We hope that everyone is enjoying the slow transition of weather as the days start to become a little warmer and the days are a little bit longer. And as the days get warmer, it is very important to refill on water and electrolytes – especially if you are planning on training outside. But how much is too much? How much is too little? Well keep reading to find out!
First it is very important to define a few terms: First is euhydration which is when the body has an adequate volume of water to meet physiological demands. Hyperhydration is when there is an excess amount of water in the body. Hypohydration is when there is an insufficient volume of water in the body. Lastly, dehydration is the process of losing body water and transitioning from a state of euhydration to hypohydration.
Also it is important to understand that there is water that is constantly changing in its concentration between intracellular (ICF, fluid in the cells) and extracellular (ECF, fluid outside the cells) fluids. This concept will be important in understanding electrolytes and how to keep the concentration relatively consistent.
Next let’s distinguish between cations and anions. Cations are positively charged ions (major one being Sodium [Na+]) and anions are negatively charged ions (Chloride [Cl-] and Bicarbonate HCO3-]). For the most part, Potassium [K+] is the main cation in the ICF with a small concentration of [Na+]. But this is the opposite in the ECF. Now because these concentrations are different, through the principles of osmosis, [Na+] is constantly leaking into cells while [K+] is leaking out. But never fear, the pumps in our cell membranes are working hard to maintain healthy concentrations.
Now this is where things get interesting for the athletes. Normally, the level of water is is pretty evenly distributed between the ICF and the ECF, BUT a large amount of water is lost during strenuous exercise which means water within the cells shrink (water moves from ICF to ECF) to balance the concentration. Conversely if there is a drastically large amount of water in the plasma in the ECF, then water shifts into the cells and they begin to swell. It is important to note here a condition known as hyponatremia where a large amount of water is quickly consumed and the body is unable to excrete it quickly enough through the renal system.
The average adult male has about 2.8L of plasma. A loss of 10-20% over prolonged exercise drastically reduces exercise performance. The average marathon runner or elite level soccer player have a typical sweat rate in excess of 2.5L/hr. During prolonged exercise, the body is unable to match fluid loss with intake and absorption (The body simply cannot do it fast enough). Also, the sodium content of sweat ranges from 10 to 70 mEq/L with the average being 35mEq/L (Sawka et al., 2007). 1 mEq of sodium is equal to 23mg of sodium. With these numbers in mind the average athlete may lose up to 1,610 mg of sodium per liter. Exercise lasting 1 to 2 hours doesn’t generally pose a problem for the athlete and so their main concern should primarily water loss. Anything more and they have to take electrolyte ingestion into account. As we venture past the 2 hour mark, carbohydrate intake and sodium intake start to play a role.
A simple and cost effective method in measuring fluid loss during your workout can come in two methods. The first is the urine color chart (pictured above). The lighter your urine, the more hydrated you are. The drawback to this is of course its susceptible to subjective interpretation and also diet heavily influences the color of urine as well. The second method is calculating over the course of a workout your total water loss. 1 litre of water weights approximately 1 kg or 2.2lbs. For example, a marathoner records his weight at 145lbs before he goes for a 1 hour basebuilding run at a steady pace. He weighs himself after the hour run and logs in at 142.8lbs. The runner can then calculate the rate at which he is losing fluid and from that calculation can estimate how much he should be replenishing. This strategy can be applied over a period of days to evaluate on a day to day basis whether the athlete is properly hydrating themselves post run. Last but not least, thirst is the last mechanism our body initiates to let us know we are hypohydrated. These 3 simples and cost effective mechanisms when put together make for a fairly effective strategy in assessing your level of hydration.
So onto how to approach hydrating yourself before, during and after training/competition. The general recommendation for fluid intake is ~ 5 to 7 mL/kg at least 4 hours prior to exercise (Sawka et al., 2007). This recommendation of course changes with the environment at hand, training intensity for that session etc. In terms of ingesting fluids during a training session or event, the American College of Sports Medicine recommends ingesting 0.4 to 0.8L of fluid per hour to the average marathoner. Now in terms of sodium and carbohydrate intake, it is not of vital importance to events 2 hours or less as your body has plenty to spare for the duration of the session. However events that are longer than 2 hours require adjusting and tweaking to account for sodium and carbohydrate intake. If an athlete is consuming carbohydrates the content of carbohydrates within beverages should be less than 10%. With concerns to post training and performance, the recommendation is 1.5L per Kg lost during training session (Sawka et al., 2007). With post training nutrition, it is important to note that sodium, carbohydrate and protein intake should predominantly come from food. And after everything is complete, it’s time to rest, recover and re assess!
Well we hope that you found this article helpful and that you will take into account hydration with your training. Although the tone of this article is geared more towards endurance athletes such as marathoners, it is still important for the average exerciser to recognize what level of hydration they are at.
Thanks for reading and stay tuned for the next article!
The Fit & Fed Team!