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Can A Triathlete Really Break 7 Hours Over The Iron Distance?

We dig into the science and numbers behind the audacious Sub7/Sub8 project.

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UPDATE: Kat Matthews, runner-up at the 2021 Ironman World Championship in St. George, was announced at Charles-Barclay’s replacement due to injury. Joe Skipper was announced as the replacement for Alistair Brownlee, who pulled out due to injury.

It’s one thing to say that records are meant to be broken. It’s another to actually get out of bed and do it.

But that’s the promise of the Sub7 and Sub8 projects—which will attempt to break the seemingly unbreakable seven-hour barrier (men) and eight-hour one (women) in an iron-distance triathlon. How fast will the athletes actually have to go, and what little tricks will they have up their sleeves to make it happen? We tap the experts to look into the science behind the hype at next-year’s event.

The Players

The men and women who will try to write history include the double Olympic champion Alistair Brownlee (GBR), the 2012 London Olympic champion Nicola Spirig (SUI), three-time Kona runner-up Lucy Charles-Barclay (GBR), and Kristian Blummenfelt (NOR)—current holder of the fastest half-iron distance time ever (3:25). And to smash the ambitious target, they will race head-to-head against one another, but they’ll also have the benefit of pacers and drafting throughout the event.

The project is supported by the Phoenix Foundation, a nonprofit organization that promotes “physical activity as a way to improve health and wellbeing among children with a particular focus on those in disadvantaged situations,” as the association’s website reads. They do so through events and initiatives like Sub8 and Sub7, but they also deliver local and regional programs to assist young people. The attempt also has the support of the Mana Group, a sports and entertainment group launched in 2018 by former pro Chris McCormack and Wojciech Kruczynski (founder of Phoenix).

The foundation will give financial support to the athletes to select their pacers. But their training and strategies will be individual and not provided like other exhibition-style record attempts, like Breaking2 and then Ineos 1:59 (which broke the 2-hour marathon barrier back in 2019).

Alistair Brownlee has gone back and forth between long-distance racing and the World Triathlon short-course circuit since winning his second Olympic gold medal in 2016. Photo: Nigel Roddis/Getty Images for Ironman

How The Challenge Was Born

“There were a few of us talking about challenges in triathlon, and we were talking about the iron-distance and how fast is it possible to do it,” said Brownlee. “But there was no point saying, OK, let’s do it in 7 hours and 20 minutes. So we said, OK, 7 hours it is then.”

The next step was to break it down into smaller pieces.

“The swim and run are quite limited in the gains you can get,” Brownlee said. With that in mind, the team started with a possible time for the swim and the run leg (45 minutes and 2 hours 30 respectively), and consequently calculated it’d require 3 hours 45 minutes for the bike and the transitions. At this point, more questions arose.

“OK, so what does it take to do the bike in actually 3:40 or faster? Obviously, a speed of more than 50km/hr is not possible on your own, so what kind of team time trial does it take, and what kind of power requirement is that? You can module it pretty accurately, which is what I did, and I worked out it was possible,” Brownlee said.

The Drafting Question

Everyone involved agrees the bike segment and the bike strategy will be the most critical part of the challenge. During the event, pacing and drafting will be allowed, and each athlete will be able to use up to 10 pacers. They will be able to use them “in any combination for any discipline, and they do not need to complete any set distance,” said a spokesperson from Mana Group. The pacemakers can also be used multiple times within a single discipline and for more than one discipline. There will be no restrictions on drafting, but the pacers cannot physically assist the athletes.

“Obviously, the bigger time [gain] is going to come on the bike, so it’s important to get the bike right, the course right, the team right,” Brownlee said.

Although they will nail the details at the end of the season, he says that they will adopt a team time trial strategy and try to hold an even but very hard pace for the whole segment. That’s also easier said than done, but science is on his side. Several studies have shown the advantages of drafting in both a peloton of more than 100 riders and in a TTT of up to nine cyclists.

This paper, published in 2018, showed that in the rear of a peloton of more than 100 cyclists, riders well-protected from the wind could benefit from a drag reduction of up to 90-95% compared to an isolated rider. And this paper has shown that riders cycling TTT pacelines can benefit up to a 50% in drag reduction compared to an isolated rider (with percentages changing depending on the number of riders in the formation and position of the individuals in that line).

The Numbers

What they plan to deliver at a still undisclosed location at some point in 2022 is brutal and straightforward: The men will try to complete the swim in less than 40 minutes, the bike in less than 3 hours 45 minutes, and the marathon in less than 2 hours 30 minutes. That’s a big difference from the current record, held by triathlon royalty Jan Frodeno, who clocked a 7:35:39 in Roth, Germany, in 2017 (Brownlee’s fastest Ironman time is 7:45:20, which he ran in Australia in 2018; his splits were 46 minutes, 4:10, and 2:43 for each leg, respectively).

It’s only when you break the overall time into smaller chunks, that the challenge becomes even more ridiculous. To actually swim the segment in 40 minutes means that Brownlee and Blummenfelt need to swim at a pace of 1:03 per 100m (or :57 per 100yds), a good 9 seconds per 100m faster than Frodeno in Roth—and a total of five minutes faster than his swim time in that occasion (45:22). However, if we look at stats from the website, it seems somewhat doable and in line with Barrett Brandon’s 38:06 at IM Chattanooga in 2014—though on a current-assisted swim course.

