Hydration Strategies for Runners - Mastering Fluid Intake for your Next Race

November 14, 2023

After writing yesterday's article about the upcoming Clontarf Half Marathon, it got me thinking; do runners know how much to hydrate for a given race? I'll be honest, even with 15 marathons, and god knows how many half marathons and other races, and long runs, I can't say with any great confidence that I know the answer to that myself. A friend who I run with, Gareth, made a great point for a simple calculation based on liquid consumption. Weigh yourself pre-run, down to the gram, weigh your drink, and then weigh yourself post run, and weigh your drink post run. The delta (the difference between the 2) is basically how much fluid you consumed during a run. This is brilliant advice, and something we should all do.

Be that as it may, most of us won't. As runners, we tend to throw caution to the win, and run to feel, and measure our fluid intake by virtue of how thirsty we are. It is somewhat ironic that we don't measure our fluid intake or efficiency considering we tend to track everything else. Perhaps it is because Strava doesn't yet have a H2O consumption metric. To be honest, we all know why... that would lend it self to people asking how many miles to you get to the gallon, and invariably people would drink less in the false hope that they would be more efficient.

Regardless of how many miles we can do during training off very little water, the reality is our efficiency on race day will be directly correlated to how well we are hydrated. Every one of us is a different shape and size. Every one of us has a different level of fitness, and we are all at different stages of our lives, with different stresses, and different diets. There is no real one size fits all, because there can't be.

Looking ahead to the Clontarf Half Marathon, and any race for that matter, you need to not just plan your pace, but also plan when you're going to hydrate and how. As I mentioned, I know now that the race organisers, in a push for greater sustainability, use hard plastic reusable cups. This is great for the environment, but it isn't great for runners. With that in mind, I said I'd put a list of the top 7 things you need to do when prepping for a race when it comes to hydration. Before I do, there is a health warning here, I am a casual runner and sharing tips which are general. For advice specific to your needs, see a medical professional. At the end of the day, I'm a runner like you all who is just trying to help!

  1. Have a bottle of water or your drink of choice on you rather than depending on cups. You can hydrate at a specific rate (time) and better control the amount of fluids you are consuming.
  2. Take the thinking out of it and set your watch timer at 15-20 minute intervals. Every time it goes off, hydrate.
  3. Everyone's fluid needs are different. Some may need more fluids, some less. Calculate your "sweat rate" by weighing yourself before a 60 minute run. There is a bit more science to this, but this is a good start.
  4. The goal is to offset hydration, not replace all the fluids lost. This is especially true for heavy sweaters as the body can only absorb so much fluid per hour (about 1 litre or less). If you're like me and sweat enough to fill a swimming pool inside your first 30 minutes, know that this is going to happen and hydrate accordingly.
  5. Walk to get the fluids in. Unless you have mastered drinking on the run, it is better to get the fluids in you rather than on you. You will more than make up the lost time walking over the duration of the run.
  6. For those with a sensitive system, consider drinking fluids more frequently, but in smaller quantities. Perhaps 2 sips every 10 minutes.
  7. Watch the color of your urine when you go to the bathroom. If it is "clear" that means you are drinking too much. If it is dark, you need to drink more. If it is light yellow like lemonade, your hydration is just right.

These tips are general and should have you at least thinking about how much you hyrdrate. There is also a handy little website to check all this stuff out on Daily Water Intake Calculator.

If you are running a race soon, or just reading this to get an idea around how you should hydrate, best of luck, and keep hydrated!

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