Written by Astrid Naranjo (Clean Health Accredited Clinical Dietitian)
Water, like oxygen, is essential for life. Besides, water also performs several other important roles in the human body, including:
- Maintaining blood volume
- Transporting glucose and oxygen into your muscles.
- Serving as a critical component of your brain, blood, muscles, and bones.
- Aiding digestion of food, helping to convert it to energy you can use.
- Removing metabolic by-products like carbon dioxide from your hard-working muscles.
- Regulating body temperature, especially during your workouts when your muscles generate 20 times more heat energy than a body at rest.
- Allowing muscle contractions to take place.
Even with all of its benefits, drinking water and staying hydrated is one of the most overlooked components in fitness more than in actual sports. There is evidence that more than 40 percent of regular gym-goers are already partially dehydrated during their workouts (1). However, it is important to differentiate the role of hydration for performance versus health as well as how it differs between recreational athletes & gym goers vs elite athletes & sports.
Dehydration can have a significant effect on performance. Water losses via skin can range anywhere from 0.3 litres per hour during sedentary conditions all the way up to two litres per hour during high intensity activity (3,4). Anyone, from runners to lifters can become dehydrated if fluid loss is greater than fluid intake. It’s as simple as that.
Dehydration can lead to reduced performance, headaches, fatigue, and muscle cramps(2). At high level performance, hydration becomes even more important. Research suggests that optimum hydration in this population is not just about ‘drinking plenty’ and hoping for the best, it actually requires a good deal more thought and planning.
What is dehydration and how does it occur?
Dehydration occurs when more water and fluids leave the body than enter it. During exercise, the main way the body maintains optimal body temperature is by sweating. Heat is removed from the body when drips of sweat on the skin evaporate, resulting in a loss of body fluid. Sweat production, and hence fluid loss, increases with a rise in ambient temperature and humidity, as well as with an increase in exercise intensity.
Drinking fluid during exercise is necessary to replace fluids lost in sweat. This action will reduce the risk of heat stress, maintain normal muscle function, and prevent performance decreases due to dehydration (5). In most cases during exercise, the rates of sweat loss are higher than the rate people can drink, and this is especially true amongst athletes who can easily get into fluid deficit.
However, it is also important to acknowledge that it is possible to over-drink during exercise, specially if the rate of fluid loss is lesser than fluid intake and the rate of sweat loss is lower. (4-6). For example, drinking more fluid than is comfortable in conditions such as cool weather or when the exercise pace/intensity is gentle. Drinking too much fluid can be unnecessary and potentially dangerous, which during exercise, this over-hydration can cause a dilution of blood sodium levels (hyponatraemia). Symptoms include headaches, disorientation, coma, and in severe cases, death (10).
- Individuals more at risk of dehydration include athletes, people at higher altitudes, and older adults.
- The causes of dehydration include diarrhea, vomiting, and sweating.
- Early symptoms of dehydration include dry mouth, lethargy, and dizziness.
- Dehydration of greater than 2% loss of body weight can compromise physiological function and performance, as well as increase the risk of nausea, vomiting, diarrhoea, and other gastro-intestinal problems during exercise.
- It is impossible to ‘train’ or ‘toughen’ your body to handle dehydration.
- Over-hydration can also be a problem (although much less common than dehydration).
- Some recent evidence suggests that the 2% dehydration threshold may be relevant for sportsmen and women participating in sports where complex motor skills are important.
- Running or performing other types of exercise while in state of dehydration may cause an unfavourable shift in the hormone balance, by producing a more catabolic environment compared to full hydration (catabolism is something that most athletes try to minimise)(8,10,11).
What is the best fluid to drink?
- For most people, drinking plain water will meet their needs. Plain water alone is an effective drink for fluid replacement, especially in low intensity and short duration sports. If water’s too boring for you, try adding some fruit or other flavouring to keep your palette satisfied.
- Sports drinks (added carbohydrate and electrolytes) can enhance performance, especially in high intensity and endurance sports (and more importantly those over 90min of duration) (12). The better it tastes the more likelihood for athletes to consume more of it, which may assist in meeting fluid targets during competition or rehydrating more effectively.
- Carbohydrate in fluid provides a muscle energy source as well as enhancing flavour. Electrolytes such as sodium in fluid improves fluid intake as it stimulates the thirst mechanism, promotes both carbohydrate and water uptake in the intestines, and reduces the volume of urine produced post-exercise (4-7, 12). Of course, salt can be consumed in foods that are eaten at the same time as post-exercise fluids.
