Determining body hydration -
Purpose: Understanding the importance of euhydration in humans in order to ensure good health in various situations, the purpose of this review is to examine the available techniques in assessing hydration status.
Recent findings: During the past 20 years, many indices have been developed to assess hydration levels accurately in humans. Changes in body weight, haematological and urine parameters, bioelectrical impedance, skinfold thickness, heart rate and blood pressure changes are among these indices.
Using this method assumes that all mass lost during exercise is only due to sweat, but many other factors can contribute towards mass loss Some of these include:. However, it is important to understand the different variables that can affect the reliability of the results.
Urinary Indices Hydration status can be measured by monitoring characteristics such as volume, colour conductance and osmolality 6. Under normal conditions, the amount of urinary volume excreted can range from 1.
When exercise commences, water conservation mechanisms are activated in the kidneys to ensure that both plasma volume and intracellular water are maintained, this has an effect on the aforementioned urinary characteristics.
how much the athlete has urinated that day requires a large amount of compliance and cooperation from the athlete; however, a more qualitative method can be used, such as asking the athlete the frequency of urination during the day 6.
Both approaches require a degree of athlete education to ensure that the data collected is accurate. Measuring urine osmolality involves the collection of urine and using a freezing point osmometer to determine the number of solutes e.
NaCl per kg of solution 6. This requires a trained technician and also expensive equipment, though there is an alternative. The use of a Sparta 5 Conductance Metre has been validated in previous research A 6-point Likert Scale can be used to estimate hydration status through urinary colour Copies of the scale can be distributed between athletes.
This is non-invasive, non-expensive and simple to use, however, the athlete must be educated to ensure that they use to scale correctly and must take note of the results. These methods to estimate hydration status through urinary indices may prove invalid if there are large acute ingestions of fluid after exercise 30, This may produce diluted urine and mask their true hydration status 6.
Methods must be put in place to ensure that hydration testing is completed as soon as possible after exercise so that the data collected is as accurate and precise as possible.
Blood Indices It is thought that a number of blood-borne indices can be used to test the dehydration status of an athlete. Hypertonic dehydration e. from profuse sweating can be detected through changes in plasma osmolality and plasma sodium 30, 32 , whilst hypotonic or isotonic dehydration can be detected through serial haematocrit or haemoglobin measurements This method requires a properly trained professional to ensure that safe and sterile measurements are taken with the appropriate laboratory equipment.
Examples of which are outlined below:. This method of hydration testing can be costly, invasive and labour-intensive 6. Due to the fact that it requires blood sampling, there will always be a risk of infection, bruising and vein damage.
From this study, they concluded that urinary measures may be more accurate during conditions of mild dehydration; which other research supports This could be due to the fact that urine is more concentrated to maintain normal blood chemistry during exercise 6. Plasma sodium has been found to increase under conditions of dehydration This study aimed to investigate the use of plasma sodium as a marker of dehydration during exercise in heat.
It involved 2 hours of cycling 3. Results show an increase in plasma sodium from baseline measurements, and an extra 20 minutes of cycling 1. One study compared haematocrit and haemoglobin levels to levels of total body water both before and after an exercise intervention lasting 14 days It showed that blood indices correlated with total body water throughout the study, suggesting that these may be useful for situations of hypotonic and isotonic dehydration.
Whilst plasma osmolality, blood sodium, haematocrit and haemoglobin may provide accurate information regarding hydration status, the limitations outlined earlier seem to outweigh the benefits at this point in time.
Further research and engineering are needed to provide a more practical approach when using these measurements. Limitations regarding hydration testing primarily appear to be related to its practicality in the field.
For example, it would be impractical to have an entire AFL or Rugby League team use BIA after every training session or to use USG to estimate hydration level. BW changes , measurement accuracy will, most likely, be sacrificed. Coaches, fitness and medical staff must communicate what they feel is the most appropriate method for their particular sport.
A further issue with hydration testing can be the priority that this measurement takes in the eyes of the fitness and medical staff.
Coaches outside of an elite environment may not have the time or resources to hydration test their athletes, potentially putting their performance and health at risk.
Future research in the area of hydration testing should focus on determining if current methods can be altered so that they can provide an even more valid and reliable measurement as well as addressing the following issues:. Hydration testing is a very important part of any athletic programme and can prevent serious performance and health deficiencies.
There are methods available which are valid, inexpensive and non-time-consuming, but the confounding variables that may affect results must be addressed.
Future research is required to assess whether urinary and blood indices can be used as hydration tests in a practical sense. William is a recent graduate from Deakin University with a Bachelor of Exercise and Sport Science.
