Triathlete and runner here. Not quite sure what my bike sweat rate is but during an almost 3hr elapsed time run. I consumed 2.6L over the run and thought it was going to be enough, but the final 5 miles were terrible and I got home and still lost 7 lbs. I measured 5.75L total loss.
Today on a quick 40min run it mathed out to 2.2L/hr.
I’m struggling to come up with a reliable fueling and hydration plan to keep me strong as well as holding off hyponatremia. I suffered from hyponatremia at Kona in 2022, and since then I;ve been worried about messing it up again. The following summer I would end up with severe dehydration on several occasions. I’ve pinned it on a subconcious worry about overdrinking so i underdrink. I also notice I NEVER get thirsty.
My fueling plan lately is formula 369 ~ 595mg sodium per 100g of CHO (per hour), so my best guess is that im way under sodiumed. I’m just looking for advice on how NOT to mess it up on long days and when my brian isn’t working well on the hardest of days and i start losing track of numbers.
What do you wear on your top half. Sweat only cools you if it can evaporate. If it sits on your skin or is dripping off, then it’ll hinder evaporation reach saturation and not cool you. This can increase sweat rate as you are not cooling through sweating.
Hyponatremia is terrible - I feel your pain as I’ve dealt with it dozens of times - heat stroke, heat exhaustion, been hospitalized twice (should have gone to the hospital many times but sucked it up and dealt with it at home). In addition to nausea and weakness you can drop dead! I’ve not experienced it at all since I started salting my Gatorade on hot days (low-mid 80s I’ll use 1/2 tsp; upper 80s or higher 1 tsp). One tsp of salt is about 5,000 mg, so for a single large bike bottle I mix in 1 tsp of salt and 1/2 tsp potassium chloride to a half scoop of Gatorade. Not particularly tasty for the first hour, but after an hour it is delicious. Also carry one bottle of water (nothing added). Depending on duration and temperature I might bring a second bottle of salted Gatorade. You could also take salt tablets (if your bibs have thick latex leg bands you can fold one up (like a cuff) which creates a crease where you can stow the tablets).
That’s very dependant on humidity, temperature, how hard you’re working, what the wind is doing, which direction, how long you’ve been sweating, your recent diet etc. It’s not a fixed value.
I’ve been testing year round using an HDrop and just had a Precision Fuel test to compare it to. Honest answer - it varies some, but not that much. The amount of sodium you lose and amount of sweat varies by a huge amount, but sodium per liter not as much, at least for me. And plus, get in the ballpark and you’re fine - you can deal with some more or less fine. (Side comment - I don’t have blood pressure issues and extra sodium doesn’t cause problems for me, if you’re different, YMMV…)
What you do have to pay attention to is cold weather - where you’re primarily losing fluids through your breath and not sweat, thus not losing sodium. So, can cut back in those scenarios but it also hasn’t hurt me to just use a fixed value year round.
I’m also a very heavy sweater and ended up in emergency room one time. I make a very conscious effort to hydrate more during the days leading up to event or training. I’ve also started drinking much higher sodium level fluids (i.e. LMNT or Mortal Hydration). I live in the US (south w/very high humidity). When I run, I try to wipe sweat off my arms, chest and stomach with hand - similar to squeegee. Ice, when able, on the back of your neck and wrists. Begin drinking early into your training or event. Stay on top of it.
Just a note that 1tsp of salt is about 5g of total weight but contains about half that in sodium. So if you’re trying to replace lost sodium make sure you’re looking at that and not the total weight of Sodium + Chloride
I’m a heavy and salty sweater.
The first thing I learned is that sodium is there to help your body absorb water. It’s not related to carbs at all.
I spent some time on long endurance rides testing out different concentrations on sodium per liter of water. Basically I kept increasing the sodium concentration until I hit the point of gut disturbance (when you get back from a ride and have a GI event), then backed off a tiny amount.
So I keep my sodium/water intake separate from my carbs intake in planning and execution. Not sure if that helps, but it might be worth looking into.
If it helps, I’m at about 1200mg of sodium citrate per liter of water.
For reference, I use tailwind which has 1240mg sodium/100g of CHO
595 seems pretty low unless you’re a very non-salty sweater.
I sometimes supplement my tailwind with gels/other forms of carbs, in which case I’ll add an appropriate amount of sodium citrate (NOT CHLORIDE) to get back around the 1200 mg/hr range.
People are different on their hydration and sodium needs and also what effects arrive when they lack either. Obviously tests can be performed for both, plus some good ol’ trial and error.
