Am I completely insane to run BTA hydration on my gravel set up?

My A-Race next year is Gravel Worlds. For those that don’t know, Gravel Worlds is 150 mile gravel race around Lincoln, NE. The course changes every year, but it’s always involves non-stop rolling hills. The course always has roughly 10,000 ft of total climbing every year, but it’s broken up in endless 50-100 vertical feet chunks. The difference in elevation between the highest and lowest points on the course will be about 300 feet.

The gravel is pea sized and, if you can find the tire tracks, its not really that far off from asphalt:


My primary goal is sub-8 hours…which equates to about 18-19 mph average, but real speed on the course is probably slightly faster due to time off the bike. A lot of this will depend, of course, on the conditions of the day. However, at a moving speed close to 20mph, I think aerodynamics will still matter A LOT–according to the Flo guys, the difference between a Open Pro and their Flo 60 is almost 9 minutes at 20 MPH over an Ironman bike course.

There is no outside support permitted (other than neutral support at the checkpoints). Two mandatory checkpoints and other optional checkpoints along the way. I’d like to be able to carry enough water to only need to stop at the mandatory checkpoints.

Pretty much everyone will be using aero bars and I will use them too. I expect at some point I’ll get spit out the back of the lead group and getting stuck out in the wind for 50 miles by yourself on the plains is no fun for anyone and much less so without aero bars.

So here are my thoughts:

  1. It’s pretty well established that, in the time trial position, having hydration between your arms is faster than pretty much any alternative. I have no idea if this holds true in a normal road bike position.
  2. I’d like to have enough fluid on board for 3 hours total per checkpoint. 24oz/hr puts the total at 72oz. That’s kind of cutting it close, but there should be enough gas stations/optional checkpoints to refill if I get in a jam and need more water.
  3. Based on this, my hydration setup could then look like one of the following:
    a. DREAM AERO SETUP: 24 oz BTA + 2 24oz bottles behind the seat (lots of testing would be need to ensure I’m not ejecting bottles left and right)
    b. 24 oz BTA + 50 oz USWE hydration pack.
    c. 24 oz BTA + 2 24 oz bottles in frame

I would really love to get some data on (a) how much of my time needs to actually be spent in the aero bars to make the BTA “worth it” and (b) what is faster between the hydration pack and bottles in frame options. I’m also wondering what kind of impact on handling a BTA set up would have.

I’m planning on picking off a lot of the other low-hanging fruit as well: aero road helmet, skin suit, deep-ish section wheels, fast tubeless tires, trainerroad subscription. I might even rock shoe covers if its not too hot :joy:

I realize that doing this will make me look like a HUGE dork, but I don’t really care as long as its fast.

Is there anything I’m seriously overlooking here?

FYI, since nobody said I shouldn’t do this I’m going to go for it and see what happens.

I have a couple of tune up races before my A race so I’ll give it a go and can ditch it if it doesn’t work.


Seems like a fine idea to me. I say use it if it is within the rules.

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I appreciate the “Other Chad” stamp of approval. I’ll make sure to report my findings.

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For whatever my opinion is worth… :stuck_out_tongue:

If possible, I’d love to hear about your experience. I am planning a gravel focus this season, and hearing about these larger events is fun for me since I’m a bit far from those ones.

I would be happy to do so. I will probably revisit this thread once I get my set up dialed in.

I would like to find some time next spring do some chung method aero testing on the various setups discussed above.

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I don’t have data, but my experience is that if I have aerobars and a BTA bottle, but I only use it some of the time… I am a little faster than if I had neither and couldn’t ride in aero at all. So you probably aren’t costing yourself time by having it and not using it.

Drinking from a BTA setup while you’re up on the hoods is another matter. It doesn’t work very well. As for handling, I have never noticed a difference with a bottle there vs. not.

I know people in the triathlon world who have tried hydration packs, and they seem to be generally uncomfortable and warm up the liquid faster. The scheme the TR crew used at Leadville, with a support team providing fresh cold hydration packs, is probably the best way to make them work for the long haul.

For bottles behind the seat, look to tridorks for what works: XLAB Gorilla Cage and TriRig Kappa cages.

