(To kick off this post, a few framing comments are needed...
1. I'm not a doctor, nutritionist, chemist, ... none of the above. The comments in this post are purely the product of my research on the web and of local resources including my personal experience. Please don't consider this to be medical advice in any capacity whatsoever.
2. Your mileage may vary - it's my hope that you'll add this information to your current mental database and therefore become even better equipped for sports nutrition success.
On to our regularly scheduled blog post...)
Hydration is about a whole lot more than just drinking water. I'm sure you probably already know that. But, the real question is this - how can you be sure that you've got the right formula to have confidence you're meeting your endurance sport hydration needs? Let's see if we can't add a few bits of info to answer this question and at least get closer to an answer.
A few things to consider in long course endurance racing.
• You can have a stomach full of water and still experience dehydration if you are electrolyte depleted.
• Salt capsules are not the same as electrolyte supplements... they both contain salt, but the electrolyte supplement also contains (generally speaking) potassium, calcium, and magnesium.
• It's unlikely that in endurance racing (half-ironman or longer) at higher temperatures you will get your electrolyte and hydration needs both met through a single product (drink, gel, powder). You may be one of the lucky ones, but it's unlikely.
So, it seems there may be some complexity here then. Let's talk about a few basic strategies that have worked for me.
1. Separate your hydration needs from your caloric needs! You may address them both through the same products, but consider their fulfillment separately in your planning. I'm not going to discuss caloric intake needs in this post at all - we'll discuss that one later.
2. Know your sweat rate (how to determine is below), and estimate your electrolyte needs. The sweat rate test is relatively easy, the electrolyte need determination may take some trial and error.
3. Know what products you use, what products will be on the course for your races, and make sure that you have a specific timetable at which times you will consume what quantity of what product. It's important to be a planner in this endeavor if you want to be successful.
4. Practice your hydration strategy in your training! Don't ever think that you'll just magically nail it if you're not planning and testing during training - we train to long and hard to leave something as important as hydration to guesswork.
Have you done a sweat rate test? If not, you should consider it.
Here's how you'd do it - from an article originally published in Runners World.
1. Weigh yourself nude right before a run.
2. Run at race pace for one hour, keeping track of how much you drink (in ounces) during the run.
3. After the run, strip down, towel off any sweat, and weigh yourself nude again.
4. Subtract your weight from your prerun weight and convert to ounces. Then add to that number however many ounces of liquid you consumed on your run. (For example, if you lost a pound and drank 16 ounces of fluid, your total fluid loss is 32 ounces.)
5. To determine how much you should be drinking about every 15 minutes, divide your hourly fluid loss by 4 (in the above example it would be 8 ounces).
6. Because the test only determines your sweat losses for the environmental conditions you run in that day, you should retest on another day when conditions are different to see how your sweat rate is affected. You should also redo the test during different seasons, in different environments (such as higher or lower altitudes), and as you become faster, since pace also affects your sweat rate.
Now that you know your sweat rate, you can begin to consider your electrolyte replacement needs.
From what I've read/observed, if your sweat test result yielded your needs to be 24oz of fluids per hour, a fairly average hydration formula would look something like this - 24oz of fluids per hour plus electrolyte supplements containing ~600mg of sodium (also including brand-specific proportions of the other electrolyte ingredients mentioned above). I'm sure this estimated baseline could be debated, but I'm willing to put a stake in the ground and recommend this as a starting point.
You can now begin to experiment with a few different electrolyte replacement products using your sweat rate result as a baseline for electrolyte replacement needs.
Remember that although electrolyte supplements (i.e. Endurolytes, S-Caps, SaltStick, Lava Salt, Thermolytes) may appear identical, there are DRAMATIC differences between them. As an example, lets look at the sodium content of each of the above caps (we spend so much time looking at sodium as it's the electrolyte in highest concentration in our sweat & urine):
Lava Salts: 158mg
Clearly quite a difference, and very important to keep in mind when planning for your electrolyte needs!
Personally, I'm a fan of Thermolytes, but also use SaltStick caps on occasion. It's very rare you'll see me without a little container of them on any long training effort. Visit your local endurance sports store or running/tri club and see what they have to say. Experiment to find your optimal mix.
Here's another possible approach that may yield some assistance as you determine your needs during long intense training and racing situations...
• If your drink "tastes" too "watery" you may want to increase your salt intake. For example, some athletes have had the experience that "the volunteers at that last aid station aren't mixing the Gatorade strong enough, it's way too diluted!" Well -- usually the drink's mixed right and that is your body's way of telling you that you're in fact diluting your own electrolytes, internally.
NOTE: There is no "salt craving" associated with this "watery taste." In fact, it's more a feeling of "water aversion.", as in it just doesn't feel/taste like something you want to drink.
• If your drink tastes too "sweet" or concentrated you may need to increase your water intake -- this is your body's way of telling you that you're dehydrated. If you come away from an aid station thinking the drink has been mixed too strong, or things simply taste too sweet, syrupy, or concentrated, your body may be telling you it needs water.
There's certainly more to write in the future about this, but hopefully this serves as a solid starting point if you were looking for one. If you're a bit befuddled trying to figure this all out, believe me, you're not alone... but once you get it figured out, you'll never be happier and will be en route to some outstanding performances!
(huge thank you to the many contributors to this information! Runnersworld.com, slowtwitch.com, and many many endurance athletes/coaches throughout Texas and California)