Packing Your Calories for a Half Ironman Bike Ride, Part I

I’ve wanted to write about how many calories you should consume during longer distance races, longer than Olympic distance, but have recently been reminded that how I describe getting this all on the bike is complicated. At a SB Tri Club meeting the other night the guest speaker talked about the details of racing, and how to get people to understand it’s the subtle things we do while we’re racing that lead to our ultimate success, while ignoring them lead us to not meet our goals. Hearing that, I realized that I needed to present my ideas on this in a different way, else people wouldn’t use the information. calories on the bike

The ultimate goal is to take on enough water and calories to prepare you for the 13.1 mile run that follows the bike. What I propose to people always sounds like way too much water and calories, while I know that after talking to so many athletes after completing their half Ironman races that they had very poor results on the run. Typically their pace falls off dramatically after 10k into the run, cramping happens a lot, GI problems pop up, and they struggle to meet their goal times. When asked about the how much water they drank on the bike and how many calories they consumed, they all seem on the low side, just enough for a typical bike ride, but not enough to get them through another 1.5-2.5 hours of running.

Eating on the bike sets up the run; you aren’t just fueling yourself to ride 56 miles. That’s why we call it the fourth leg of triathlon, not something to be ignored, but an essential part of a successful event.

There are formulas out there that describe how many carbohydrate calories you should consume per hour, based on body weight alone. There are also formulas that include how fast you ride. I find speed too vague to use as it doesn’t take into consideration a person’s level of fitness. A formula based on say what percentage of your threshold HR you ride at or what percentage of your FTP (for power based riders) you ride at, would be more exact, but this is where it gets complicated and people drift off to do their own thing.

But let’s say you did all this, you know your FTP, what percentage of your FTP you ride at during a half IM bike split, your weight, etc., and you calculate that you should consume 272.5 calories an hour. So is that the final answer? No, as this is just a starting point, and now you have to go out and train under race conditions to see if your body can consume that many calories and allow you to maintain your pace and level of effort. Or maybe you find out that you didn’t take on enough calories and have to slow down, so you gradually bump up the number until you find the tipping point between too many calories that causes GI issues and too few calories that cause you to slow down.

Remember that as triathletes, experimenting as we move up in distance with pacing, drinking, and eating, we are a science experiment of size 1, so we need to take our time. Only change one aspect of your training on each ride/run so as not to confuse the outcome, good or bad. For example, if you find yourself having to slow down after consuming 250 cal/hr. on the bike, on your next ride, on the same course, bump up the calories to say 300 cal/hr., while riding at the same pace. Don’t also slow down the pace to see if that works; only change one thing at a time.

Have I mentioned the correct mix of carbs and proteins and electrolytes? No, as once again, this is a topic for another day, to try and keep this simple. In a previous article I wrote, How Much Fluid Do You Need to Drink?, I tried to keep it simple, and did offer up the basic fact that I think you should take on 20-30 oz. of water per hour on the bike. Now that we’re adding in calories, in some TBD form, you need to increase your fluid intake level to accommodate the added calories. If you don’t take in extra fluids to help digest the calories, they’ll just wind up sitting in your stomach, you’ll get dehydrated, and well, as you can imagine, your race goes downhill from there.

I also won’t delve into the different kinds of calories to take on, solids, versus gels, versus liquids, and the makeup of each of these different types, with and without added electrolytes. Again, another layer of complication that I’m trying to avoid…

If you’re reading this and hoping that there’s a simple answer to this problem, here it is. 200-300 calories an hour is the answer and this will work for most of us, under most conditions. But, there are a few assumptions that go along with this simple approach. I assume that:

  • you’re doing a 12-16 week training program to get ready for the race and have time to practice eating and drinking under race day conditions
  • as soon as you have worked yourself up to the 2-2.5 hour long bike ride, you’re practicing consuming the same number of calories that you’ll be taking on race day, with the appropriate amount of fluid
  • you understand that you can only absorb 25-50% of the amount of calories burned while you ride, and that you use this number as a maximum number of calories to consume if you have figured out how many calories you expect to burn (which is based on body weight, speed, level of effort, etc.)
  • for a half IM race, 300 calories/hr. is a good maximum number, unless you ride at a very low intensity and expect to be on the course for a long time. If that’s the case you can take on more calories, plus water, to fuel the day and be ready for the run

To make this easy to understand (I’m still hoping to do that!), I’ll profile two athletes preparing for a half Ironman.

Craig Carlos
Expected ride time (hrs.) 2.5 3.1
Calories/hr. 250 300
Calories consumed on ride 625 930
Types of calories liquid solid & liquid
Ounces of fluid/hr. 30 30-35
Fluid consumed on ride (oz.) 75 93-108.5
Number of 20 oz. water bottles 3.75 4.65-5.425
Number of bottles on bike 3 2

The items of note are the expected ride time, how many bottles of water/calories they’ll each need to complete the race, and how many bottles they will carry on the bike. Craig will use a front loading aero water bottle system as his primary source of fluid/calories, while Carlos will have two bottles behind his seat (as will Craig), but he does have a water bottle cage on his frame to pick up a third bottle at aid stations.

The easiest way to do a race is to use the calories provided on the course, assuming that you spent time training with the specific mixture and that it works for you. Given that, then the race and logistics are simple. From the race website you can find out how many aid stations are on the course, then calculate how many calories in each bottle they’ll provide (this is kind of a big unknown actually, as it can vary), pack the bottles you plan on starting out with enough calories to meet your requirements, and you’re good to go.

You see that Carlos will include some solid calories (all or part of an energy bar), which means he needs to have some plain water onboard to help digest it. Be careful mixing too many different kinds of calories, like a carbohydrate drink mix and an energy bar, or a gel, as not all carb calories are created equal, so they might not get along in your stomach. I suggest using a Bento Box (no, not a Japanese lunch box, one made for a bicycle), that attaches to your top tube, with the energy bar cut into smaller pieces, as a way to carry solid calories. In case you decide you like using gels as a source of energy, you can use a gel flask that attaches with its own holder to the bike, or place it in a Bento Box.

You see how things get complicated fast,right? Next time I’ll go into more detail for each athlete, but maybe between now and then you can think about how you would pack this amount of calories on your bike, and get that much hydration. Till then, happy training.

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