However, I sort of feel like the relative aero cost of bottles on the down tube / seat tube are not that big a deal. They aren’t ideal, maybe, but they aren’t going to make nearly as big a difference as how much time you spend in an aero position, whether you have to soft pedal while digging a bottle out from behind your saddle, how much time you lose to ejecting bottles behind you…


These are some good points. If I can get the BTA squared away then I can play around with my options. I think the aero testing will be crucial to make an educated decision on whether the time savings are worth it. Additionally, I’ll have a few warm up races to dial all of this stuff in. I’d rather eject a bottle at one of those races and know that it won’t work.

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I did DK200 this past year with clip-on aero bars and have some experience that might carry over. It sounds like DK has much rougher gravel than your event, so YMMV. DK has 3 rest stops, roughly every 50 miles, and riders are self-supported so one needs to carry enough water for ~3.5-4 hrs between refills. It also can be VERY windy and VERY hot. This past year was both: >100F for several hours mid-day, and 25+ mph block headwind for most of the second hundred miles.

Riders frequently struggle with dehydration at this event and I really wanted to avoid this. I’m a heavy sweater, so I carried 2@ 1 liter bottles of Skratch, 1@ 750ml bottle of a different flavor Skratch, a nicely fitted frame pack with a 2.5 liter bladder filled with water and a hose with bite valve run up BTA. So, kind of like what you’re thinking about, but turned up to 11.

In a nutshell: this was a great way to go. Hydration packs are hot and not aero. The course was strewn with literally hundreds of bottles that had been ejected from saddle-mounted holders (with the bonus being that their owners didn’t know they suddenly had no water until miles later when they went to take a drink, uh-oh). I spent a ton of time in my aero bars and being able to sip water without breaking position was huge while clawing upwind.

As I said, I understand your event is a bit different so you may not need to go to the extremes that I did. My only concern, though, is that you may not be carrying enough hydration on the bike if you “only” have just over 2l and you’re trying to go 3 hours at a stretch, at race pace, possibly in some serious heat. Maybe that would be sufficient for a single 3 hour leg, but I’d be concerned that your third leg could find you dehydrated. My experience at DK was that the first 100 miles was pretty easy and then people (myself included) started to blow up left and right–mostly, I suspect, from dehydration. I’ve since measured my sweat rate and it can exceed 2l/hour, which blew my mind. So even if I’m drinking 1l/hr, which is hard to do, I’m still running a deficit of 1l/hr or more. No prob for a few hours but for a very long event… watch out.

Sorry, I hope I don’t sound too mansplain-y here :wink: It’s my longwinded way of saying 1) Yes, BTA hydration is smart, and 2) If possible, I think it’s better to approach it by measuring what your body needs rather than what’s convenient to carry. I hope you’ll update here in the forum–I’ve yet to settle on a hydration approach for ultra events that I’m completely confident in.


Thank you for sharing your experiences. I’m also encouraged to hear that BTA worked for you.

I would like to point a couple things out though.

  1. This race is on home turf, so I’m definitely aware of the demands that the heat could potentially put on me. Weather in this part of the country is a real crap shoot, though. It could be 100F with unbelievable humidity or it could just as easily be 70F. I’ll really need to be prepared for everything.

  2. My hypothetical hydration set ups listed above were based on the maximum volume of fluid I can take down in an hour. I believe the upper limit of liquid the stomach can process in a hour is about 800ml. I just can’t imagine drinking more than 24oz of fluid in an hour and still being able to eat what I’ll need to eat over the course of the day. I also religiously weigh myself before and after every ride so I have a pretty good handle on that front.

I’ll probably go with Skratch to help with maximize absorption and keep my electrolytes somewhat in check.

Unfortunately, you’re never going to be able to completely replace the fluid you lose, especially for a big endurance event like this. I think a big key is to focus on your hydration before the event. I think between carb loading and taking in some hyper hydration drinks, I should hopefully be carrying a lot more water weight than normal going into race day.

Roger that. Ultra events like this are about so much more than “just” riding your bike, eh? Looking forward to seeing your final setup and hearing about your event. Good luck!

