It’s the first day of November which means we’re just over 3 weeks out from Ironman Cozumel - my first go at the Full Distance. Preparation for this race really started in January this year with a 3 to 4 month-long focus on increasing my VO2 max, all with the intention of increasing IM power/pace as much as possible later in the year.
With no Full distance experience to draw on and the probable extreme conditions (heat, humidity) in Cozumel, I want to make sure that I have a solid game plan for the race. From what I’ve heard and seen over the years, it seems like poor pacing, nutritional issues, and overheating are the main killers in the Full distance (these often go hand in hand). So, to best prepare myself, I did what any science-loving athlete would do; go to the lab (Kinesis Integrated) and do some testing with physiologist Jared Berg here in Boulder, Colorado!
In this article, I’ll walk you through the exact testing I did, how I’ve used the results in training, and how I’ll use them in racing. I hope you enjoy!
Why did I test?
As I said, I have no race experience over 4 hours. Despite never having any real nutritional issues in a Half distance, it’s clear that glycogen management is critical over 8 hours of racing. Further, I imagine that doubling the race time gives a lot more opportunity for heat to build up in your body. Finally, finishing on the podium of a 3-something hour race requires “real” racing; head to head competition that pushes you out of your limits for extended periods. From watching countless Full distance races, I’ve seen plenty of examples of athletes “letting the race go” at some point, only to come back stronger in the last 2 hours and run themselves right back into the mix. Knowing my own physiological limits is probably wise.
What did we test and how?
This testing was nothing out of the ordinary when it comes to lab testing. To sum it up, I did a step test on the bike and run, sweat rate testing, and sodium loss testing. As a little add on, I did 10’ at IM race effort after the last stage of the bike and run to see how my metabolism would shift back (or not) to baseline after going above LT2 for 5 minutes.
During the step test, Jared recorded VCO2, VO2, lactate, HR and intensity. With this, he could calculate how much substrate was used at each intensity (carbs and fat) as well as a lactate curve paired with HR. To estimate sweat rate, I weighed myself before the 1 hour of riding and after the 1 hour (the lab setup was in a warmer room with no fan…not super scientific but definitely semi-representative of Cozumel conditions). For rate of sodium-loss, Jared used a cool little device that measures sodium concentration from a sweat sample.
What were the results?
This is a secret :) Not really. The results were good in the sense that my metabolism is indicative of a good performance over a long distance race. Below are the substrate oxidation rates for reference. You can see that fat oxidation is fairly high at low intensities and remains relatively high for an extended time (especially on the run). This probably reflects a decade-plus of endurance training as well as a decent diet (no snacking on Haribo late at night) and proper training intensity distribution (prioritizing high fat oxidation rates for most of my training). From this data, I estimate that a safe IM power for the bike is around 225 watts. This clearly isn’t high enough to be competitive - more on that later. For the run, we see that fat oxidation remains high up to around 6:18/mile (3:54/km) with carb oxidation remaining reasonable at that pace. From this, it seems possible to me that I could run this pace for an IM in fairly hot conditions.
For sweat and sodium loss, the result were easy to work with. I lose around 800mL sweat/HR and 1000mg NA/HR. Not too much and easy to plan for.
How will I use the results In training and racing?
I’m going to bullet point this so it’s faster to read.
Where do I need to be? From past results, I figure I need to ride ~ 4hr15’ to make the podium. For me, this will require ~ 235 watts avg (knowing your cda helps to calculate this).
Where am I? From the testing, I think 225 is safe. This gets me ~ 4:18…. Too slow.
So, I need to increase IM power ~10 watts over the course of 6 weeks. Definitely possible.
How? Increase fat ox a bit and decrease CHO ox a bit
How? Long rides around 170 watts and intervals between 215-250 watts.
I predict I will be able to do 235 watts and achieve the 4hr15’ split with enough glycogen left in the tank to run at ~4:02/km (2hr50’ marathon).
To stay fueled, I’ll drink ~750mL/HR with ~120g CHO/HR and 750mg NA/HR.
Maybe I will blow tf up and have a nice walk through downtown Cozumel. I’ve done this before in the 70.3….. not the best way to spend your morning in Mexico. But! Maybe this testing (along with plenty of training) will help me race to my potential and walk away (walking AFTER the race!) with my held high and a nice (?) first experience with the REAL triathlon distance under my belt. Follow along on November 24th if you want to see how it goes :)
Where you can find Jared
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