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

July 18th, 2010

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.

  1. July 21st, 2010 at 17:26 | #1

    If a recreational 5k time is 19:51, I’m not sure what that makes me. 😉

    Interesting info, but I have a feeling, as you elude to, that results would diminish as distance is increased.

  2. alex
    July 21st, 2010 at 23:23 | #2

    Yes, I definitely should have put “recreational” in quotes (it was the word the researchers in the article used to describe their subjects) — they were clearly pretty accomplished triathletes!

    And I agree that the “no holds barred” approach gets riskier the longer the distance. I’d hate to see an Ironman competitor leave nothing in the tank for the run…

  3. alex
    July 22nd, 2010 at 21:24 | #3

    From jgill [I accidentally deleted the comment — sorry!]:

    “Have a sprint triathlon soon and I am going to give this a try. Don’t worry, if I come in last place, I will not hold anyone accountable :-). I have often wondered about this approach and it is good to have data to suggest this might be the way to go for sprint triathlons.

    Also, love the site and keep the data coming!”

    Good luck, and let us know how it goes!

  4. July 29th, 2010 at 18:42 | #4

    I agree with Tammy, having coached triathletes of a wide range of abilities and over different distances. This study is fairly short on data (few subjects) and only tested short course racing efforts. Most sprint distance triathlons have at least a 30km bike leg, and I believe that additional 10 km would change the outcome to a significant degree. I also have a great deal of Lactate Threshold data that I have used to properly pace athletes to personal best at all distances. I feel very comfortable saying this is not a good strategy and becomes exponentially bad the longer the race.

    Keep the information coming, and I think your site is a great resource and appreciate what you do.

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