I think it’s akin to an Ironman. It’s an eating and drinking contest more than anything.

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I can’t find studies to back this up, but my experience is a bit higher. Doing the Cozumel 70.3 this year (hot, humid, but water stations about every 11km/7mi on the bike course), I went through one 28oz bottle, two 24oz bottles, and three 20oz (I think?) Gatorade bottles I picked up along the way, for about 1.3L/hr. Of course as soon as I got off the bike I started running, and I did not feel bloated or sloshy at that point, leading me to believe I was not significantly overdoing the amount of liquid I consumed.

That said… my point isn’t to say you should plan on that volume, but that you shouldn’t see some particular number as a maximum written in stone. Experiment in training, and in particular, test your limits. Plan on having a couple of rides where you take in so much hydration you know you’ve hit your limit (only actually perform one where you hit that point… but the first time you might find you didn’t hit your limit).

Here are a couple resources:


Fluid intake is a balance between fluid deficit, which has been shown in laboratory studies to result in a decrease in work capacity and to contribute to the development of hyperthermia, and fluid overload that can result in exercise-associated hyponatremia (EAH) (11,13,24,34,69,73,81). In 1969, Wyndham and Strydom published a report on runners who ran Sugar’s Marathon in Johannesburg, South Africa, on two fall days in 1969, which helped shape fluid consumption recommendations for the next 30 years (18,101). In the study, there was a linear correlation between weight loss and increasing rectal temperatures at the finish of the marathon. The authors noted a rise in temperature to >102°F occurred more frequently in individuals with >3% loss in body weight and felt the increase in temperature could lead to heat stroke (although none of the runners developed heat stroke). They concluded that thirst was not a good gauge of hydration status and stated, “The ideal regimen of water drinking is to take about 300 ml every 20 minutes or so. This should start right at the beginning of the race.” Of interest is that the runner with the greatest degree of dehydration and rectal temperature won the race on both days.

Results from more recent studies have refuted Wyndham and Strydom’s concerns that thirst is not a good indicator for hydration status and that >3% weight loss from evaporation of sweat will result in heat stroke. Looking at competitors in the South African Ironman, Sharwood et al. (87) showed that pre- to postrace changes in body weight were not related to postrace rectal temperatures. Some of the ultraendurance triathletes they studied sustained a 6% loss in body weight without a resultant increase in medical problems (87,88). In addition, body weight loss of 3% in the Ironman race did not lead to thermoregulatory failure (64).

In half-marathon runners and ultramarathoners, body mass alone may not be an accurate indicator of hydration status. Tam et al. (94) looked at runners of 21.1- and 52-km races and found they lost body mass (from a combination of substrate utilization, sweat evaporation, and insensible fluid loss) but overall gained total body water while preserving serum sodium and potassium and only had a small change in serum osmolality. Despite not drinking as much as sweat losses, they attributed the increase in total body water from release of water stored with glycogen that was released during muscle glycogen metabolism and possibly from fluid stores in the GI tract. Kao et al . (56) evaluated body weight changes before, at 4-h intervals during, and immediately after 12- and 24-h ultramarathons and found a positive correlation between weight loss and performance in the 24-h race.

Athletes should have a basic hydration plan prior to entering competition that they have developed and tested during their training sessions. The 2002 International Marathon Medical Directors Association guidelines, although targeted at marathon runners, are a good starting point for athletes in ultraendurance events (68). These advise that marathon runners drink approximately 400 to 800 mL·h−1, with increased rates for the faster, heavier runners, competing in warm conditions, but no more than 800 mL·h−1. Although faster competitors often finish with more significant dehydration, they often have greater experience and may be able to safely tolerate a higher degree of dehydration without suffering negative medical consequences (68,74,101). Pre- and postworkout weights can help athletes assess fluid needs for specific training loads, and monitoring urine color (aim for light yellow) and frequency can help athletes predict needs during events. On race day, athletes need to be flexible in their fluid plans to account for race day environmental conditions.


