In 2018, with ideal conditions, Cameron Wurf set the Kona bike course record in 4 hours, 9 minutes, and 6 seconds, at an average speed of nearly 27mph. His style of racing also changed the dynamics in the men’s bunch and forced other triathletes to take more risks. Possibly as a result of that, the overall course record on the Big Island has also been broken twice in the last two years: in 2018 by Patrick Lange (7:52:38), and again in 2019 by Jan Frodeno (7:51:13).

In the women’s field, this time without Wurf’s pressure, athletes like Daniela Ryf and Lucy Charles-Barclay have had the same effect on the overall and single-discipline performances. And they also did it in 2018, a special edition of the World Championships: Ryf set the bike and overall record (4:26:07 and 8:26:18 respectively), while Charles-Barclay finished in second place and with a swim course record (48:14.)

“The next frontier will be people learning to run fast. The bike is pretty much maxed out, as is the swim,” Wurf said. In other words, the bike and swim records are already world-class individually, but the run isn’t quite as much. And he has an interesting training episode to support his theory: “I’ve done 2-hour TT efforts with Froomey [Chris Froome] and G [Geraint Thomas]. They could maybe go one minute quicker [than me] going all out, but they certainly couldn’t run, so we are basically at the limit. And having said that, they have never dropped me in a 2-hour TT effort.” It would be different if he were to run a TT effort with the best runners in the world, like Eliud Kipchoge, for example.

To put some numbers on it, Froome and Thomas could be considered two of the fastest cyclists at a longer distance (though of course there is no competitive 112-mile solo time trial in cycling), and Wurf—who is arguably the best cyclist in our sport—only lost less than 1% of the total time to the duo. Compared to the fastest men’s Ironman run times of around 2:35, even the U.S. men’s marathon “A-Standard” of 2:15 (which 63 men in the U.S. alone ran in the previous trials period), that difference is more like 13%.

Obviously this gap will be different as triathletes still have to run off the bike, while triathletes only have to bike out of the water, but it does show a massive gap between world-class single-sport performances in biking and running when compared to world-class triathletes’ splits.

The next frontier will be people learning to run fast. The bike is pretty much maxed out, as is the swim.

Who Has The Chops?

Wurf’s profile sketch of the future Kona winner and run record-breaker would be someone who is a “very strong cyclist who can ride fast without it affecting them, and run like a gazelle. Right now they are all full-gas to go with me, and can’t run to their potential off that,” he said.

He believes this person is already among us, as he points out that modern triathletes are more professional than ever before. And the top athletes have the best support in the world—from both a training-coaching perspective and a technical one deriving from their sponsors. (Team Ineos Grenadier supports Wurf on the training and cycling front, while the Sub-2 team who helped Kipchoge is looking after him for the run.)

But the reason for Wurf being so close to world-class cyclists—and not to the best runners—could be down to running economy and anthropometric measures. And that’s also why the gap between the best triathletes in the world and the best runners may never be closed as well as with the best cyclists.

Fast Runners Are Fast For A Reason

“If you look at the best runners in the world, like the Kenyans and the Ethiopians, the reasons for being the best is due to their economy,” said Dan Plews, sports scientist and head coach at Endure IQ in New Zealand. Plews also happens to be the AG course record holder in Kona (8:24:36 set in 2018).

He says that at a given and equal VO2max (maximal aerobic capacity), the best runners’ ability to excel in comparison to their peers is mostly down to their economy (the energy required to produce a given workload measured in the amount of VO2 in L/min) and their body build.

“They are very small, very slender, with small calves, and very high insertion of the Achilles. All these things make them into really efficient runners,” he said.

On the other hand, Ironman triathletes need to swim and cycle, which results in different body shapes, with bigger quads and calves. These factors affect efficiency more, which is another part of the reason that the gap between the best runners in the world and triathletes may never be closed.

“If you take an efficient and a non-efficient runner, you can talk 20-25% difference in terms of economy, and that is the reason why people like Kipchoge are so much faster than anyone else,” Plews explained. “It’s not because they have this massive [aerobic] capacity. It’s because of their economy.”

On the other hand, in cycling, individuals are more constrained by their bikes, so the difference of VO2 required to produce pure power (without taking into account wind resistance) is smaller. “You can do everything you want in terms of aerodynamics. If you have enough money and know-how and equipment, everyone can get to the same level,” he said. “You can also improve your economy in cycling, but because you’re constrained and you’re clipped into a bike, you’re talking to 2-3% between the best and not the best.”

Then there’s the fact that Ironman triathletes always start the marathon with their glycogen stores partly depleted, slightly dehydrated, and with their muscle elasticity usually compromised after the bike (which also makes their distance per stride shorter).

The Crystal Ball

That said, even Plews agreed that run times in Kona will get faster. “I think getting close to the mid-2:30s would be amazing for the males. I don’t think we’ll ever see anything in the 20s. I would be very surprised if that would be the case. In a course like Kona, which is not flat but quite rolling, I can’t see anyone getting much lower than 2:35,” he said.

But on the women’s field, at least in the marathon, that may not be the case.

“I think the women’s mark is somewhat less likely to be improved upon than the men’s, at least by any appreciable amount,” said coach and author Matt Fitzgerald. “The reason is that women’s marathon performances in Kona went through a distinct breakthrough period relatively recently—the one leading up to Mirinda Carfrae’s existing record [2:50:26 set in 2014]. To me, this indicates that the men’s mark is softer and that men’s marathon performances in Kona are more ripe for a breakthrough period.”

When you think of potential male candidates for being able to run that fast in this generation, the mind goes to the past Kona winners: Jan Frodeno, who ran a 2:42 marathon in 2019 (already an improvement from his 2:45 set in 2016), and Patrick Lange, who holds the run-course record with a 2:39 marathon split set in 2016 (and the first man to run under 2:40 at Ironman World Championships).

To produce a breakthrough run and win, they would still need to hold a high power on the bike.

“I would expect that a 2:35 would be possible for someone swimming fast and also cycling fast,” Wurf said. “As far as going down in the 2:30, I guess it is for someone who is not that strong on the bike and looks after himself more and tries to run people down.”

Fitzgerald agreed that Kona’s faster overall time-splits will be more likely to come from speedier run splits.

“Nobody’s going to run 2:22 after swimming :58 and riding 4:40 to win in 8:00,” Fitzgerald said. “A 2:36 marathon in Kona would qualify as a breakthrough, and I think this could come on the heels of typical top-tier swim and bike splits without making anyone’s head explode.”

In both the male and female fields, that could happen by pure chance and as the combination of the right athlete “in the right shoes, in the right conditions on the right day,” Fitzgerald said. And if that happens once, it can easily lead to more performances of the same level, as the bar rises for every athlete.

That might not be too far down the road.

“I believe that, if faster men’s marathon times are indeed possible in Kona, athletes capable of achieving them have existed all along,” Fitzgerald said. “This is precisely why I expect sub-2:39 run times to become fairly common if they happen at all. I base all of these speculations on a general knowledge of how the phenomena of performance breakthroughs and revolutions have played out in sports historically.”