How Much Fluid do You Need on the Bike?

Speedfil1This is one of the more common questions of people racing triathlons, beginners and experienced triathletes alike, how much should you drink during the bike ride? And to be clear and keep it simple, I’m keeping the conversation to “fluid”, which includes water or water plus electrolytes. Adding calories to the picture complicates things, which I’ll cover in another blog, so for now, we’re talking water, with or without added electrolytes (i.e. Nuun tablets), only, no calories.


The simple answer is this, 20 to 30 oz. of fluid an hour, is enough fluid to keep you hydrated during the ride and for the start of the run. That’s quite a lot variance, 1-1.5 small water bottles (and for reference, I say that small/standard sized water bottles hold 20 ounces, larger bottles hold 24), the reason being we all sweat at different rates, we all react to the stress of racing differently, and we all react differently to changes in heat and humidity. There really is no magic formula for this, so you should start out with one bottle an hour and see how your races/training days go, and adjust up accordingly until you find the right amount.


So I said that was the simple answer, and if you’re the “average” person, with an “average” sweat rate, who reacts “normally” to hotter and more humid conditions than what you normally train in, this might be as far as you need to read. But that last sentence adds a lot of conditions, doesn’t it? How do you know if you’re an average sweater? Or that your body deals with stress under racing conditions like the average person or with changes to the weather? That’s the thing, and this is why when people move up to longer distance races, say half and full Ironman distance, they run into trouble, because they don’t know the answers to these question, or even know that they need to figure them out. Let’s look at this one step at a time to see what you need to be thinking about.


For most race distances under the half Ironman or equivalent, the simple answer works for most people, when their races are in the 2-4 hour range. Given that you drank enough, added calories as you saw fit (based on your training and racing experience), not drinking enough fluid shouldn’t lead to you being unable to finish the race, although it might cause you to under-perform. We have a 2-2.5 hour window of racing where calories aren’t really needed to finish a race, but water and possibly electrolytes are definitely needed. Beyond that adding calories is absolutely necessary and like I said, I’ll delve into that on another day.


When considering how much fluid you need on the bike, you need to look at how much fluid you will be drinking the whole day, starting from when you wake up, when your wave goes off, and when you expect to finish. If you wake up long before your race starts, then you need to be sipping water all morning to stay topped off, realizing that we all wake up a bit dehydrated from sleeping. By the time you hit the bike it’s been a while since you drank anything (and hopefully not too much lake/stream/ocean water since then!), you’re already a bit behind compared to how you started out. I recommend that you take a sip of water either in T1 or early on the bike, but that you don’t really start drinking too much until you’ve settled in on the bike, maybe even 10-15 minutes down the road.


Most people subscribe to the theory where you keep sipping water the whole time you’re riding, staying topped off, while a few claim that only drinking a lot every 15 minutes or so allows the body to think it’s dehydrated which leads to better absorption in the stomach. I personally prefer the former versus the latter, but if that’s not working for you, try delaying when you drink and drink more to see if that works. I recommend people that do longer races have an aero drink system attached to the aerobars so that when you’re down in the aerobars fluid is readily available at all times, without having to reach down or back for a bottle, facilitating drinking more and without getting out of the aero position and creating more drag.


The caveats that need to be added are in response to my original claims about “average” people and how they adapt to changes in the climate. You know if you’re a heavier than normal sweater if your clothing and helmet are soaked with sweat regardless of the temperature out or the humidity. Even better, if you ever train indoors on the bike, say on your own trainer or in a spin class, and you leave a small lake of sweat around you or a stream of it heading off in one direction or another, tend towards the 30 oz. of fluid an hour versus 20, at least to start.


As for you how you adapt to racing say in Hawaii in June compared to training where it’s 60-70 degrees with no humidity, given time to acclimate our bodies figure it out, but it typically requires you drink more fluid to compensate for the increased sweat rate. Some people go with the zero acclimation plan, meaning they fly in as late as possible and race without any kind of acclimation, hoping they get through the change with little or no affect. I’m not a fan of that theory, preferring to give myself the better part of a week to get right before I race.


Something to realize if you’re thinking that you really don’t need to change your training habits with regards to training your body to take in more fluids, and that on race day if you feel thirsty you’ll just drink more, that doesn’t always work. We call eating and drinking the fourth leg of a triathlon, particularly important for longer races, so we actually have to train our stomach to deal with the increase in fluid and calories over the normal amount we take on for a simple training ride.


You can’t train to 20 oz. of water an hour and say 100 calories an hour and then on a hot race day suddenly take in twice as much and expect our bodies to just go along with it. Sweating and trying to shed excess heat while racing requires blood to be shunted from our stomach and muscles to our extremities to try and cool off. This results in less blood flow to the stomach which causes our ability to absorb fluid and calories to drop off (while we’re pumping in more fluid), and less blood flow to our muscles, causing us to have to slow down to avoid the possibility of cramping due to overexertion and dehydration and the aforementioned GI issues.


You have to practice eating and drinking how you expect to do it on race day in your training, else bad things can definitely happen. As president of our local tri club I had a friend of mine, Terry Thomas, a nutritionist at UCSB and an elite age group triathlete, talk at one of our meetings on the subject of proper eating to fuel our bodies on race day. She started out her talk by saying this, the best thing that we can do to make sure we take on enough calories is to hydrate, hydrate, hydrate. So when a nutritionist and experienced racer (whose husband BTW, Duncan Thomas, competed at Ironman Hawaii nine times and used to hold multiple age group records there!), says we need to focus on drinking, I take notice.


If you’re now wondering how do I really know if you’ve drank enough fluid during the ride, there’s really only one way, at some point you have to pee, and it better be sooner than later. Most people finish sprints and Olympic distance races without having to stop at a porta potty, but hopefully not shortly thereafter you should have to go. If you don’t go until say hours later, then you were dehydrated and your performance likely suffered. Many athletes pee during the bike rides during half and full Ironman distance races (sometimes while riding, sometimes they stop…), or maybe they hold it until T2 during a half, and then as needed on the longer runs.


But think about it, how many days go by where you are drinking a lot of fluids over a 5-7 or 9-17 hour day and don’t have to pee? If they were the case on a “regular” day, you would know you’re dehydrated, so realize the same thing holds true on race days, where it’s way more important to be hydrated to keep cool, to help digest calories, and to keep our muscles from cramping. I personally believe that dehydration from not drinking enough plain water is why most people cramp, as well as poor training and poor pacing, but more on that another day, a whole nother can of worms!


So the bottom line to all of this is to practice drinking on your training days to match what you expect to do on race day, to drink a little bit the whole time before you start the run, even to start out a bit “sloshy” as local tri coach Mike Swan always liked to say, so that your body and muscles are ready to go on the run, and to stay topped off as best you can on the run. Remember this, if you’re starting to feel like you should be drinking then you’re probably already a little dehydrated, so stay in front of it, don’t lose focus on your drinking (and eating, and pacing…), and this should help you to race at your expected pace for the whole race, matching your training pace, and finishing feeling strong still.


Good luck and remember, hydrate, hydrate, hydrate!

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