As the season moves through spring to summer, our hydration requirements change as well. It’s not uncommon for people to flirt with dehydration as the heat and humidity start to rise in spring and early summer. Most of us are creatures of habit and our habits through the winter don’t require as much attention to fluid and electrolytes. Step one is being aware of your training and racing conditions and step two is determining your fluid and electrolyte needs.
In the Lowcountry we have to factor humidity in with the heat. The higher the humidity, the more difficult it is for our bodies to control temperature. With a high concentration of moisture in the air there isn’t much room for sweat to evaporate, so make sure you are thinking about the humidity levels as much as the actual temperature. Until summer is in full swing, I would look at heat and humidity for a given day as well as the trend over the last 7 to 10 days. The cumulative effect of not hydrating properly is much sneakier than acute dehydration during a given workout.
As with most training and performance concepts, there isn’t a formula that perfectly fits everyone. Early studies from the mid-70s form the foundation of our current hydration guidelines even though their validity has recently been called into question. Tim Noakes, M.D., DSc authored a 2012 book titled Waterlogged in which he examines the hydration equation and what drives it. Dr. Noakes examines the physiology and the early studies in great detail but I’ll stick to a simplified explanation.
The hydration equation is about balancing water and electrolytes (sodium, potassium, calcium, magnesium). There are two terms frequently used to describe this equation when it is out of balance, hypernatremia (dehydration) and hyponatremia (over hydration). With hypernatremia there is a higher concentration of sodium compared to water in the body and with hyponatremia there’s a higher concentration of water relative to sodium. While people are aware of the dangers of dehydration, over hydration is just as problematic. The consequences range from impaired performance to possible death.
Now that I’ve regained your attention, let’s look at some basic steps to keep your equation balanced. Weigh yourself prior to and immediately after a workout session. If your bodyweight is the same as when you stared, you probably hydrated properly during the workout. If you weigh less than before, you may be moving toward dehydration and if you weigh more than you over hydrated yourself. When it comes to weighing more there really isn’t much debate, you simply took on more water than you needed and could be headed toward hyponatremia. When it comes to losing weight during a workout we’re talking about the basis for Dr. Noakes book Waterlogged. Current recommendations tell us as little as a 2% loss of body weight equates to a 10% reduction in performance. Dr. Noakes refutes this and presents a compelling argument. Top marathoners regularly lose 3% of their body weight without impacting their performance.
I will leave you with two recommendations. First, try to stay around the 2% rule for body weight loss and avoid finishing a workout heavier than you started. Dr. Noakes makes complete sense but if you’re going to train and race on the lower end of the hydration spectrum you better have a good grasp of exactly what’s going on and how you manipulate it. Second, make sure you’re taking in electrolytes along with your fluids. Most sports drinks have too much sugar, relative to their electrolytes, to consider them a perfect option for electrolyte replacement. Several brands have “salt” capsules that can be taken hourly along with the correct amount of fluid for you. As your training, and the weather, start to heat up make sure you’re adjusting your hydration requirements accordingly.