"Routine Dehydration"
 

I am a heavy sweater type guy where 4 pounds of water lost per hour is not unusual at all for me. My ride yesterday was typical other than the fact that I carefully weighed myself (no clothing) immediately before and after the ride. It started at 10:00 a.m. and was planned at 2 hours to no more than 2:15. Temps at the start were in the 80's and about 90 when I stopped 2:15 hours (and about 40 miles) later. I took 44 ounces of water as a backup but, as is my norm for rides of this length, just didn't bother to drink anything. If this had any kind of meaningful effect on my performance I was not aware of it. And as is typical for me on rides like this I felt no particular need for water (during the ride - 5 minutes after it ends is different). FWIW, had the ride been much longer then both water and nutrients would have been an issue.

And when I got on the scales immediately after the ride (again no clothing) I had lost 10.5 of the 163 pounds that I started with. This is just normal for me and I do it all the time. Conventional thinking is (I think) that this is dangerous. Maybe it is but I really have done this hundreds of times.

Anyone else out there do this kind of thing on a routine basis?

dave

ps. And do note that this is roughly the outside edge of my ability to easily ride without water or nutrition (and as I said the water is carried as a backup). I can get home 'on a bonk' but dehydration much past this point would be an issue.

I could lose 5 or 6 pounds in a couple of hours when I weighed 163. Now I weigh about 143 and don't lose more than a pound or so under the same conditions.

To me that means that you sweat 5 to 6x as much at 143 vs. 163. That seems surprising. I have weighed as little as 153 but got pretty tired of trying to convince my friends that I was not seriously ill :)

dave

I don't know if it does or doesn't, but I've always imagined that when you lose water through sweat and don't replace it as you can, then some of that sweat is the water in your blood plasma. Maybe not.

But if it is, then your blood plasma will be getting thicker and that seems like it'd be hard on your heart. Might make it wear out quicker.

I used to lose five pounds of water back before I learned to hydrate adequately. My 170 lb self seldom changes by a pound or so on even a 60 mile ride. On my 1:24 hr:min ride for 22 miles today I drank 40 of my 48 ounces before getting home. Didn't have to force any of it. It was only 92ºF or I would have drank more.

Having just come off the golf course (walking) on a very humid day, it doesn't feel like I sweat any less.

I had the same problem when I dropped into the 140s. People constantly asked me if I was ill.

I had always lost water weight playing golf, but it came right back on. I started riding again about 10 years ago after a 30 year break and had the same experience. But after a couple of months the pounds didn't all quite come back. After a couple more months, I was down about 20 pounds. Hadn't been at that weight since I was 20. With all the comments it was a bit worried, but my doctor said I seemed fine and I stabilized there.

Personal best: 64 miles in 3h30m (moving,) average ride temperature 102º, high temp 113º; during ride, drank seven 25oz water bottles, plus roughly 32oz water at stops that never made it into the bottles, for a total of 207fl/oz. This means I drank just about 13.5lbs of water. I drank an entire 25oz bottle in the final 10 minutes. Stepping on the scale post-ride, I had lost a bit over 7 pounds, meaning I put out almost 21lbs of sweat. Nearly 6lbs per hour.

I think I'm perpetually dehydrated, despite taking in well over a gallon on a typical summer day, not including water during my daily ride. Hot days can routinely exceed 2 gallons. As such, my weight can fluctuate 8-10lbs over the course of a day-- though I am a fair bit bigger than everyone else in here, around 215lbs.

Different people seem to have different hydration needs. A couple of friends often carry only one bottle on rides up to 50 miles, although we'll often stop at a convenience store around 30 miles and they'll refill.

I can't do that. Well, I *can*, but I'll feel terrible. Not worth the risk, especially in summer. For some reason my trickiest time of year is early spring. If I'm not careful I'll neglect to drink enough on the first warm days and need to pull over with stomach cramps and wait about 15 minutes after drinking water with electrolytes for the cramps to ease.

I go through a 24 oz bottle every hour and could drink more if I carried it. In cooler weather (under 80F) I might take 90 minutes to 2 hours to finish a bottle. In summer I'll go through a bottle in about 45 minutes. And I almost never need to stop to urinate, unless there's a beer stop. As soon as I drink one beer, as the saying goes, once you break the seal the flow never stops. So I rarely drink beer other than after a casual group ride.

And as soon as I get home I go through another pint to quart of fluids within an hour.

When I was an amateur boxer it was pretty common for boxers to try to make weight by sweating it off just before weigh-in. From my observations fighters who had to sweat off much to make weight rarely did well in the ring. I usually preferred to lose my weight early in the season, get accustomed to it, and keep it off. I'd sometimes come in lighter than the weight cutoff but felt strong and did fine.

In similar weather to O.P., I'll sweat a similar amount. However, I try not to lose the weight that quickly. It's not as much a problem on a single short 2 hour ride, but when I ride longer or do daily rides like that, I can kick myself into heat exhaustion (or worse). Did that earlier this month. It's not a good idea.

