Tag: triathlon

Posted on

Higher carb intake = faster Ironman finish

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

***

Here’s a graph, from a recent paper on nutrition during long (marathon and longer) endurance competitions, that’s worth a close look:

What do you see? A bunch of dots scattered randomly? Look a bit more closely. The data shows total carb intake (in grams per hour) by racers in Ironman Hawaii (top) and Ironman Germany (bottom), plotted against finishing time. It comes from a Medicine & Science in Sports & Exercise paper by Asker Jeukendrup’s group (with several collaborators, including Canadian Sport Centre physiologist Trent Stellingwerff) that looked at “in the field” nutritional intake and gastrointestinal problems in marathons, Ironman and half-Ironman triathlons, and long cycling races. The basic conclusion:

High CHO [carbohydrate] intake during exercise was related to increased scores for nausea and flatulence, but also to better performance during IM races.

So basically, taking lots of carbs may upset your stomach, but helps you perform better. It’s important to remember that gastrointestinal tolerance is trainable, so it’s worth putting up with some discomfort to gradually raise the threshold of what you’re able to tolerate.

Anyway, back to that graph: while it may look pretty random, statistical analysis shows a crystal-clear link between higher carb intake rates and faster race times, albeit with significant individual variation. Obviously there are some important caveats — it may be, for example, that faster athletes tend to be more knowledgeable about the benefits of carbs, and thus take more. Still, it’s real world data that tells us the people at the front of the race tend to have a higher carb intake rate.

One other point worth noting. The traditional thinking was that humans generally couldn’t process more than 60 grams of carb per hour. Over the last few years, thanks to multiple-carb blends, that threshold has been pushed up to 90 grams of carb per hour. In this data set, about 50% of the triathletes were taking 90 g/hr or more.

[UPDATE 10/26: Given all the comments below about the variability in the data, I think it’s worth emphasizing what should be a fairly obvious point. The only way this data would come out as a nice straight line is if Ironman finishing time depended ONLY on carb intake, and was totally independent of training, experience, talent, gender, body size, and innumerable other factors. This is obviously not the case, so we should expect the data to be very broadly scattered. What the statistical analysis shows is that, with p<0.001, faster finishers tended to have consumed carbs at a higher rate. There are many ways to interpret this data; one possibility is that, if your carb consumption is below average, you might wish to try a higher rate of consumption (e.g. 90 g/hr) to see if it helps.]

Posted on

How many carbs can a super-carb-absorber absorb during a triathlon?

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

***

Following up on my post on maximizing carbohydrate absorption during exercise a few months ago, I got an interesting e-mail from a triathlete named Josh (yeah, I’m still way behind in catching up on e-mail since the trip to Nepal!). His question was basically: Forget about averages, how high can an individual outlier push his or her rate of carb absorption, with training and good genetics?

I’m a tall and lean guy and at Ironman this past year I ate 600 calories [150 g] per hour for 5 hours on the bike and ate at around 450 cal [~112 g]/hour on the run. That’s well in excess of ANY average rate that anyone has ever suggested is “possible on average”…

It’s an interesting question. After all, as Josh pointed out, the average marathon time is around four hours, but we don’t focus our training discussions on how to be average. So I dug up Asker Jeukendrup’s recent review of multiple transportable carbs to see if it would shed any light.

The first key point, of course, is the difference between ingestion and absorption. While Josh was ingesting 150 g an hour, that doesn’t mean all those carbs were reaching his muscles — they could be hanging around in his stomach, or passing through his intestine without being absorbed into the bloodstream, destined for an eventual rear exit. A very nice table in Jeukendrup’s paper sums of the results of 13 studies: Continue reading “How many carbs can a super-carb-absorber absorb during a triathlon?”

Posted on

Elite triathletes change muscle recruitment off the bike

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

***

Following up on last week’s post about the increasing use of 3-D motion analysis, there’s a new Australian study examining the running stride of triathletes coming off the bike in this month’s Journal of Sports Sciences. They took  “moderately trained” (i.e. club level) triathletes and measured their stride during a 30-minute, either with or without a bike ride beforehand, using EMG to measure muscle activation and motion capture to measure the stride.

