I went out for a reasonably hard ride today - a little over 2 hours solo and I pushed the pace pretty strong but didn't really 'max out'. No long climbs but constant short up's and down's.

It was a low humidity day (by east coast standards) with temps in the low to mid 80's. For cycling purposes it was pretty comfortable. I weighed myself and my water bottles before/after the ride (didn't eat anything and no electrolytes, BTW). When I weighed myself and my water bottles immediately after the ride, 7.8 pounds (of water, I assume) was gone.

So let's say I tend to lose 4 pounds of water per hour. If you are planning on something like a hot weather century, that is a lot of water to deal with. I'm curious as to how others deal with the problem on long training rides, century rides (where at least there might be some support), etc. I would assume that if it were hotter than today my 4 pounds/hour could/would go up - maybe a good bit.

FWIW, I tend to be pretty tolerant of dehydration. I only consumed one pound of water (2/3 of a 22 oz water bottle) on this ride with no apparent ill effects. I felt fine after the ride (but I surely drank a ton of various non-alcoholic liquids). And my average power output the last 30 minutes was 6 watts higher than the average for the ride. So I wasn't suffering (yet). But I know from my running days that I have my limits here.

I'm just wondering what other folk's "sweat rates" are and how folks go about replacing 4+ pounds of water per hour on longer rides.

Thanks.

dave

I went on a 41 mile rid, temps in the mid 70s with some humidity.... I refilled my 20oz bottle 2 times.

If you wait till your thirsty, it's already too late.

Don't worry about the weight of the water bottles. All that really matters is how much weight you lost. A pound = a pint is pretty close.

I usually do about one 24 oz water bottle per hour if it's warm and humid. More if it's hot. I once did a double century ride which reach 95 F degrees and I drank gallons of fluids.

One thing that does help is sports drinks. The amount of sodium and other electrolytes in them help use the water quicker. Plus the sugar is a good source of fuel. Also drinking a lot of plain water can be dangerous as it can cause water intoxication (AKA Hyponatremia) which can be dangerous and even deadly The electrolytes in sports drinks help prevent this condition.

If it's reasonable temperature, I drink about a bottle (20 oz) per hour. If it's hot (upper 80s, 90+) I can drink more than 2 per hour and still be thirsty after a 4 hour ride. If I'm not racing, easy, just stop and refill. I get my calories and electrolytes from my drink mix - 3 bottles of infinit nutrition mix is good for 4 hours, or more if I'm properly loaded on carbs. For road races, which can be 3-4 hours I just hydrate a lot, then bring 3 bottles. If there aren't water handups and it's hot I'll be pretty dehydrated afterwards, but not so much that I lose power during the race.

I did a similar 2 hr ride yesterday and drank maybe 16-20 oz during the ride. I was probably down about 3-4 lbs but didn't weigh myself beforehand so I don't have precise numbers. I know from experience I can go hard for a couple of hours with no water and not suffer any ill effects. I weigh around 165lbs and I think you can lose 3-4% of bodyweight without any impact on performance. You might even be a little faster if there are hills involved.

Just remember that if you ride several days in a row it's good to drink enough during each ride. Even if you can do one ride on little water/calories, it's easier to replenish and keep the hydration/glycogen levels up for the next day if you get enough during the ride.

Never calculated a sweat rate. Probably changes quite a big depending on multiple factors. I can't carry enough fluid for even a 40 mile ride so depend on convenience stores for rest stops, fluids and fluid relief. I carry a DL, debit card and cash in a thin case that I tuck under my shorts on top of my quad. Usuall ride with my GF so it's always my treat LOL.

Agree with respect to glycogen if you're doing back to back big rides but water? I don't think it's that difficult to replenish provided you have sufficient sodium intake.

Maybe not. I just drink too much beer and need all the water I can get lol

The latest studies show two things contradicting old beliefs. One is you don't have to replace all fluids lost during exercise. In fact it can even be dangerous carried to extremes. The other is drink when you're thirsty as a valid gauge.

Not sure all weight loss is due to water.. Burning calories is a phrase I've come across, and water has zero of them.

