Hypno Toad

As I rider that struggles with hot rides and somebody that likes to challenge myself on endurance and ultra rides ... I've spent very little time looking at information about sweat loss and hydration. When riding, I drink when thirsty and have a bottle or two with electrolyte mix and call it good.

I was out for century last week with temp around 100F and high humidity. I left early morning to avoid the heat of the day ... then made a bad route choice, I lost a ton of time and had a very slow drag over the lost 20 miles getting home during the peak heat of the day.

Anyhow ... with lots of time to think on this ride, I was thinking about hydration and how much I'm losing to sweat. This is interesting stuff:

https://ksi.uconn.edu/wp-content/upl...Calculator.pdf

I know that I'm losing about 1l per hour ... I'm a little surprised to see this deficit while drinking a large bottle per hour.

Looking forward, I'd like to find better information about hydration strategies for endurance and ultra rides to keep myself from falling into a bad hole. I've done some searching, but haven't found anything helpful. Please share any resources you know about for hydration strategies on hot long rides. Thanks!

Iride01 

Long time when starting to ride regularly I didn't know squat about hydration. I did however think to weigh myself before and after a ride. Sometimes I was losing five pounds on a ride. Just fluid loss from sweat. That is a dangerous amount of fluid to loose at one time. Now that I'm better at managing my hydration, I seldom see more than half a pound difference immediately before and after. Unless I pee before weighing. <grin>

Key thing is just to drink periodically. If I look down at my timer and it's near a multiple of 10 minutes, then I'm definitely taking a gulp or so because I'm thirsty. Sometimes in very hot weather I get thirsty in between every ten minutes and I'll take a gulp or two then also.

I can pretty much gauge how much I'll need for any temp I ride in. I guess after years of watching my self closely by weighing before and after a ride it became intuitive. Generally I'll use 24 oz in 50 minutes of riding. Over 95°F and that will be gone in 40 minutes. Over 100°F will empty that bottle in 30 minutes. So I guess the link pretty much is teaching one to do what I already do from experience.

I've heard some talk about going for an hour without taking a sip. I can't do that even in sub 60° F weather which is cold to me. I also hear some say drink only when thirsty. However I need a reminder. Being used to looking at my timer and seeing it come up on a 10 minute multiple just serves to remind me to check if I'm thirsty. I almost always am thirsty. But without the timer, I might go thirty or more minutes before realizing how thirsty I really am.

Carbonfiberboy 

Then nothing. Sweat rate doesn't really matter and looking at sweat rate calculations will have you using too much electrolyte and making yourself sick to your stomach. What matters is what you put back in. I also use a timer as a reminder, though I don't always drink water. I set mine to 15'. If I know I'm somewhat screwed on hydration, I'll pick it up to 5 swallows every 5 minutes, which I think is as fast as I can get the water back out of my stomach. The main thing you want to watch on long rides if that you better pee at least every 3 hours. You might find you always have to pee after the first 3 hours, but the second and successive 3 hour markers might be a different story. If I ever go 3 hours without peeing, I find a source of water and shade and just sit there and drink until I pee. You don't want to actually replace the all salt you sweat out, you just want to replenish what's in your bloodstream. Taking or using electrolytes will make you thirsty and you'll then drink to thirst and be hydrated in a balanced manner. I see you use an electrolyte mix. That can be just fine as long as it's not too strong. Bring extra for your refills.

My 15' timer isn't really for drinking - I drink all my food, so it's really for "eating." I "eat" every 15' which keeps my blood sugar even. When the timer goes off, I drink from my food bottle, and sometimes also drink plain water if I'm thirsty. My electrolytes are separate from my water and food. I take some every hour if it's at all warm and I've been drinking water.

Hypno Toad

Thanks for your sharing experience - I'm clearly not keeping up on my hydration and that can really hurt on rides more than a couple hours long.

The first time I weighed in pre/post ride, I'd lost 5 lbs on a 2 hour ride ... 5 lbs down and I drained two 26 oz bottles. FWIW - this is Minnesota summer - hot and humid.

Carrying enough water is going to be an increasing challenge ... for long rides, I use a 3l CamelBak plus 2-3 large bottles.

Reality check: I will need to stop to refill bottle more often to keep hydration level.

