Athlete hydration was top of mind as I left USRowing Youth National Championships in Sarasota, Fla., last weekend. At 5:30pm on Saturday—Day 3 of the four-day event—the outdoor digital thermometer at the race venue’s entrance read 91 degrees. Hot! Hot for spectating and certainly hot for racing, particularly at a venue with no shade.

Earlier that same day, I was weightlifting at an indoor/outdoor facility (think garage style gym with two opposing bay doors that help, blessedly, with airflow) and a group of local high school athletes walked in. The weightlifting coach asked one of the boys if he brought water.

“Nope,” was the immediate reply.

A case of an athlete with no water at practice—not to mention, practice in extreme heat! (Points, by the way, to the coach who instructed the athlete to get water from the adjacent gym before he started to train.) Meanwhile, stories from the regatta venue included teams instructed to fly wearing compression socks, excitement about investing in technology including recovery boots and even one about a rule against swimming for fear of inducing fatigue.

I love hearing how teams are prioritizing recovery. I love meeting parents who want to learn more and seeing coaches look out for their athletes. My question is where does hydration fall into the mix? As athletes, how do we relate to it? How do we understand it? Where do we place it on the list of moving pieces that add to or detract from performance?

Facts About Hydration and Performance Decline

Water is essential for life. In The Encyclopedia of Natural Medicine, this is the opening statement following one of nine main principles for optimal health identified by world-renowned naturopaths and co-authors, Drs. Michael T. Murray and Jospeh E. Pizzorno (2012). Water and salt combined are essential for metabolism, detoxification, and hormone, immune and nervous system function (Karr et al., 2023). When one or both are lacking, we can experience physiological and (no surprise)
performance declines.

Dr. Marc Bubbs, ND, cites the potential impacts of progressive dehydration on performance as follows:
• Fluid deficits with as little as two percent bodyweight can impair cognitive function and aerobic output.
• Dehydration at three to five percent can hurt sport-specific technical skills and anaerobic output.
• Severe dehydration, characterized as fluid loss at six to 10 percent bodyweight, can decrease cardiac output, sweat production/thermoregulation, and blood flow to the muscles (Bubbs, 2023).

Why does this happen? What can we do?

Physiology Basics

When it comes to maintaining hydration status, salt intake proves supreme.

Fluid loss through sweating is the body’s way to self-regulate. In technical terms, this thermoregulation is how we maintain our core temperature. The process is governed by the hypothalamic thermoregulatory center—“the body’s thermostat”—which detects changes in core temperature (Osilla et al., 2023). When core temperature rises, due to heat or exercise, the body’s internal thermostat sends signals that activate the sweat glands, induce sweating and ultimately aim to bring down core temperature.

Here is what is important for athletes: The fluid we see on our skin—the sweat—is coming from blood plasma. Our blood, in the words of sports scientist Andy Blow, is “very salty” (Ahmed, 2022, 10:50). So, not only do we experience a decrease in blood volume with sweat, but we also lose sodium, the element we learned earlier is essential for overall functioning and health. From a performance perspective, this results in added stress to the cardiovascular system, increases in heart rate and can even impact good old rate of perceived exertion (RPE) (Ahmed, 2022).

To sum it up nicely: “Heavy sweat losses impact blood volume which then impacts performance. So, hydration is really all about the maintenance of decent blood volume while you’re exercising,” says Blow (Ahmed, 2022, 11:20).

Enter salt intake and how we can strategize for hydration.

Electrolytes: An “aha” moment (and a little more science)

In all my years training and in my own efforts to optimize and supplement smart, I have spent lots of time comparing electrolyte products. One aspect that consistently stood out was the variation in sodium and potassium content between brands.

In listening to Blow talk about salt and sweat, I had a personal “aha” that cleared up a longtime source of confusion rooted in the variation of sodium-to-potassium ratios between electrolyte drink products and brands. Blow explained that potassium is the body’s predominate electrolyte inside the body’s cells, contributing largely to intracellular fluid. Sodium, on the other hand, is the major electrolyte outside the cells. It is prevalent in extracellular fluid and, importantly, lost in high volumes through sweat (Ahmed, 2022).

So, sweat has an impact on blood volume, and salt, with its ability to effect water retention, can have an impact on blood volume and sweat.

The main takeaway from where I sit is there is no need to get caught up in the minutiae of potassium in electrolyte drinks, at least not for well-nourished athletes who train and perform in the heat. With regard to strategic hydration, the main takeaway leads to my favorite actionable recommendation from Blow, namely, pre-hydration with a “very strong” electrolyte drink.

“Having a lot of sodium in a drink pre-exercise can help your body move the fluid from the gut into the blood stream and hold it there, so you’re boosting your blood plasma without horribly compromising the sodium levels… You’ll need to do that about an hour before exercise,” he says. (Ahmed, 2022, 19:20)

Do you see how the pieces fit all together?

Some Practical Considerations and Other Debate

Hydration, just like nutrition and recovery, is an art and a science when it comes to athletes and performance in sport. It can be nuanced and may warrant experimentation (away from competition, not in the heart of a big game or race!) and planning. Keep it as simple as possible, and respect (don’t neglect!) it. Remember the following:

Respect variation.

Individuals have different sweat rates and varying concentrations of salt in their sweat. Consider what it would mean to personalize your hydration strategy and plan for something like an acute change in climate or competing in heat. What do you need? What steps do you need to take to prepare? How will you stay accountable and ensure follow through?

Understand sweat loss.

Acute sweat loss is one of the “biggest levers” that impact hydration (Ahmed, 2022). Be mindful of variables like workout duration, workout intensity, training environment and climate changes, particularly big swings in temperature that will impact your sweat.

More is not better.

Notice that Blow’s recommended pre-hydration strategy included a high concentration of electrolytes. This is important to reiterate because hyponatremia, caused by an excess of water in the body, is both risky and real. When we talk hydration or pre-hydration, we must be mindful to not dilute the whole-body system. Consider making changes incrementally and monitoring how your body responds, or seek professional help.

Consider hydration a teaching tool.

For younger athletes or those looking to up-level their commitment to performance in sport, hydration could offer a practical and easy way for an athlete to expand how they build confidence or what they put into their sport. Help them select the right electrolyte drink. Then, give them the responsibility to get their water bottles ready (water plus electrolyte mix) and remember to pack them for practice.

Know that there are two schools of thought.

Controversy exists between those believing in the “drink according to thirst” rule of thumb and those who think that the rule is a set up for trouble. Thirst, says the second camp, indicates dehydration and is a sign that it is already “too late.” Keep this in mind when you listen to experts or seek out advice. Remember that individualization applies.

References

Ahmed, W. (Host). (2022, July 20). Sweat, salt, and hydration: Sports scientist Andy Blow covers the essentials of hydration (Episode 181) [Audio podcast episode]. In WHOOP Podcast. https://www.whoop.com/us/en/thelocker/podcast-181-sports-scientist-andy-blow-hydration/

Bubbs, M. (2019). Peak: The New Science of Athletic Performance That Is Revolutionizing Sport. Chelsea Green Publishing.

Karr, T. J., Bell, K., Guptha, L. S. (2023). Our Journey with Food (3rd ed.). Summerland Publishing.

Murray, M. T., & Pizzorno, J. (2012). The Encyclopedia of Natural Medicine (3rd ed.). Atria Books.

Osilla, E. V., Marsidi, J. L., Shumway, K. R., & Sharma, S. (2023). Physiology, Temperature Regulation. In StatPearls. StatPearls Publishing.