He has just completed a year-long internship with The Geelong Football Club an elite AFL club in where he was exposed to GPS and HR analytics as well as other aspects of high performance. This free poster is for you to put up on the walls of your gym, changing rooms, etc.
to remind your athletes to stay properly hydrated. Learn from a world-class coach how you can improve your athletes' agility. This course also includes a practical coaching guide to help you to design and deliver your own fun and engaging agility sessions. Our mission is to improve the performance of athletes and teams around the world by simplifying sports science and making it practical.
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Contents of Article Summary Why is hydration important for athletes? What is hydration testing? Why is hydration testing important? How is hydration measured? Are there any issues with hydration testing? Is future research needed with hydration testing?
Conclusion References About the Author. References Sawka, MN and Young, AJ. Physiological Systems and Their Responses to Conditions of Heat and Cold. Burke, LM. Eichner, ER. Maughan, RJ. Montain, SL and Stachfield, NS. American College of Sports Medicine position stand: Exercise and Fluid Replacement.
Medicine and Science in Sports and Exercise 39 : , Clarkson, PM and Roberts, WO. American College of Sports Medicine roundtable on hydration and physical activity: consensus statements.
Current Sports Medicine Reports 4 : , Washington D. Dietary Reference Intakes for Water, Sodium, Chloride, Potassium and Sulfate. National Academy Press. Sawka MN and Pandolf KB. Effects of body water loss on physiological function and exercise performance. Perspectives in Exercise Science and Sports Medicine 3 , Opplinger, RA and Bartok, C.
Hydration Testing of Athletes. Sports Medicine 32 : , Exercise Physiology [Textbook], Cheuvront, SN. Carter III, R and Sawka, MN. Fluid balance and endurance exercise performance.
Current Sports Medicine Reports 3 : , Koulmann, N. Barraud, PS. Raphel, C. Jimenez, C and Merlin, B. Influence of variations in body hydration on cognitive function: effect of hyperhydration, heat stress, and exercise-induced dehydration.
Journal of Psychophysiology 14 —36, Physical Exercise and Exhaustion from Heat Strain. Journal of the Korean Society of Living Environment System 8 : , Branch, JD. Leutholtz, BC and Swain, DE. Effects of dehydration and rehydration on the one-repetition maxmimum bench press of weight trained males.
Dehydration is more likely in a warmer climate or hot weather. A person should always make sure to drink extra fluids in the heat. Similarly, exercise can cause dehydration because the body uses more fluid and loses water through sweat.
Older adults may gradually lose some of their sense of thirst. A good rule of thumb is to drink fluids throughout the day. Once a person feels thirsty, they may already be slightly dehydrated. Water toxicity happens when there is too much water in the body.
This can dilute essential electrolytes in the blood, cause cells to swell, and put pressure on the brain. Drinking too much water is difficult. There have been cases of water poisoning in people who drank a lot of water in a very short space of time.
This may be during endurance sports because of heat stress, or when using recreational drugs that increase thirst. There is no clear limit for drinking too much water.
The kidneys can remove 20—28 liters of water per day, but they cannot excrete more than 0. Drinking more than this can be harmful. Click here to learn more about water intoxication.
A majority of the human body consists of water. A person can maintain the balance of water in the body by taking in enough fluids during the day.
Water is crucial to keep the body working correctly. It is present in the blood, skin, organs, and bones.
There is water in every cell of the body, from the brain to the teeth. Find out more about how much fluid the body needs every day, how the body balances its fluid, and more. Drinking too much water can lead to water intoxication, which can be fatal.
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With the hot weather upon us in the northern hemisphere, this marks a time for many to get Determiining and Deterkining the warm Ignite fat burning, but caution should always be exercised Morphological training adaptations the potential risks for hyrdation. Before discussing effective hydrstion by which we Morphological training adaptations monitor hydration, take a brief moment to reflect upon the existing strategies you utilize to verify hydration for yourself and your clients as a Nutrition Professional. Do you rely upon the sensation of thirst as your guide, daily weight fluctuations or perhaps urine color to monitor fluid needs? Considering how the sensation of thirst generally kicks in only when the body reaches about one percent dehydration i. It does not provide much of a buffer for individuals exercising in the heat who may be susceptible to compromised performance. The NHS hyxration drinking at least six to eight Determining body hydration Determininh fluid per day, but Determiming people are drinking a lot less. Morphological training adaptations Chitosan research and studies the NHS, a Dstermining deficiency can make you tired, dizzy or lightheaded — and it can also affect your skin elasticity. To check whether you are drinking enough water, a simple skin test can check your body hydration — and it is backed by the National Library of Medicine. Hold for a few seconds and then let go. If the skin bounces back immediately, you are hydrated.
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