The basic finding: 14 out 15 triathletes showed no difference in muscle recruitment between the two runs, but five of them did show kinematic differences (their joints were at different angles and moving differently). What’s surprising is that this is basically the opposite of what they found in a similar study of elite triathletes, who kept their stride pretty much constant but had different muscle recruitment patterns off the bike.

What this suggests is that it’s difficult to run “normally” coming off the bike, but elite triathletes have trained long enough to learn how to send different signals from their brain to their muscles in order to reproduce their normal stride.

Therefore [the authors conclude], training interventions focused on quickly restoring optimal running movement patterns after cycling may be advantageous for moderately trained triathletes’ performance.

The only problem: I’m not really sure what those interventions would be, other than doing your training in a 3-D motion capture system!

[Thanks to Steve Magness for the tip-off.]

Posted on

Doping in triathlon: the passport system

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

***

Had an interesting chat yesterday with Leslie Buchanan, the International Triathlon Union’s Vancouver-based director of anti-doping. She’s here with WADA’s outreach program, setting up daily in the Athlete’s Village to answer questions about the rules and the reasons for them. (Most of the questions she’s fielding are about the whereabouts program, which requires athletes to be reachable by their country’s anti-doping officials at all times.)

Anyway, I asked her why triathlon seems to have dodged the perception of widespread dirtiness that plagues its constituent sports (perhaps cycling most of all, but distance running and swimming have hardly been squeaky clean). She noted that triathlon has really only had four high-profile busts: Dmitriy Gaag, Brigitte McMahon, Mariana Ohata and Wang Hongni. Part of it is money: as a newer sport that’s only been in the Olympics for a decade, there wasn’t the same incentive for triathletes to dope until relatively recently.

Obviously that’s no longer the case. But I didn’t realize that triathlon has followed cycling’s lead and, starting this year, instituted a “biological passport” program. While cycling is apparently aiming for 12 blood tests per year, triathlon is starting with a more modest program: a minimum of three and aiming for six bloods per year for each of its top 50 men and women. That will hopefully establish a baseline so that deviations will trigger an alarm even in the absence of a positive urine test. The system went into effect at the beginning of 2010.

I’d heard a lot of talk about biological passports, but I hadn’t realized that they’re actually being implemented in some sports. Anyone know which (if any) other sports have them? Does track and field?

Posted on

Bike-run time is fastest when you go all-out on the bike

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

***

For the triathletes out there, an interesting study has been posted online for publication in a future issue of the European Journal of Applied Physiology: “Combine cycle and run performance is maximized when the cycle is completed at the highest sustainable intensity.”

A pair of Australian researchers asked a group of triathletes to perform a series of four 20K bike/5K run time trials, with the intensity of the bike ride varying from 80% to 100% of max intensity (compared to an isolated bike trial they’d done previously). As expected, going harder on the bike led to slower times for the run — but the effect was most pronounced for just the first kilometre of the run, after which it didn’t really matter how hard the subjects had gone on the bike. As a result, the fastest overall bike-run times came when the effort on the bike was highest. In other words, holding back in any way on the bike loses you time that you can’t make up on the run.

Now, there are a number of caveats. The study was small (5 men, 3 women), but the effect was very clear-cut (average times of 62:40, 59:53, 58:29 and 56:37 for the four trials, going from easiest to hardest for the bike leg), so that’s not likely to be an issue. The fact that the distances were 20K-5K instead of 40K-10K is unfortunate. The authors do a song and dance about how the sprint distance is “growing in popularity” so that’s why they decided to study it, which seems absurd. I assume the real reason is that it would have been much harder to get volunteers to do that many 40K-10K efforts in succession. Also, it was a lab study done on stationary bikes with no wind resistance, and the triathletes were recreational — their average 5K time (not preceded by a bike ride) was 19:51.

Still, bearing all these things in mind, it’s a data point:

It is unclear if this relationship would hold for longer-style triathlon race formats, full triathlon races which also include a prior swim leg, races that involve a draft-legal cycle leg or with highly trained or elite triathletes. However, our results suggest that time lost on the cycle leg is unlikely to be made up on the run leg.