I've found that it's hard for me to ingest more than about a quart an hour (aka 1 liter, aka 2 pounds, aka 1 kg). I try to train myself to drink as much as I can. Setting my GPS to beep every 15 minutes to remind me to drink 8 ounces helps me spread drinking out during the ride without triggering dumping syndrome -- that's REALLY not fun during a bike ride! That drops my weight loss to only 2 pounds per hour -- I can ride twice as long before I run into trouble than if I didn't drink during the ride!

As a cardiac survivor, I'm supposed to watch my salt intake. Riding 150-200 miles a week in the heat, pass me the salt shaker at the table. My wife is the one in the family who sees the result of bloating from too much salt -- I just feel better when I can drink enough fluids to replenish sweat loss and keep them in. (And my cardiologist, the cyclist, agrees with me.)

This time of year, I don't really know what I weigh. I'm pretty sure the low end, 15 pounds below what I weighed a week later, isn't my "true weight." So instead of a stake in the sand, I've mentally laid down a stick 5 pounds long that's about right.

This study https://pubmed.ncbi.nlm.nih.gov/23121348/
relates what is now well-accepted gospel - some dehydration is beneficial to performance, but that limit is somewhere around 3%. IMO the OP should experiment with drinking strategies to produce that 3% result, just to get the feel of it if nothing else. So that would be per pdlamb and many other sources, 1 liter/hour, which is the normal limit to push across the stomach wall. As the linked study says, you want to drink to thirst, which will mean consuming sufficient electrolytes say an hour before the ride's start, and continuing for the duration of the ride, to create a constant slight sensation of thirst, only briefly allayed immediately after drinking. Carry liter bottles, Zefal Magnum is the only one I know of and is what I use. By constantly being slightly thirsty one is assured of having the optimal blood electrolyte levels. If one has not been thirsty, one has no clue. The OP wasn't particularly thirsty on this comparatively short ride because his blood levels were in balance. Had he drunk only water, they would no longer have been so.

I was a "routine dehydrator" for many years, both biking and kayaking (where you need your hands all the time, even harder to drink while moving), and hiking for that matter. Bonked once or twice under extreme circumstances where everyone else was, too.

About 15 years ago (I was 48, so decades of ignoring hydration advice) while mowing the lawn I starting feel nauseous with back pain. To make a long painful story, turns out I had a kidney stone. The major recommendation from the doctor was "stay hydrated." It was a very painful experience so I followed the advice for a while but fell off the wagon - and the next kidney stone hit while I was on a plane flying cross country and was even more painful.

I have been a faithful hydrator since then - and no more kidney stones.

One way to imagine the pain: at the emergency room, the female nurses and female doctor all said the same thing: "Ha - now you have an idea of what giving birth feels like!"

Drink those water bottles while you ride!

jpescatore That is very interesting and useful. Thanks. dave

Kind of targeting 3% seems reasonable. And I have long been aware of the fact that I sweat at about 2x the rate that I can absorb water. But I don't do the regular really long rides that seem your norm, so that is rarely an issue for me. Of course I can absorb 100% of the water that I consume when I don't drink anything :)

dave

It's OK - until it isn't.

It would be interesting to know what is going on with your blood pressure after one these exercise sessions. Checking your heart for arrhythmia while "down 10lbs" of fluids would be useful as well. Eventually you'll notice some problems if you continue to use this "routine hydration" as normal later in life.

I hit age 71 later this year. How late in life do I have to wait here :):)

dave

ps. I am not arguing that you are necessarily wrong. I really don't know. I do however know from my serious running days back about 35-40 years ago that much more fluid loss than this was a SERIOUS performance problem. I did that twice and that was the last time (I thought it was a pace problem the first time).

Same, here.

I'm 200lbs
I take 4 x 24oz bottles and drink them all on a 45mile ride. I lose 5 lbs in total weight comparing pre and post...so that tells me the 100oz water plus my 5lbs = 10-11 pounds total loss....glad i know someone else like me!!

JAG

carbonfiberboy is onto it.

If it affects plasma volume, it affects power. Without even knowing any better, I pretty much follow what he posted above.

Well, that is extraordinary.

One aspect of athletic performance that usually changes with aging - is the ability to tolerate electrolyte changes - in other words most people usually cramp up more easily. I experience this as "night cramping" if I workout and don't completely re hydrate. When I was young - I had a lot more lee way and could run around on "empty" - and still not cramp.

I guess you are special.

Having been active all my life and always a heavy sweating type, my guess is that my system simply adjusted to being dehydrated on a regular basis.

I do on rare occasions suffer from cramps, but they don't seem to be associated with dehydration. I have only encountered them a couple times on a bike, and I was not badly dehydrated in any of those cases. However I do suffer from idiopathic vastus medialis (inner thigh) cramps that will just show up in bed while sleeping, while sitting in my easy chair, driving my car, etc. Many of these have been during the cool season (or even during periods of no workouts). But ALMOST never on a bike. Go figure.

dave

ps. I once lost around 13-14 pounds in a marathon. My legs basically quit working but I never cramped. But that experience got my attention in a serious way.