Each gram of carbohydrate stored in your body requires 3-4 gms of water. When you burn those carbs the water is also released. That's one reason dieters often find themselves shedding a lot of weight when they restrict caloric input, their glycogen stores along with the associated water is reduced giving the illusion of rapid weight loss.

human fat has 3500 calories per lb, not sure about glycogen....so 8 hours riding could in theory burn 1 lb of fat or so. Sounds like the body can store just over 1 lb of glycogen on average from a quick google anyway, and you can only access what is in cycling muscles.

Lots of options here. If you ride in areas with businesses, you can buy water or ask restaurants to fill your bottles -- I've never had one refuse. If you ride in rural areas with people but not businesses, you can fill your water from a church spigot (always works) or stop by a house and ask if you can fill from the spigot. The vast majority will fill from the tap. I think I've only had one person ever not let me have any water at all in the past 30 years. If you are in areas where there are not even homes, you can plant water in strategic locations by the side of the road.

Don't forget electrolytes if you're sweating that much. It can be a big deal.

BTW, losing 7.8 lbs in two hours is insane. 4 lbs/hr with temps in the 80's sounds high -- that's two quarts per hour. More of a hot desert type of rate loss. Hopefully, there was an issue with your scale or some other factor was at play but it's likely you were dehydrated. Don't get that far behind on water -- seriously. You go from riding along thinking you're fine to passing out so fast you won't even realize what's going on. You will have more fun and put out better power if you take care of yourself.

I will probably be paying more attention to this down the road, but I suspect that this is about right. I am an ex-runner and have raced two marathons (a LONG time ago) in pretty much identical conditions. In both of them (finishing times a bit under 3 hours) I lost about 12 pounds (I am unable to run and drink, but I can pedal and drink) and was in serious trouble at the end.

Since I did consume about 1 pound of water my net loss was under 7 pounds. I'm not saying that this is a good idea, but if I was dehydrated I felt no symptoms at all. But I suspect that I was close to 'the edge' here (just a guess).

dave

I don't worry about water on short rides like that. As you saw, you didn't need to, either. On long rides, there's a limit of about 1 liter/hour being all you can get to cross the stomach wall. Even that much may require training for some people. As most folks above said, about 1 bottle/hour is normal. However, it's possible to lose a lot more than that. So on a long ride, here's what I do: I drink to thirst. If I don't think I'm as thirsty as I should be, I take one or more Endurolytes, which stimulate thirst and provide electrolytes to match the water.

I have a maxim which is that I should pee about every 3 hours. If after 3 hours I can't pee, I sit in the shade somewhere, drink water and take Endurolytes until I can, then go on. This sometimes takes 20 minutes, but it's better than heat stroke.

A good sign of damaging dehydration is increased heart rate. I've seen my resting HR go up to 130 on a long, hot ride with a lot of climbing. Sit in the shade and drink until it goes back down to 100. My morning resting HR is ~46. Around here, another good sign is having a light sweat on the forearms. Lack of moisture is a bad sign. However I understand that in very low humidity this is not helpful.

Lance once lost 13 lbs. on a hot 50 mile TT IIRC. He was toast then and the next day.

I think your assuming way too much.

Your percentage of hydration is not static... although people to tend to have average hydration levels... they are individual and can vary greatly. As an example... I just checked my hydration/water percentage (I have a scale that does that) and I am currently 45.2% water. However... that can easily be as high as 55%. Depending on body weight... a fully hydrated body apposed to a recently sweaty body could easily vary a few pounds.

This input/output weighing doesn't really provide much information.... particularly in events that only last very limited times (2 hours) and where consummation isn't well controlled (like drinking: a ton of various non-alcoholic liquids).

Dehydrating isn't weight loss... and it is dangerous. There are plenty of posts here about how to stay proper hydrated. I'd read them over and give up on weighing water bottles.

if "a pint's a pound the world around" is true (and it think it is) then it's probably not possible to replenish four pounds of water per hour. maybe two.

BTW, according to some, a 10% loss of water weight will result in a near death experience. we are about 60% water (60 pints per 100 pounds of body weight in males). so a 100 lb person that's running a 6 pint water deficit won't be feeling too good. and a 200 pounder could afford to lose 12 pints before feeling the same effects, on average.