Also thinking about preride hydration strategies ...

DrIsotope

I'll give some insight from someone who routinely endures actual heat. Have I taken in over 2 gallons of fluids in one ride and still lost +5lbs? Yep. A 25oz bottle every 15 minutes, and it still wasn't enough. Not unusual in the summer to taken in two 25oz bottles per hour at a moderate pace. The notions of drinking enough to take a leak every 3 hours is well... amusing. I've done 6 hours on the bike, drinking non-stop, and finally used the restroom two hours after I got home.

In my experience, it's not so much a "hydration strategy" as it is an exercise in logistics. Up past 100º, I can expect to need at least 1oz every 2 minutes. If the wind is wrong, or the sun is coming wide-open, it can reach 1oz per minute. I don't know how to adjust that for humid conditions-- we regularly drop into single digit humidity here, so dry that the act of breathing is dehydrating.

I don't do electrolytes during the first hour, no point. I try to get a full bottle in during the second hour, then it's at least 1 bottle of Gatorade, etc. per hour for the remainder, and as much water as I can get my hands on.

berner

A lot may depend on where you live. The is hot and there is hot and humid. I lived on the Mississippi Gulf Coast for 10 years or so where the typical summer temps were 93 F and the relative humidity was also 93 %. This is much like standing in a shower. At fist I thought I was going to die but did get used to heat and humidity. I even played tennis regularly in the noon day sun but did drink much water. Interestingly, one of my tennis friends born and bred in the South, would barely produce a bit of a sheen on his brow while I sweated rivers. Back in New England, it can be hot and humid but at a lesser level. I don't need as much fluid intake but do weigh myself before and after a ride and don't let myself get any lower than one qt. down, say 1 1/2 to 2 pounds. The capacity to deal with heat and fluid intake will vary with acclimation.

Trakhak

My strategy for hydration was to drink whenever I noticed the moisture in my mouth starting to thicken. Now it's to keep drinking enough to prevent that ever happening.

Iride01 

I've always been a sweater. I sweat gallons at the slightest bit of outdoor activity and I've always been an outdoor person and worked and played in the heat extremes of summer all my life. Maybe it's as berner suggests and a persons origins or heredity play a part in your adaptation. I'm from the southwest shore of Lake Michigan but moved to the South when 9 yo. Yet many others of my friends down here don't sweat near as much as I. Even my own son is amazed at how much sweat drips off me like a overworked horse when I stop at crossings while riding.

I also feel there is a large variable in how much salt and other electrolytes some people lose from sweating. I don't have any salt buildup showing if my sweat soaked clothes dry before getting laundered. I've had a few friends that could let their clothes dry and they'd be stiff as if starched. Maybe part of the issue there is how much salt and other electrolytes we have in our normal diet. However from a young teen till in my 50's, I was a very high salt user on my food. I salted everything heavily when it was put in front of me at the table. And I still didn't crust up my clothes with salt like I've seen a few others do.

I have seen a couple articles about fluid and electrolyte loss up on the NCBI website that suggested as a side note that some people actually seem to reabsorb salt and other electrolytes that were lost through sweat. So that highly suggests that the amount of electrolytes I need to replace is not going to be the same as what another person might need.

The subject of urinating periodically is probably an individual thing too for trying to gauge how you are hydrating. During the summer I can ride five and six hours and never need to go. However if I ride in the very cool days of fall, I'll have to pee every hour or two. I've always felt that it's because in the summer my body is prioritizing it's water usage for sweat.

Also, for those looking at their weight before and after, that may not be a great indicator of how well you hydrate in every circumstance. The times I let my weight get high in the winter and then started back riding again, I didn't do a lot of before and after weighing. I might have been interesting to see if there was much difference before and after while using my normal hydration habits.

I've wondered if some small portion of the 5 lbs of weight difference in my early days was just water loss as some of my fat was burned for energy since I wasn't replacing carbs through food and drink while riding back then.

Carbonfiberboy 

So you got dehydrated, didn't you? The idea is to not do too much of that. If you'd followed my advice, that wouldn't have happened. It's not far at all from your experience to a medical emergency, not far at all. If you're drinking a bottle of Gatorade every hour, you're stopping a lot. You'd be better off with a Camelbak, a liter bottle, and electrolytes.

