The intended audiences of this article are the athletes who participate in endurance events and the fitness professionals charged with preparing these athletes for their events.  This article looks into the effects and recommendations for carbohydrate and fluid consumption for endurance athletes.  It states that a loss of body water can result in decreased performance through a reduction in plasma volume, stroke volume, as well as blood flow to the skin.  It also states that a reduction in performance is possibly due to a decrease in blood flow to the muscles.  The article also states that Walsh et al. (1994) found that a 1-2% loss of body water resulted in reduction of endurance capacity by 44%.  Tarnopolosky and his collaborators suggest consuming 400-600mL of fluid two hours prior to exercise, 100mL every ten minutes during exercise, and to replace the amount of fluid and electrolyte losses after exercise.  The review makes note that consuming a beverage that contains electrolytes and glucose is better for rehydrating versus water alone.  Guidelines for proper hydration are needed for both the general population as well as for those who train athletes.  Knowing how much fluid is necessary to stave off dehydration can help limit its effects on performance.

11. Sherreffs, S. (2005). The importance of good hydration for work and exercise performance. Nutrition Review, 2, S14-S21.

The author is from the School of Sport and Exercise Sciences at Loughborough University in Loughborough, United Kingdom.  The intended audience for this article is anyone looking to gain basic knowledge on hydration at its most basic level.  Through her review Sherreffs finds that dehydration of 2-7% can cause a decrease in endurance exercise performance but the extent of that decrease ranges from 7-60%.  She also finds that a 1-2% dehydrated status only impaired performance when endurance exercise lasted longer than 90 minutes.  In the article Sherreffs states that decrements in performance are due to an increase in cardiovascular strain, increased heat strain, altered central nervous function, altered metabolic function, or any combination of the aforementioned.  As dehydration increases subjects to report feelings of headache, tiredness, reduced levels of alertness, and greater difficulty concentrating which can greatly reduce the will to continue exercise.  In the open discussion portion of the paper a debate about climate conditions is brought up and all agree that endurance exercise performance in the heat is more greatly affected by dehydration than in less harsh environments.  As stated in this research we see specific measures of to what degree dehydration can negatively impact performance.  It is shown that it can have a great effect on many processes of the body.

12. Constant, J. (2010). Water as an essential nutrient: the physiological basis of hydration. European Journal of Clinical Nutrition, 64, 115-123.

The authors of this article are associated with the Department of Physiology at the University of Lausanne in Pully, Switzerland and Nestle´ Waters, Paris, France.  The intended audiences of this review are the fitness professionals who need to understand the physiological effects hydration has upon the human body.  As the review begins the authors explain that water is an essential nutrient and is present in all of our cells, tissues, and organs, therefore the balance of it within our body is crucial.  Because water has a large heat capacity it limits drastic changes in body temperature, which could ultimately affect exercise performance.  When the body sweats it dissipates heat in a very efficient manner.  When the body’s hydration status is negatively balanced sweating becomes lessened and therefore core temperature can rise.  This would then negatively impact an exercisers performance.  Optimal functioning of the human body requires a good hydration level.  This article relates to the current research topic by stating the importance of water within the body.  As every cell contains water; the status of proper hydration becomes crucial when taking in considerations for proper function of the cooling system of the body.  This article is important to research because it explains the vast role water plays in our system.  In order to understand how performance is affected by hydration status we must first understand the role fluid plays in our body to ultimately learn how it may negatively impact exercise performance.

13. Kratz, A., Siegel, A., Verbalis, J., Adner, M., Shirey, T., Lee-Lewandrowski, E., & Lewandrowski, K. (2005). Sodium status of collapsed marathon runners. Arch Pathol Lab Med,129, 227-230.

The authors of this study hold either a PhD or are an MD associated with various hospitals and universities in and around the Boston, Massachusetts area.  The intended audiences of the study are those who participate in marathons and the fitness professionals who help these athletes prepare for such events.  The study examines 140 runners who took part in the Boston Athletic Association Marathon in 2003 and collapsed during or shortly after the race.  The study found that the collapsed runners were either over hydrated or de-hydrated.  This study is important for research purposes because it shows that a swing of hydration status too much in one direction, positive or negative, can have adverse effects on performance.

14. Maughan, R., & Sherreffs, S. (2010). Development of hydration strategies to optimize performance for athletes in high-intensity sports and in sports with repeated intense efforts. Scandinavian Journal of Medicine & Science in Sport , 20(2), 59-69.

The authors of this article are from the School of Sport and Exercise Sciences at Loughborough University in Loughborough, United Kingdom.  The intended audience of this review article is anyone that is looking to gain more knowledge on proper hydration strategies to prepare for a sporting event.  Several of the studies reviewed for this article found a 4-27% reduction in peak aerobic power due to hypo hydration of 1-8%.  Through their review of various studies Maughan and Sherreffs found hypo hydration of 1-5% will impair physical and mental performance.  Because hydration status is so important for proper performance, athletes need to be educated on how to remain hydrated before, during, and after exercise events.  This study is important because it directly correlates dehydration with a decrement in performance.

Clinical Implications:

The knowledge obtained from this literature review will yield guidelines for current and future hydration strategies as well as information on how to assess hydration status.  Endurance athletes and general exercisers alike need to be informed of proper hydration strategies, and the information contained within this review is sufficient enough in order to begin the education of hydration status for these populations.  Athletes and the general population alike must be given proper knowledge on staying proficiently hydrated.


The metabolic demands of endurance exercise can result in substantial sweat losses and levels of dehydration consistent with compromised endurance performance.  A loss of body water constituting 2% of the exerciser’s body mass is enough to negatively effect physical and mental performance during endurance exercise.  Water is present in every cell of our body and is imperative for proper functioning.  Any deviation in hydration status too far from the norm, whether positive or negative, can impair endurance exercise performance.  It is evident that maintaining hydration status is crucial during endurance exercise and sporting events.

Future Research:

Future research should look to examine the magnitude to which endurance exercise performance is impaired.  It is also imperative to study mechanisms by which performance is impaired.  It is generally understood that dehydration is mostly due to loss of fluid from sweating while exercising and future research should look at the impact the climate has upon hydration status.

Clark, C., & Lucett, S. (2010). Nasm’s essentials of sports performance training. (First ed., p. 409). Baltimore, MD: Wolters Kluwer Lippincott Williams & Wilkins.

Sherreffs, S. (2005). The importance of good hydration for work and exercise performance. Nutrition Review, 2, S14-S21.


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