So in part 1 post : run leg vs bike leg at Ironman I explored the difference between a flat-out time trial on the bike vs an Ironman bike using data from 100 mile TT records and Kona Bike times. I then looked at this alongside world record marathon runs vs Kona marathon runs. The final key comparison was looking at the cycle difference compared to the run difference. Essentially it looked like there was a bigger % difference between a solo run compared to an Ironman run, than there was between a solo TT compared to an Ironman TT. These differences might be expected when you consider the run comes after the bike and in an Ironman, which means more depleted nutrition stores. It’s also harder to take in nutrition on a run than on a bike and you have to take on a fair bit on the last leg of an Ironman. A Kenyan running a 2.04 marathon can likely get by on a few sips of sports drink maybe a gel at most. The Ironman runner begins in a huge calorie deficit, needing to take on carbs, and with legs smashed from the cycle. What about for shorter triathlon though, where the bike is having less impact on the run?
Even the Kenyans take on some carbs …Image by PhotoRun
There’s a lot of aspects that change when we move to thinking about an olympic distance triathlon. Running a 10k at the end of a 40k bike and 1500m swim is not nearly as demanding nutritionally. The total time will be well under 2 hrs and the majority of the elites won’t take any nutrition on during the fast 10k run. Just thinking about the running style of an Ironman pro vs an East African running fresh on the road, there’s a huge qualitative difference in their run styles. I don’t imagine that difference as much when I think about a pro cyclist and a pro Ironman on their bike. But, here’s the thing. I don’t think of that difference so much when I see Alistair Brownlee sticking down sub 30 minute 10k’s compared to the East African runners. In fact, Alistair seems as close to a Kenyan runner as he is as close to a Pro cyclist. I know it might sound bizarre to compare the qualitative style of running/cycling between triathlon to non-triathlons, so let’s see if we can look at this more quantitatively i.e. their race times.
Alistair Brownlee in Bejing …Image by rocky arroyo
It just so happens that last weekend the British time trial records of Alex Dowsett for both 10 miles and 25 miles were smashed in a single weekend by Marcin Bialoblocki who rode a cool 16.35 (36.16mph) for 10 miles on the Saturday and 44.04 (34.03mph) for 25 miles on the Sunday. Biaboblocki was annoyed to not go under 44 mins for 25 miles, saying he felt a bit tired from the previous days 10 miler despite taking 25 seconds of Dowsetts previous 25mile record. Ignoring the 10 miler, the 25 mile distance is rather close to the olympic distance bike which measures 40k (24.85 miles). Alongside this, we have a weekend of Alistair Brownlee taking part in a non-drafting olympic triathlon in Beijing, so there’s definitely some recent race times to look at.
Marcin Bialoblocki from One Pro Cycling team
Now when I looked at flat-out bike times compared to Ironman bike times I found that there was a 16% increase in total time for the Ironman bike (3hr.18 vs 3hr.50, (Stadlers IM bike time was actually 4:18- we did some adjustments to bring the IM time down to represent 100 miles and not 112)
If we apply a similar 16% increase to the 44min, 25 miles of Bibloblocki, we ‘re roughly looking at 51 minutes for an olympic distance bike. Alistair’s bike at Bejing was 55.57 (26.65mph) with only Cameron Dye having a faster bike split (by 10 seconds). However, Beijing has a climb in it and these guys are clearly capable of faster than this when the bike course is flat. With the Brownlees main race times set in ITU drafting events where they can maintain a higher speed by drafting with other cyclists in a group, we don’t really know what Alistair is capable of on a flat course but we do have Cameron Dye’s cycle time from the much flatter Hyvee cycle course in 2015. He rode a 52:21 (28.48mph), which would represent a 19% increase- not a massive difference to the longer bike, and considering the estimations we’re using, within the ‘acceptable error limits’. (nb. It remains 19% if you adjust the distance so it is 25 miles, not 24.85).
Cameron Dye on his super fast Ventum bike
There was an estimated 28% difference between the marathon record at Berlin and the Iron Man run record for in Kona. We could lower this % difference both on the bike and run if we were taking the fastest ever IM times, for instance from Roth or Austria but Kona was the focus. Moving back to look at Olympic distances, Leonard Patrick Komon holds the road 10k running record, set in 2010 in the Netherlands. His time, 26.44 is an average 4.18 min/mile pace. The olympic distance had a 10k for the final leg with Alistair Brownlee arguably the quickest runner in the sport. However, at Bejing Allistair only ran 35:54, which is really below cruising speed for him. Had he needed to run 5 minutes faster to win that day, he probably would. There’s also the small addition of 700 steps in the Bejing run leg so it’s not the best course to use for estimates here. Alistair regularly runs sub 30 minutes in ITU, but of course, the bike is drafting which can give some rest. For anyone who watched the Olympics, it was clear to see that they smashed it out on the bike. Post interview, Allistair said the run wasn’t particularly fast as 3-4 of them had really hammered the hilly bike course. He still ran 31.09 including time to celebrate. Let’s conservatively say he can run 31 mins off a hard non drafting bike. In this comparison, the flat road 10k is only 16% quicker than the triathlon 10k. To summarise, the difference in run splits is smaller in the olympic distance compared to the iron distance when looking at the % differences between solo and triathlon. We also see an interaction which is best shown on a graph:
Figure 1: Comparing Ironman distance and Olympic distance – Each blue circle represents the difference between a flat-out bike and a triathlon bike. Each red circle represents the difference between a flat-out run and a triathlon run.
If you’ve kept track of this and the multiple comparisons we’re making haven’t confused the hell out of you, then so far so good…
Essentially what the graph is showing is that the difference between a flat-out bike TT and a Triathlon non-drafting bike TT does not change massively between Ironman distance and Olympic distance. On the other hand, the difference between a fast road marathon and a triathlon marathon is far different than a fast 10k and a Triathlon 10k. The comparison is based on estimates along the way but I’m willing to bet that should a study conduct a range of data from these distances, they would get a significant interaction like the one shown in figure 1 above.
So why the difference between these distances? I would say that it’s primarily the running and nutrition which will make a big difference. When you’re racing olympic distances well under 2 hours, you don’t need to take on nutrition on the run. On the Ironman marathon you’re totally depleted of carbohydrate stores and need to fuel all the way through. Running too fast prevents you from absorbing the energy from your gels or sports drink. There will also be a fair bit more fatigue in the legs from a 112 mile bike compared to a 24.85 mile bike. What I think the graph is really saying, is that the event time may not affect the bike so much as it will affect the run, and that’s due to our difficulty with replacing energy on the run. Additionally, training your body to be more fuel-efficient is more important for long distances like Ironman than it is for 2 hour Olympic races.