If you're drinking 50-100 oz. of water/hour, that is shall we say, unusual. https://www.cookinglight.com/eating-...too-much-water

The gentle reader might want to read and bookmark the article linked to below, written by a rider who rode 2 Furnace Creek 508s, back to back, first the race, then a repeat the next day, done as a research project for Hammer. Those were fully supported rides, so his hydration and nutrition were not limited by logistics.
https://www.hammernutrition.com/know...u-need-to-know

Here's another article by a pretty knowledgeable guy - see his CV at the end:
https://www.roadbikerider.com/12-myt...-hydration-d3/

DrIsotope

Why does everyone always post the thing about kidney processing rate? Sweat and urine do not come from the same place, and are not the same thing. In hot conditions, the body can output significantly more sweat per hour than it can urine-- This is how I intake 10lbs of water and get home 4lbs lighter than when I left. I'm not urinating on extremely hot days because most of the fluids are being absorbed by my intestines, and coming out as sweat. I've taken in a 25oz bottle in 6 miles. According to many of these "studies," I should be dead. Things like hyponatremia and overhydration are extremely rare, especially for cyclists. The experience and approach of long-distance runners basically does not apply to cycling at all. Yeah, don't pound a 2L of water sitting on the couch. But I'm not sitting on the couch. I'm averaging ~200W at the crank, meaning I'm an 800W space heater on a day already north of 100º.

I would never, ever tell anyone a specific number or bottle or ounces to intake to remain hydrated. Everyone's needs are different. I would say to drink more than you think you need to. Because the risk of taking in an extra bottle over the course of a few hours is nothing compared to not drinking enough.

Iride01 

When your body converts it's various energy stores to energy, typically there is a certain amount of water created or freed up in the processes that go on during the conversion. So I'd always assumed there were two avenues for this uneeded water to go. Sweat or urine. Possibly the amount of water released by these processes are so miniscule that it's not significant to amount to a even a mL.

As well, I figured that the some of the water you drink goes into your blood plasma likewise your body can decide to eliminate it via sweat if cooling is needed, or by removing uneeded water from your plasma in the kidneys and send it to your bladder.

All just speculation on my part. I never got very deep into physiology in school.

Seattle Forrest

I've been known to carry a filter and refill my bottles from a creek or waterfall.

ZHVelo

I discovered - drink as much as you can, even when you don't feel 'thirsty'. I think that is probably a good guidance for almost everyone.

Especially at the start, I usually am not thirsty at all and regularly don't drink for 30-45 minutes, I guess because I drink a lot before I start, but I am pretty sure that is not ideal. I can feel it at some point. Continuously drink, and fill up at fountains or just ask for tap water to be filled in.

Hypno Toad

It's been interesting trying to fill up at public water fountains in COVID-world ... many are turned off to stop transmission. Not a fan of this policy!

Hypno Toad

I will swing back to "hot" ... as a rider that likes to have a good laugh at riders that talk about riding when it's "cold" and they are talking about 50F.

Minnesota isn't known as a hot place, but we do know how to hit some miserable temps in July. My ride last week had temps over 90F as reported by weather stations, Garmin reported temps over 100F (in the shade). Add to that our steamy summers, 97% as I rolled out. That dropped through the day, but stayed above 50% all day.

It does help to talk about what is "hot" while we talk about hydration. There are different needs/strategies for 100F in the dessert is not the same as 90F in the swamp.



I am enjoying everybody's input on this topic, BF is a great place to share info and experience! Thanks!

adamrice 

Hydration hasn't been a problem for me in the sense of "becoming dangerously dehydrated," but I know I'm not drinking as much as I should, and I wonder how much it is impairing my performance. I've been going out for 4-hour rides where the stated temperature reaches ~100°F (and you know it's hotter on the road) with a 2.5-l Camelbak. So far I've emptied it on only one of these rides. I feel like I'm drinking frequently, but clearly I'm not drinking enough.

Camelbak once sold a meter that tells you how much you're drinking (seems to be discontinued). At first I thought that seemed silly, but I can see the point.

ZHVelo

This sounds so useful. If one understood your weird units of measurement

DrIsotope

Ounces (or mils) in a bottle change depending on what people have, but there's always 60 minutes in an hour. I go off of 25oz because that's what my bottles hold.