Re: The Bold Stuff

I'm not sure that I understand here. I was just trying to get a handle on my personal water consumption (I perceive myself to be a heavy sweating type - possibly outside most norms). So how does weighing yourself before/after exercise not 'provide much information'? I guess there is a whole bunch of 02 in and CO2 out going on. Is that the point/issue? This seems to me to be exactly where one would start if a hot weather century ride was likely later this year. Can you elaborate?

BTW, the 'tons of various non-alcoholic liquids' was totally outside the measurement system and done after all exercising and weighing was complete (and was only mentioned as a way of saying that, while I was not feeling much thirst during the ride, I certainly was 10 minutes after the ride).

Thanks.

dave

IMHO I'd worry more about whether you are a salty sweater than the other stuff. If you are you need more electrolytes, and no matter how much straight water you drink you may not hydrate properly.

Weighing yourself.... only gives you weight. It does NOT provide you with your hydration level. It just doesn't provide much information.

Thanks - I understand. I was simply going after an assessment of 'how much water I was losing'. I'm still assuming that (understanding that electrolyte content remains a guess), what I measured is a reasonable indicator of what I lost in terms of water.

dave

Did another experiment today on a 2.5 hour ride. Again I was just focused on water loss (not electrolytes - a different question). And I DON'T CARE how much water bottles weigh, BTW (not at all the point).

Me loaded up (including two full 22 oz. water bottles, shoes, helmet, clothes, etc) was 165.2 pounds. Me after the ride with all the same stuff (except one water bottle was empty) was 154.3 pounds. So 4 pounds/hour water loss rate (high 80's, not humid by south eastern US standards) is a decent planning assumption here it would seem.

So assume the following.

• 5.5 hour century -> 22 pounds of water
• Pre-hydrate 2 pounds (really don't know what is reasonable here)
• Consume a 22 oz water bottle every 45 minutes (for 5 hours - the water taken in the last 30 minutes will really only help recovery). This is at the edge of how much water your body can absorb during exercise, from what I understand.

The above seems to me to be reasonable (validity of the assumptions plus do-ability of the hydration, assuming some pretty good support on the route). And this yields a net loss of around 10.5 pounds which is a little under 7% body weight and this is a total NET water loss in the range of what I have tolerated in the past, including today. I could consume more water, but I'm not sure that I could absorb it (from what I know).

So I guess that this can be done, but I will have to train myself to consume this much fluid. I haven't done anything in a while over 3 hours and even those rides have typically ended at dusk with lower temps.

Electrolytes - a different question and it is my experience that the content of your sweat changes dramatically with heat training.

FWIW.

dave

I'll just add in the data point that I did from a recent supported century. Route was 100mi (6500 ft elevation) with 5 stops. Weather was mild, sunny with a light wind. Starting temp was about 55 with a high in the low 80s.

Between rest stops I would drink 8-16oz water (22 oz bottle refilled at each stop). At each of the stops I would drink ~8oz of electrolyte fluid, plus ~150 calories of mixed sugars with another 100 cal of some fat and protein. After the last stop there was a significant climb (~1 mi at 12%), I tucked a can of Coke in my jersey as an emergency ration. Never needed it.

Total time was about 7 hrs pedalling, about 8.5 hours total. Total fluid intake was probably something like 100 oz.

All of the stuff required for that century could potentially have been carried in a Camelbak or pannier. Realistically, there's tons of re-supply options out there. Starbucks or a gas station can be solid resupply points. Around here the barristas know the cyclists come for rest stops and will refill bottles (with ice!). I make it a point to always buy a coffee, snack or leave and/or leave a decent $1-2 tip.

The key is planning a route to know where re-supply points are. Make sure you carry enough food/water to make it to the next re-supply even under the worst conditions. I carried 1 bottle for the supported century because the stops were plentiful and I knew the food was good.

On my last group ride (40 miles) I drained four 24 oz bottles, I could have used at least one more. There's no refill point on the ride, so what you leave with is what you get. The first time I did the ride I had a bottle and a half, and was out less than halfway in. By the time I got home I thought I was going to pass out, since I'd stopped sweating long ago. It took me a few days to get completely hydrated again. Most of the other riders had two bottles and didn't run out of water, but I'll sweat sitting still on a cool day.