Hydration, How Much is Enough

I wanted to talk about exercise and hydration, especially since we just had quite a heat wave here in Northern California and a lot of people were talking about feeling awful after their workouts. What I'm referring to is the loss of energy and that heavy gut feeling that happens post workout (usually after long activities such as runs or rides) due to inefficient fluid intake. 

First rule when  trying to stay in peak condition for optimum performance is as Dr. Stacy Sims says, "food in your pocket, hydration in your bottle". Too many people put all sorts of sports powders or drinks in their water bottles that end up causing GI issues, and poor performance. In reality these solutions won't hydrate you like they claim, and can actually cause dehydration instead. 

Body Process of Hydration

Let's look at the process of hydration to get a better understanding as to why many hydration solutions on the market do not actually hydrate you. Remember that the reason we need to stay hydrated is to keep our body fluid levels high enough so we can use the water in our system to get rid of the heat we produce and cool us down while exercising. Essentially, while the blood is circulating the body it brings fuel and nutrients to the muscles and takes away waste products and heat. The blood continues it's circulation by moving out to the skin where it dumps the heat through sweating and ultimately evaporation. In order to sweat, water is taken from the plasma portion of our blood (liquid part), then sent through the skin where it can then evaporate and ultimately cool us down. 

As you sweat more you feel cooler, but your blood plasma volume is shrinking. When you don't have enough fluid in your body to keep the blood plasma volume balanced that's when things start breaking down. Your heart will have to beat faster to deliver the same amount of blood to your working muscles, and your core temperature will begin to rise. Once these things start to happen you will begin to feel fatigued, your performance will decrease, and you may not be able to finish your intended workout.

Chemistry Behind Hydration

Yup I just said that dreaded word (for many not all of us, or maybe just me): chemistry. How then does the water we ingest get into our bloodstream and what should be in that bottle we are drinking? Did you know that 95% of our fluid absorption happens in the small intestine? The small intestine is responsible for monitoring the Osmolality (amount of sodium) of our blood. To do this it is very sensitive to the levels of water and sodium that pass through. Normal blood plasma osmolaltiy is between 275 and 295 milliosmoles(mOsm), (Dr. Stacy Sims, ROAR, 2016). In order for our intestine to absorb the fluid you send to it, the osmolality needs to be lower than that of your blood. According to Dr. Sims, she suggests it be between 210 and 260 mOsm. 

When the osmolality of the fluid you take in is higher than that of your blood, it's considered too high a concentration and your body won't let it through the intestinal walls. Instead the high concentration will cause the opposite effect. The intestinal cells will start to pull water from the blood vessels in order to dilute the solution you just sucked down into your gut. This is how dehydration occurs and also where the GI upset comes from. 

The make up of your drink needs one more component for this process to work optimally. So far we have talked about good old H2O and Sodium. What will make it easier for the sodium to cross the cell wall is to have glucose right there with it. Be careful though, as many of the "sports drinks" on the market have too much sugar (meaning high osmolality), or the wrong kind of sugar and thus a slow emptying occurs. Remember high osmolality causes your body to draw water out of the blood and into the gut . 

What's in a Sports Drink?

Now that you understand how hydration works, don't worry you don't need to remember all that crazy chemistry stuff. Let's look at the sports drinks that you may be using, like Gatorade, Powerade, UCAN, Cytomaz, Hammer, and a whole sleuth of others. In most, not all people these drinks cause dehydration and stomach upset. These drinks have the following:

Carbohydrate solutions of 5-8%, which is about 12-19g of Carb per 8 ounce serving

Osmolality is around 300-305 mOsm

Sugars used: maltodextrin, fructose, sucrose

Sodium concentration of 52-110 mg per 8 ounce serving.

What Should be in My Sports Drink?

According to Dr. Sims and her research in the field of sports hydration, she recommends the following:

Carbohydrate solution of 3-4%, which is 7-9.4g of Carb per 8 ounce serving

Sugars used: glucose and sucrose at 7-9.4g

Sodium concentration of 180-225 mg

Potassium of 60-75mg (this can also help sodium transport across cell membranes)

She suggests using OSMO Hydration, ClifShot electrolyte drink, GU Hydration Drink mix, Bonk Breaker Real Hydration, as these products have the proper concentrations.

What about plain water? 

Plain water, because it contains no sodium, potassium or carbohydrates, lowers the ability of the body to move it out of the intestine into the cells. The water will many times just sit there in your stomach and slosh around, like it did for me as a runner. Another thing that can happen when the level of the water gets too high in the intestine, it will signal the body to urinate without absorbing any of it, and then you are back to where you were before drinking the plain water. 

How Much Should I be Drinking?

Now that you understand what type of fluid you should be drinking, let's talk about how much you need to be taking in. Generally speaking drink to thirst is recommended (women please note: during the high hormone phase of their cycle--5-7 days before their period starts--you will not feel the need to drink as much as the rest of the time during your cycle. Drinking to thirst is generally not advised for you at this time). For a more formulaic way to get properly hydrated, read on.

When the temperature is at or below 75 degrees Fahrenheit: Drink 0.10 ounce per pound of body weight. This is roughly 12 ounces for a 120 pound person.

When the temperature is above 75 degrees Fahrenheit: Drink 0.15 ounces per pound of body weight. 

Do be careful not to exceed 25 ounces of fluids per hour for a 130 pound person. You'll need a little more or a little less if you are larger or smaller than that. 

Lastly, you've probably heard it said to weight yourself before you exercise, then again after you exercise, and for every pound you lost you need to replace it with 16 ounces of fluid. That doesn't take into account the amount of fluid you drank during your workout, nor does it take into account the food that you consumed that may still be sitting in your gut, or the fact that your body just used up some of your glucose and fat stores. This system again may work for some, but is not recommended. 

Keep in mind these are general suggestions, a good starting point, but not a one stop fix all. Experiment with your hydration and let me know what works for you.

Thanks for reading.