Science Says an Ironman Under Seven Hours Is (Somehow) Possible


On June 5, four of the world’s greatest long-distance triathletes will be aiming for some of those round barriers that we’re excited about. There’s the four-minute mile, the two-hour marathon… and now, the seven-hour (for men) and eight-hour (for women) Ironman triathlons.

The catchy-named Pho3nix Sub7 and Sub8 Powered by Zwift races are explicitly modeled after Eliud Kipchoge’s two-hour marathons. Like the Kipchoge races, they are funded by an enthusiastic billionaire (in this case Polish businessman Sebastian Kulczyk, through his foundation promoting children’s fitness). They will be run on a specially designed course with modified racing rules allowing for a bunch of pacemakers. And like the original Breaking2 race, the initial reaction from knowledgeable observers was that the goal is probably out of reach.

In anticipation of the attempt, professional triathlete Antoine Jolicoeur Desroches, a doctoral student in sports science at the Université de Sherbrooke, along with his supervisor Éric Goulet, published a preprint (i.e. an article submitted to an academic review but not yet peer-reviewed) to assess whether an Ironman below 7 is possible, and if not, how much external help (like pacing) would be needed to bridge the gap. He started out as a skeptic, but as the final details of the attempt came to light, he came to believe it might be possible. Here’s why:

The backstory

Chances are you haven’t spent many nights lying awake and wondering if humans would ever break the seven-hour Ironman barrier. In triathlons, the focus has always been more on head-to-head competition than time. I suspect that’s largely because it’s so hard to compare times on different bike courses. In Olympic triathlons, drafting is allowed, which means times are even more context specific. Drawing on the bike is not allowed in Ironmans, but it is difficult to compare topography and prevailing weather conditions on courses around the world.

However, the records are kept. Over the Ironman distance of 2.4 miles of swimming, 112 miles of cycling and 26.2 miles of running, the record set in the inaugural race in 1978 was 11:46:58, and the first women’s record was 12 h 55 min 38 s was established. one year later. The records have steadily dropped to 7:27:53, set by Jan Frodeno in 2021, and 8:18:13, set by Chrissie Wellington in 2011. Defending Olympic champion Kristian Blummenfelt also clocked a 7:21:12 l last year, but the swim was current-assisted and therefore not recognized as a record. Here’s a graph of the progress of the men’s record, taken from Desroches’ article (which unfortunately only focuses on the men’s side):

(Photo: Desroches et al, SportRXiv)

If you extend that straight line, you see that the current trend predicts an Ironman below 7 in 2049. That’s a long time away.

To assess the feasibility of the challenge, you can also add up the fastest individual stages ever recorded in official competition: Jan Sibbersen’s 42:17 swim, Jan Frodeno’s 3:55:22 bike and the 2:00 marathon. 34:50 by Gustav Iden. The total of 7:12:29 gives you an idea of ​​the magnitude of the sub-7 challenge. Another clue: the half-Ironman record, held by Blummenfelt, currently stands at 3:29:04: almost exactly the pace required for an under-7. Given the typical 7.3% slowdown seen in elite long distance triathletes, you would expect this to translate to a time of 7:24:58, which is very close to the current assisted time of Blummenfelt.

The bottom line: This won’t happen in an ordinary race. And indeed, the Ironman World Championships, delayed from last year, took place earlier this month. The winners were Blummenfelt in 7:49:16, while Swiss star Daniela Ryf won the women’s race in 8:34:59.

What it would take

Desroches and Goulet break down barriers and opportunities for improvement in each of the three disciplines. There are unique individual considerations: wetsuits in swimming, bike technology in cycling, shoes in running. And then there is writing, which is relevant in all three disciplines. It quickly becomes clear that obstacles are only plausible if (unlike the official Ironman competition) drafting is allowed, which will be the case in the Pho3nix race.

It is well known that drawing is much more important in cycling than running because the speeds are much higher. Swimming is still slower than running, but drawing can still make a substantial difference because water creates more drag than air. The researchers cite previous estimates that drawing can reduce energy expenditure by 5-10% or increase speed (at a given level of energy expenditure) by 3.2-6.9%. I would take those numbers with a big grain of salt, as they came from very short 400 meter swim trials. Still, if you take the more optimistic estimate, you’re looking at a potential saving of about three minutes over 2.4 miles.