Can't get out of the house until late today, but the high will only be ~100º, with humidity in the teens. Probably just 3 bottles for the ~3 hours, but if I get home with the 4th bottle full, better than empty. The tricky part will be the roughly 20 miles of out-in-the-open climbing with no access to services followed by ten miles of flat ground to get to a water refill. Today will be riding at a pace to manage water intake more than anything else

Iride01 

Here too. Carrying 2.5 extra pounds in my back jersey pockets is annoying. Previously I could just take some powdered mix in a small envelope or pill bottle and dump in when I refilled my bottles.

However they've turned some back on recently. Just not the one where I need it the most.

Hypno Toad

Thank you! The Hammer article is exactly the kind of information I was looking for.

Carbonfiberboy 

Try it a few times and let us know how that went. There are more good resources here: https://www.hammernutrition.com/know...tial-knowledge

As I've said before, one doesn't need to use their products, just their knowledge. In one of those publications, they mention that surprisingly a low salt diet is best for endurance in hot weather. The less salt you use in your normal diet, the less you'll sweat out and the easier it will be to keep your electrolytes in good shape. I know, seems backwards, but it works. Shouldn't be a really low salt diet, though. My wife and I try to get 3/4t of salt each every day. That's fairly easy for us to keep track of because we don't eat anything that's processed. We prepare all our own food, so we know what's in it. We pretty much never salt our food at the table, just eggs, yucky w/o salt and pepper, IMO. Oatmeal for 2 gets a scant 1/4t of salt. Etc.

clasher

It's been hot and humid here in my part of Canada, it's not "real" hot by any means, but converting to F, our highs were well into the 90s and quite humid at times. I've had good experiences with keeping a moderate water intake, I max out at a bottle an hour (~700ml), normal sized cambelbak bottles. Often I drink less than that since I like to drink a bottle of pepsi when I stop to eat, I bring sandwiches and buy a small bag of chips; eat half and take the other half with for the next stop. There's too much salt in the whole bag of chips for me, and anytime I eat the whole bag I end up drinking too much water (for me) and I don't feel as good. It doesn't seem to impact my performance too much, just discomfort so I try to avoid it. On more leisurely rides I tend to eat and drink too much due to the social nature of the stops but there hasn't been much of that this year except for a few rides with my partner when I had a big lunch instead of just a quick sandwich.

When I was tracking my diet more diligently I found I was usually eating under the RDI for sodium (3500mg I believe) so I'd guess that might be why I never get salt stains on my clothes. I don't feel like I sweat as much as other people do... I've never done a sweat test or anything like that, I doubt I ever will get into that kind of stuff. I've had good luck so far just drinking if/when I get thirsty and not drinking more than I can absorb. I don't like drinking to a rule or a timer since it tends to be too much for me, but for folks that tend to drink too little I think it's a good idea to try that instead if paying attention to thirst doesn't work for you.

Couple weeks ago, I did 220K in 9:31 total time, with 3 ~20 minute stops for food/water, and two flats ate up another ~30 minutes. I lost 8lbs on that ride but it was one of my quickest times overall. I felt great afterwards too. I averaged 200W over the 7:51 I was on the bike according to rwgps and my powertap hub. I know it's not a massive effort or the fastest ride but it's a pretty steady 75% of my ftp for 8 hrs.

Hypno Toad

I continue to track my sweat rate on rides at different temps and different level of effort ... but I realized with my allergies, this calculation doesn't consider the amount of fluid lost to snot rockets and loogies I guess it's time to start riding with a spittoon to include in my measurements and calculations

clasher

LOL don't forget the water that comes out in your breath, as well as all the water in turds.

Hypno Toad

Not on topic, but talking about hot and humid ... anybody living in the corn belt knows about 'corn sweat'. Kinda on topic since we are talking about what is 'hot' weather for riding, temp doesn't mean much without factoring the humidity. As crops mature, it gets more miserable around here.

"Corn is likely the most prolific contributor. The National Weather Service in Des Moines, Iowa, recently noted that mature Iowa corn pumps out 49 to 56 billion gallons of water into the atmosphere each day, which can add , pushing heat index values to 110 degrees or higher."
Source: https://www.mprnews.org/story/2016/0...ame-corn-crops