What Does It Take to Win Kona? – A Physiologist’s Perspective

To this point, after recently crunching some numbers on what it would take for Lance to win Kona for an upcoming article (stay tuned), I was left with the realization that the more powerful the motor that you’re dealing with, the more important economy becomes. In my last piece on Kona qualifiers I concluded that it takes a very fit dude with better than average fuel economy, that is, the ability to generate a good amount of energy from fat. When taking it to the next step and looking at winners on the big island, we are left with very, very fit dudes with a freakish ability to generate energy from fat.

Tim Noakes, in his book Lore of Running, talks about the “metabolic impossibility” of ironman racing. He concludes that in order to run a 2:40 marathon at the end of an ironman, fat oxidation must occur at a rate of 1.15g (10kcal) per minute. He also concludes that these rates of fat oxidation are double what he has seen for the elite runners in his laboratory!

Based on what I have seen, I would more or less agree with these numbers. Elite short course athletes typically exhibit similar fat oxidation to Kona qualifiers, that is ~5kcal/min. This is because functionally, while a useful adaptation in terms of tolerance to training load, this physiological quality is not limiting in a performance sense. Things like VO2max, threshold and movement economy are much more important for these athletes. However, the limiters shift once they decide to “step up a distance.”

For a 75kg athlete with a good bike position (FA=0.39m^2) to go 4:35 in Kona on a day with average winds is going to take ~270W. Assuming normal economy numbers, this equates to an energy output of over 1000kcal/hr! To get off the bike and run at 4min/k pace (2:49 marathon pace) is going to take even more ~ 1200kcal/hr! So, over the course of an 8:20 day, we are looking at energy outputs approaching 9000kcal! Considering our Kona champ is only starting with a best case scenario of ~3500kcal worth of glycogen and are getting ~2000kcal from drinks/gels/etc. along the course, this leaves him at least 3500kcal short, with only eight hours to generate it. Or, put another way, he needs to generate in excess of 7.5 kcal/min from fat.

While I haven’t had the pleasure of testing a Kona champ as of yet (open offer stands), I have had the chance to test ironman athletes across the spectrum from back of the packers to top age groupers to top pro’s and there is a strong trend towards these numbers. The fastest athlete that I’ve tested, an 8:17 ironman generated the magic 7kcal/min from fat oxidation. Our average athlete generates less than 3kcal/min!

If we were to follow the same logic as what I used for the Kona qualifier article, and assume that this requisite level of fat oxidation occurs at 60% VO2max, we would conclude that our prospective Kona champ needs a VO2max of ~86 ml/kg/min. However, I don’t believe this to be the case.

Another key adaptation that we witness, the further up the ironman ranks that we go, is the ability to generate high levels of energy from fat across a broad intensity range. In other words, while most athletes will have their peak fat oxidation rates in or around 60% of VO2max, our pro ironman athletes will have theirs continue up to, or in some cases beyond, 70% of VO2max.

While there is a difference in total fat oxidation across the board, a perhaps larger difference can be seen in the breadth of intensities over which these high rates of fat oxidation can be maintained. This means that very well-trained athletes can “get by” with lower VO2max numbers in the realm of 70-75ml/kg/min. Or, for the sake of real world comparison for a 75kg athlete: 5K speed of ~15:00 and an FTP of ~350W.

While there are a number of ITU athletes currently racing the circuit who fulfill these criteria and a much larger number of endurance athletes worldwide who have the required aerobic power numbers, the ability to fuel these high levels of output for very long periods of time is the distinguishing ability when it comes to professional ironman racing.