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Congratulations! You just signed up for your next big event—now it’s time to figure out how to show up to the starting line as the best possible version of you. Chances are you’re about to figure out your run training plan. Maybe you’ve even hired a coach to guide you through this. It’s obvious to most people that an organized, intentional, and progressive plan for your running is the way to be prepared for a race. So why don’t more people do that when it comes to hydration?
Most runners know to replenish fluid they lose during exercise to avoid dehydration. Dehydration can decrease performance and lead to overheating or heat stroke. Additionally, runners need to prevent hyponatremia, a lack of sodium in the blood. This state can cause water buildup in the lungs or brain, with symptoms like shortness of breath and disorientation. Both of these situations can, in rare cases, lead to severe consequences like coma or death, underscoring the importance of properly managing your H2O and electrolyte intake. While you do lose other electrolytes in your sweat, sodium is the big one to manage, especially because of the risk of hyponatremia. We’re going to focus on hydration during your race and training runs, but clearly you don’t want to start a run at a deficit and it is just as important to hydrate post-run to maximize your recovery.
Every person is unique, so you have to put in the work to determine your own hydration needs. But where do you start? The two main factors to pay attention to are sweat rate—how much you sweat—and sweat concentration, which is how salty your sweat is. You might intuitively have an estimate of where you land on either of these, but let’s get more specific so we can build a plan.
Figuring out your sweat rate is pretty straightforward. Before a run, urinate, and then weigh yourself in the nude. Go on a run for an hour – this is a nice round number that’s easy to prorate later and anything much shorter or longer can be influenced by too many other factors. When you get back, strip down to the nude, towel dry, and weigh yourself again before you consume any food or drink. Additionally, if you did consume any food or drink on the run, you’ll need to have those weights and factor them in—another reason to keep the run to about an hour. The difference in weight from before the run to after the run is roughly how much fluid you lost in an hour at the effort you ran and in the climate you ran. It’s important to note that sweat rate can be dramatically influenced by your own fitness and the intensity of effort, as well as air temperature, humidity, altitude, and your acclimation to those environmental factors. Because of this, scientists have seen athletes lose anywhere from 0.5 liters per hour to 2.5 liters per hour. Additionally, you should measure your sweat rate more than once. Do your best to replicate the environment you expect to experience on race day and test throughout your training as your fitness improves. Log these tests so you can reference them later and hopefully see a pattern emerge.
Sweat concentration is a little trickier to measure. The upside is that it is less influenced by external factors, so it doesn’t fluctuate as much. However, it does vary dramatically from athlete to athlete, with some losing as little as 200 mg of sodium per liter of sweat and others losing as much as 2,000 mg per liter. There are various scientific ways to collect and measure sweat. This can range from at-home patches or sensors to fairly simple tests administered by a professional, to extremely elaborate tests. As you might expect, the price of all of these can vary dramatically. Depending where you are as an athlete, these options might make sense, but there are also simple (and free) ways to self-assess your sweat concentration by thoughtfully answering a few questions. Do you often finish runs with salt stains on your clothes or skin? Do you noticeably crave salty foods during or after a run? When you get sweat in your eyes, does it burn really badly? All of these are signs you might be a salty sweater. Additionally, if you’re someone who has struggled with muscle cramps, especially in hotter conditions, or if you feel like your performance is dramatically more impacted by heat than others, these might also be signs of a high sweat sodium concentration.
Okay, so you know how much you sweat on a run like the one you measured, and you have an idea of how salty your sweat is. Now what? Your goal should be to replace most—but not all—of the fluid lost while running. It would be nice if things were as simple as drinking a liter of fluid for every liter you sweat, but that risks hyponatremia, and would likely be overriding your own thirst level. Ideally, you should be drinking at a consistent rate during the run (think IV drip, not chugging the whole bottle) to stay in-tune with your body and adapt to any changes. When it comes to sodium, replacing 1000 mg per liter of sweat lost is a solid place to start. If you’re a salty sweater, you’ll likely need more. Keep in mind that while a drink mix is a great way to manage sodium loss, you’re also getting sodium from any food or sports nutrition you consume. Dialing in these sodium levels comes from practice and learning how to listen to your body.
It’s not realistic to perfectly plan and nail your hydration for literally every training run. So instead, set aside a specific 7-10 days of training early in your training cycle. Look at 6-8 weeks out from your race for a good window, or you could tie it to a training camp or training race if you have one planned. Thoroughly plan your hydration and make your response to it the focus on these runs. Then, after each one, document how much you drank and how much sodium you consumed, along with any notes on how you felt or performed. Cover the basics, like if you literally had enough access to hydration, but also look for nuance. Did you feel sharp? Both in your physical performance but also your mental acuity. Also, think about how you felt after the run. Were you particularly rundown or did you bounce back quickly? Remember, you’re getting sodium from your fuel, not just what’s in your bottles. After this specific hydration training period, you should have a solid idea of what works for you. As you get closer to your race, your run training and fitness should have evolved and it’s worth a second hydration examination. So, approximately 2-3 weeks out from your race, set aside another 7 days to plan, log, and analyze your hydration. You want to use this to confirm the strategy and sodium replacement products you’re going to use on race day while addressing anything specific to the race. This could be estimated pace or effort, terrain, temperature, time of day, or any factor that could influence your hydration. You should also be using whatever bottles, handhelds, vest, etc. you plan to use that day.
The big event is finally here. You’re trained and prepared to execute the best version of you on this day. As you finalize all your preparations, make sure you stay hydrated the week of the race. That means electrolytes, too, not just water. Also, there are just a few logistical things to take into account. Depending on the distance of your race, you’ll likely be dealing with aid stations and/or crew. Even if your favorite drink mix aligns with what’s offered at the aid stations, you cannot guarantee it will be mixed at the suggested ratio. It might make sense to utilize the aid stations for plain water and either carry your drink mix or have your crew prepare bottles to your plan. Most of all, be prepared to roll with the punches. Racing is hard and you’re likely to have to make some changes on the fly. Having your hydration dialed in advance is one less thing to worry about.
Congrats on crushing your race! Even if things went perfectly and especially if they didn’t, you should reflect on how your hydration strategy played out. Did you stick to the plan going in? What variables forced you to make changes? It could be as simple as noting where in the race your favorite flavor of drink ceased to be your favorite. Make a note of all of this so you can go into the next big event with an idea of how you can make it even better. Being intentional is how to improve in this sport and life.
Did this article make you thirsty? Claim your free LMNT gift here with any purchase and get your salt on!
