Why do we need to hydrate correctly?
Here we present a precautionary tale of salt and water. We all understand we need to drink to stay alive and we have to maintain the correct fluid levels in our bodies to perform well as athletes; few understand why. This post might just help you to understand variations in how you felt when exercising and provide answers that can help you become more a more competent athlete because of a greater understanding of hydration.
Why do we need to hydrate correctly?
Ross Johnston 5/10/2018
The hydration-sodium balance explained in basic terms and why it is so important for athletes to understand – or the hydration debate as I see it from an athlete’s perspective. Just a couple of big words to negotiate but they really are important to your ongoing health and sporting performances.
Hyponatremia
Hyponatremia refers to an abnormally low (diluted) sodium concentration in your blood and can be caused by drinking too much water. Sodium is a key regulator of the amount of water surrounding cells in your body so if your sodium levels become diluted by a rise in your body’s water level there is a consequent swelling of your cells. Such swelling can cause many health problems, some of which can be life threatening if not recognized and treated quickly.
Hypernatremia
In contrast, hypernatremia (or dehydration) refers to an abnormally high concentration of sodium in the blood. Usually hypernatremia is mild and is not life threatening, however it is important to address the problem to return bodily functions to normal.
Discussion
Clearly these are potentially serious and very pertinent issues for those of us that live and/or train in hot conditions. They provide a clear incentive to ensure that you understand the importance of maintaining a correct hydration/sodium balance before, during and after exercise and it is not as simple as drinking lots of water and swallowing salt tablets or relying on sports drinks to maintain that balance for you.
Athletes who consume a well-balanced diet and only exercise for relatively short durations probably won’t have to worry about blood-sodium levels and only remain conscious of maintaining a suitable water intake. Those that undertake longer sessions may need to supplement sodium intake and here electrolyte drinks can be beneficial (but be aware of how much sugar you could be consuming – sugar-free alternatives make it easier to monitor your nutritional intake).
The hydration message coming from the marathon and ultra running science is to err on the side of under- rather than over-hydration. This approach is less likely to see you end up under medical supervision (hyponatremia, or over-hydration, is more dangerous and more difficult to treat than hypernatremia, or under-hydration). What does this mean for athletes? Simple – drink a little and often but only drink-to-thirst (D-2-T), do not drink to inflexible pre-determined schedules and/or large volumes.
If your nutritional plan for longer exercise or race plans is sound it will include sufficient electrolyte in one form or another to maintain blood-sodium balance. Sodium is a major component of electrolyte supplements – but always check labels to be sure you are consuming what you expect. It should be relatively simple to maintain blood-sodium balance within appropriate limits when following the D-2-T hydration strategy. To assist in this you should familiarize yourself with the signs and symptoms of hypo- and hyper-natremia.
Signs and symptoms
Hyponatremia(overhydration) |
Hypernatremia(underhydration) |
|
|
|
|
Bibliography
Agrawal V, Agarwal M, Shashank R, Joshi A, Ghosh K (2008) Hyponatremia and hypernatremia: Disorders of water balance. J Assoc Physicians India 56:956–964
Arnaud MJ, Noakes TD (2011) Should humans be encouraged to drink water to excess. Eur J Clin Nutr
Buono MJ, Ball KD, Kolkhorst FW (2007) Sodium ion concentration vs. sweat rate relationship in humans. J Appl Physiol 103:990–994
Cheuvront SN, Kenefick RW, Montain SJ, Sawka MN (2010) Mechanisms of aerobic performance impairment with heat stress and dehydration. J Appl Physiol
Hew-Butler T, Weisz K (2016) Hypernatremia. Clin Lab Sci
Felig P, Johnson C, Levitt M, Cunningham J, Keefe F, Boglioli B (1982) Hypernatremia Induced by Maximal Exercise. JAMA J Am Med Assoc
Krabak BJ, Lipman GS, Waite BL, Rundell SD (2017) Exercise-Associated Hyponatremia, Hypernatremia, and Hydration Status in Multistage Ultramarathons. Wilderness Environ Med
Martinez-Cano JP, Cortes-Castillo V, Martinez-Villa J, Ramos JC, Uribe JP (2018) Dysnatremia among runners in a half marathon performed under warm and humid conditions. BMJ Open Sport Exerc Med
Maughan RJ, Shirreffs SM, Watson P (2007) Exercise, Heat, Hydration and the Brain. J Am Coll Nutr
Montain SJ, Sawka MN, Wenger CB (2001) Hyponatremia associated with exercise: Risk factors and pathogenesis. Exerc Sport Sci Rev
Noakes TD (2013) Hyponatremia of Exercise. In: Sports Nutrition.
O’Connor RE (2006) Exercise-induced hyponatremia: Causes, risks, prevention, and management. Cleve Clin J Med
Page AJ, Reid SA, Speedy DB, Mulligan GP, Thompson J (2007) Exercise-associated hyponatremia, renal function, and nonsteroidal antiinflammatory drug use in an ultraendurance mountain run. Clin J Sport Med
Rogers IR, Hew-Butler T (2009) Exercise-associated hyponatremia: Overzealous fluid consumption. Wilderness Environ Med
Rosner MH (2009) Exercise-Associated Hyponatremia. Semin Nephrol 29:271–281
Rosner MH, Bennett B, Hew-Butler T, Hoffman MD (2013) Exercise-associated hyponatremia. Hyponatremia Eval Treat:175–192
Rosner MH, Bennett B, Hew-Butler T, Hoffman MD (2013) Exercise-associated hyponatremia. In: Hyponatremia: Evaluation and Treatment.
Speedy DB, Noakes TD, Schneider C (2001) Exercise-associated hyponatremia: A review. Emerg Med