Thanks to all the discussion around the Breaking2 marathon project, a lot of attention has been devoted to saving drafting time in a marathon. At the two-hour pace, estimates ranged from about one to six minutes. At the slower pace of the final leg of a triathlon, writing will be less beneficial. Desroches’ guess is that the savings will likely be between one and two minutes.

Shaving 28 minutes off Frodeno’s record, two minutes swimming and three minutes running leaves plenty of work to do on the bike. Fortunately, this is by far the longest stage, usually contributing more than half of the total time, and it’s also the stage where the repechage will help the most. In Team Pursuit formation, the third and fourth runners in the line reduce their drag by 55 and 57 percent respectively. This is a big problem, as cyclists spend up to 90% of their energy overcoming air resistance at high speeds.

If you run a few numbers, things get interesting. With generic parameters for weight, frontal area, drag coefficient, etc., you can estimate that a hypothetical cyclist would need to produce 300 watts to complete a 180 km bike stage in about four hours. If, as Desroches estimates, it could reduce its power output by up to 40% while firing, that suggests it could be riding at the equivalent of 500 watts (while actually only putting out 300 watts) and finish the step in 3:19, saving about 40 minutes. We speak now.

In a way, it’s reminiscent of Project Breaking2, where calculations that included drafting, the effects of the new Vaporfly shoes, and various other potential time savings suggested that Kipchoge should be able to run a ridiculous time like 1:54. The reality, however, does not always conform to our pie-in-the-sky calculations. Even the best riders won’t be able to sustain anything close to a perfect team pursuit formation for 112 miles, so the actual savings will be significantly less than 40 minutes.

Desroches and Goulet also spend time analyzing other factors like course design, and they offer some great suggestions: find a place with calm salt water, low temperature and low humidity, like Bahrain, for example . Start the race late enough in the day for the sun to set at the start of the marathon, as the optimum temperature is warmer for cycling than for running. Optimize elevation and slope and turns and so on. But the bottom line, at least from my perspective, is that we’re only having this conversation because there are huge potential savings to be had on the bike.

The plan

That’s the theory. In practice, the race will take place on June 5 or 6 (depending on the weather) at the Dekra Lausitzring, a race track in Germany. The elevation is only 380 feet and the forecast temperature will be between 53 and 73 degrees Fahrenheit. The course will begin with a one-way swim in the calm waters of Lake Senftenberg, followed by a ten-mile ride (88-foot drop) to the race course, where they will cycle 3.6 miles in loops and 2.2- mile loops for running.

The two male contenders are Blummenfelt and Alistair Brownlee, the British double Olympic champion. The contenders are two-time Swiss Olympic medalist Nicola Spirig and Britain’s Katrina Matthews, silver medalist at the Worlds earlier this month.

Interestingly, unlike the centralized approach of the Breaking2 race, each of the four competitors assembles their own support team and makes their own tactical decisions. The key constraint: they are each allowed to take ten pacemakers, which they can deploy as they see fit in the three events. During running and cycling, pacemakers can substitute indoors and outdoors; during the swim (from my reading of the rules) all pacemakers must start with the competitors, and once they drop out they cannot rejoin the race.

Another detail I noticed: Competitors are allowed to wear any wetsuit, with no thickness limit, unlike the five millimeter limit in official Ironman races. Desroches notes research that found a 6% increase in swimming speed with a wetsuit due to its buoyancy, but he doesn’t think the extra thickness will bring much more benefit. There may be other nuances in the rules that I missed, leaving the door open for surprises to be revealed on race day.

In summary: it’s not out of the realm of possibility for the men, and the same arguments apply to the women’s race, where the current gap is a more modest 18 minutes. In a sense, after looking at Desroches and Goulet’s analysis, success in either run would be less surprising than either of Kipchoge’s runs. Few people thought that drafting was important in marathons or that elastic shoes could make a big difference. on the other hand, everyone already knows that drafting is a big problem in cycling. Still, there’s a huge gap between acknowledging that the repechage is important and believing that any of these four athletes will make it through the seven or eight hour mark – enough of a gap, perhaps, to entice you to tune in to the live stream. free live 9.5 hours. .

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