Historically, exercise-induced heat stroke was believed to be solely attributed to dehydration due to inhibited sweat evaporation secondary to decreased cutaneous blood flow with inhibited energy dissipation through evaporation. In addition, laboratory and dessert studies (not studies in actual racers) showed high fatigability in individuals with >2% dehydration thought to be due to decreased cardiac output — the rate limiting step for oxygen delivery to working muscles in most athletes (37).

Wyndham and Strydom’s (54) landmark study in 1969 evaluated marathon runners in race conditions. Several runners including the winner had dangerously high rectal temperature, according to the authors, and the rectal temperature correlated with the degree of dehydration. They interpreted their data as a warning to drink more during exercise instead of a possible alternative theory that those who can sustain greater dehydration levels and higher rectal temperatures will win the race.

For years to follow, athletes were told that thirst was not a reliable indicator of hydration status, and they needed to drink continuously. Consequently, hundreds of athletes imbibed high quantities of fluids before, during, and after racing resulting in excessive free fluid lowering serum sodium concentration with resultant exercise-associated hyponatremia (EAH). Exertional hyponatremia can result in pulmonary edema and, in more severe cases, brain swelling, and death (24).

In 2003, Dr. Tim Noakes and the International Marathon Medical Directors Association presented a hydration plan with a different interpretation of the evidence (37). They said runners (and we can extrapolate to triathletes) should drink ad libitum — as thirst dictates. They recommended an approximate guide of 400 to 800 mL·h−1 with increased rates for faster or larger athletes especially in warm environmental conditions and less fluids for smaller, slower athletes or those in colder environmental condition.

While severe dehydration with exercise can result in an increase in core body temperature, the heat burden is based on the athlete’s metabolic rate and can be lowered by slowing pace. There has been no compelling evidence to suggest a change in these well thought out recommendations.

More recent studies have only added support for the ad libitum fluid plan. Beis et al. (5) used retrospective video analysis of 10 elite marathoners in 13 city marathons evaluating footage from the cameraman on a motorcycle following the lead pack and showed that while a variation of fluid intake occurred, most stayed within the 400 to 800 mL·h−1 recommendation, and one of the winners had almost 10% dehydration. Wall et al. (51) had 10 well-trained cyclists perform a 2-h laboratory submaximum training session of biking and walking to produce 3% dehydration. Afterward, the athletes received blinded postexercise intravenous rehydration to return them to euhydration, 2%, or 3% dehydration. Subsequently, a 25-km time trial with a fan to simulate environmental cycling conditions did not result in a significant difference between the groups in time to completion, wattage produced, or rating of perceived exertion.

Currently, competitive cyclists are experimenting with controlled dehydration while climbing on the bike to lower overall body weight in an effort to lower wattage/kg ratio but not enough to decrease cardiac output. This strategy could provide some benefits for triathletes competing on hilly courses provided they could still handle the postbike run.

We advise triathletes to determine their individual hydration plan by initially starting with 400 to 800 mL·h−1 and listening to their thirst. Additional information on fluid needs can be gained by following the position article on exercise and fluid replacement (44) and obtaining preexercise and postexercise weights to determine sweat loss for individual workouts in specific ambient conditions to a get a sense of one’s individual sweat rate. In more experienced triathletes, the plan can be altered once the athlete determines in what hydration state he or she functions best. Like all plans, it will need to be altered based on environmental and personal conditions on each individual day.

Okay, thank you. I’ll point out that that maximum of 800mL/hr seems in both citations to be centered around runners, with the second one extrapolating with no change to triathletes (and then by you, to pure cycling). I think cycling lends itself to processing higher volumes of liquid into the blood than running does.

Why do you think that?

One of the advantages of training triathlon is that we actually experience running and cycling :blush:

So my experience and the experience of every triathlete I’ve discussed hydration with has to take in less water when running than riding on the road.

I come from a running background, which is why I’m asking.

I’m just curious what you think it is specifically about cycling that increases the need for hydration. Additional airflow over the skin leading to greater evaporation of sweat?

Not need… ability to process.

Your sweat rate is affected by a lot of factors that don’t influence gastric emptying, and gastric emptying is affected by factors that don’t change sweat rate.

Okay, well, same question.

What is it about cycling that leads to higher gastric emptying rates?