How much water should your client drink per day?
The DRI (dietary reference intake) for water is 2.7 L for women and 3.7 L for men per day. This includes water from all beverages (except alcohol) and liquid in food.
So, this estimate means that 80% of your water comes from fluid, the rest from food. This is where the 8 cups for women and 10-12 cups for men per day originated. It’s important to note that these recommendations are based on the ‘median intake of generally healthy people’ (6,10). Though athletes are certainly considered generally healthy, sweat losses can greatly increase these needs.As a rule of thumb daily water intake should be approximately 1 ml per calorie consumed, not including additional water losses through exercise (3).
Another guideline that can be useful for athletes, according to the National Athletic Trainers’ Association position statement, they should consume 500-600 millilitres of water 2-3 hours before exercise, then continue drinking 200-300 millilitres every 10-20 minutes before and during exercise. Athletes competing in events lasting more than 90 minutes should also consume a solution consisting of rapidly digestible carbohydrates and electrolytes (9,10,12)
For most people, the average gym goer, drinking plain water will meet their daily needs. For shorter bouts of exercise, electrolytes and carbs can be replaced at your next meal, but for longer exercise periods, they’re needed quicker, so sport drinks can be handy here.
How can your client tell if they’re drinking enough fluids?
One easy test is to recommend your clients to check their urine colour and aim for it to be clear—or very pale yellow not just before exercise but also throughout the day.
If you would like to learn more about the importance of hydration and how to optimize water intake in your clients, click here to enrol into the Performance Nutrition Coach Certification Collection!
- Stover, E. A., Petrie, H. J., Passe, D., Horswill, C. A., Murray, B., & Wildman, R. (2006). Urine specific gravity in exercisers prior to physical training. Applied Physiology, Nutrition, and Metabolism, 31(3), 320-327.
- Davis, J. K., Laurent, C. M., Allen, K. E., Green, J. M., Stolworthy, N. I., Welch, T. R., & Nevett, M. E. (2015). Influence of Dehydration on Intermittent Sprint Performance. Journal of Strength and Conditioning Research, 29(9), 2586-2593.
- Popkin BM, D’Anci KE, Rosenberg IH. Water, Hydration and Health. Nutrition Reviews. 2010;68(8):439-458.
- McArdle WD, Katch FI, and Katch VL. Sports & Exercise Nutrition, 4th ed. Baltimore, MD: Lippincott Williams & Wilkins, 2012.
- Kraft, J. A., Green, J. M., Bishop, P. A., Richardson, M. T., Neggers, Y. H., & Leeper, J. D. (2010). Impact of dehydration on a full body resistance exercise protocol. European Journal of Applied Physiology, 109(2), 259-267.
- Rosenbloom C. Sports Nutrition: A Practice Manual for Professionals. 6th ed. Chicago, IL: SCAN Dietetics Practice Group, Academy of Nutrition and Dietetics; 2017.
- Van Rosendal, S. P., Osborne, M. A., Fassett, R. G., & Coombes, J. S. (2010). Guidelines for glycerol use in hyperhydration and rehydration associated with exercise. Sports Medicine, 40(2), 113-139.
- Savoie, F. A., Kenefick, R. W., Ely, B. R., Cheuvront, S. N., & Goulet, E. D. (2015). Effect of Hypohydration on Muscle Endurance, Strength, Anaerobic Power and Capacity and Vertical Jumping Ability: A Meta-Analysis. Sports Medicine, 45(8), 1207-1227.
- Casa DJ, Armstrong LE, Hillman SK, et al. National Athletic Trainers’ Association Position Statement: Fluid Replacement for Athletes. Journal of Athletic Training. 2000;35(2):212-224.
- Clark N. Sports Nutrition Guidebook. 4th Ed. Champaign, IL: Human Kinetics, 2008.
- Judelson, D. A., Maresh, C. M., Farrell, M. J., Yamamoto, L. M., Armstrong, L. E., Kraemer, W. J., … & Anderson, J. M. (2007). Effect of hydration state on strength, power, and resistance exercise performance. Medicine and Science in Sports and Exercise, 39(10), 1817.
- Sawka MN, Burke L, Eichner R, Maughan RJ, Montain SJ, Stachenfeld N. American College of Sports Medicine. Exercise and fluid replacement position stand. Medicine and Science in Sports and Exercise. 2007; 377-390.