Cycling 112 miles in 3 hours 45 minutes would equal an average speed of 30 mph, while Frodeno’s speed in Roth was 26.98 mph. That would be riding faster than in a typical cycling World Tour stage, though the fastest Tour de France stage was recorded in 1999: 198 km at 50.4 km/h (31.3 mph). However, it would be similar to the Tour’s fastest team time trial (TTT), which was recorded in 2013 by Orica GreenEDGE; they completed the 40K (25 miles) in 35.85 mph. In a more apples-to-apples comparison, the fastest bike split ever recorded in an IM event is Andrew Starykowicz’s split at Ironman Texas in 2017: 4 hours and 1 minute at 27.8 mph.

And finally, to run the marathon in 2 hours 30 you’d have to hit a run pace of 5:43 min/mile—versus Frodo’s 5:58/mile world record-setting pace. Anyone even getting close to that 2:30 barrier will end up smashing the current run-leg record of 2:36.

On the other hand, the women target a swim faster than 45 minutes, a bike leg under 4 hours 15 minutes, and a marathon split quicker than 2 hours 55 minutes. The standing women’s record was also set in Roth, in 2011, by Brit Chrissie Wellington. Charles-Barclay’s fastest iron-distance was also recorded in Roth in 2019 (8:31:09 with a 49 swim, 4:39 bike, and 2:59 run).

In average pace numbers, that would equate to a pace of 1:11 per 100m (1:04 per 100y), cycling at 26.3 mph, and running at 6:40 min per mile. Charles-Barclay recently swam the Team GB Olympic trials for the 1,500 in 16:46 and at a pace of 1:07 per 100m (1:01yds.). According to, the fastest swim time recorded in an IM event on a current-assisted course is the blistering 39:56 by Anna Cleaver (Chattanooga in 2014)—and that was a 1:03 per 100m (:57 per 100yds.).

The fastest bike split for the women is still Daniela Ryf’s 4:26:07 in Kona in 2018 (25.2 mph), while the fastest marathon in an IM is Kristin Moeller’s 2:41:57 from Ironman UK in 2011 (6:10 min/mile).

The scale of the efforts required seems out of this world. So what do they need to do to step up their game that much?

The Science

“They need to know their own physiological profile in the three disciplines, as well as the pacers they will use, and have an effective drafting strategy. I believe they can make it, but there is absolutely no way they are going to do it without effective pacing and drafting strategies,” said Nicholas Willsmer, high-performance triathlon coach and lecturer at the University of Bath, England.

From a simple physiological point of view, explains Willsmer, they will need to understand where their current thresholds are now in relation to their past best performances. Then they need to see if they have the shape to repeat them—and then calculate how much they need to shave off to hit the new target.

Willsmer believes that the key will be the bike (more on this below), but even drafting strategies in the swim and run segments will be crucial. A study conducted in 2003 has shown that a drafting swimmer can benefit up to 21% in drag reduction if they are swimming right behind the lead swimmer. In lateral drafting, the benefits are less pronounced at 6% if the second swimmer is placed 20 inches from the hands of the lead swimmer.

“From race analysis of Alistair Brownlee, using his Ironman Australia times, he currently has a swim speed of ~1.36 meters per second [1:13 per 100m] with a wetsuit and is targeting ~1.58 meters per second [1:03/100m], and that’s approximately 14% faster. It is questionable if this is achievable due to his swim times already being conducted in a wetsuit,” he said. However, “Lucy Charles Barkley currently has a swim speed of ~1.31 meters per second [1:16/100m] targeting 1.41 meters per second [1:10/100m], and that’s approximately 7.5% faster. But her current swim time is non-wetsuit from Kona, and therefore with drafting and a wetsuit, this is possibly achievable.”

In the run, drafting and technology advantages would be less substantial than in the swim, but could still count for ~2.7% thanks to the newest springy shoes on the market, and around 6.5% decrease in oxygen uptake according to another study if runners draft pacers one meter behind them.

Willsmer also calculated their current and target run times, and even in that case, the improvements are potentially realistic if the athletes are able to conserve energy expenditure in the swim and bike and hydrate and fuel effectively. “Alistair Brownlee currently has a run speed of approximately 4.3 meters per second [6:07 min/mi] and is targeting approximately 4.6 meters per second [5:48/mi.] which is approximately an 8% improvement. While Lucy Charles-Barkley currently has a running speed of 3.8 meters per second [6:55/mi.] and has a target of 4 meters per second [6:43/mi.] which is approximately a 6% improvement,” he said.

Willsmer doesn’t believe their training needs to shift that much unless they’re coming from a purely Olympic distance-focused program. What they will need to be accustomed to is the bigger picture and all its micro-components: race course, environmental conditions (air temperature and humidity), nutrition, gear, and technology selection, and their own psychological approach.

Nicola Spirig won an Olympic gold medal in 2012. Photo: Charlie Crowhurst/Getty Images for Ironman

The Bigger Picture

Someone who knows a thing or two about breaking down these challenges is Professor Andy Jones from the University of Exeter, England, who had served as Chief External Scientific consultant to Breaking2 and later advised Ineos 1:59.

“The team needs to be completely focused on the goal and work towards the limitations that can make the performance breakthrough. I think it is probably difficult to improve their physiology. It’s really trying to think out of the box and find other areas where there might be some benefit,” he said. “In Breaking2, everything was organized by the team, from expert advice to logistics. The athletes only needed to train and race hard. It would be hard if the athletes needed to coordinate everything on their own.”

He also believes that Sub7 and Sub8 will be even “trickier because of the three disciplines, the transitions, and simply because of the total duration. There is much more time for things to go wrong. Even more so than the marathon, getting the nutrition strategy and the drafting will be crucial.”

Only time will tell if this feat can actually live up to the hype, and particularly when the figures are broken down to their respective parts, it seems like a nearly impossible feat. Between the talented athletes, the team behind them, and the pacers literally surrounding them on the day of the event, they’ve at least got a chance. Regardless of whether they succeed or not, the attempt will be worth the spectacle.

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