Big Island Metrics: How to Taper for Your Biggest Race of the Season

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A runner at Kona

Over the past several years, as the popularity of Ironman racing has increased, so too has the availability of devices for tracking our training and racing metrics. As race day in Kona nears, what are the most useful tools for tracking how we’re doing and what to expect on race day? Having coached dozens of athletes across the Big Island’s finish line, I have learned that the following 10 metrics can make or break you on race day, regardless of your fitness. Although these metrics are specifically important for Kona success, they can be used for any Iron-man, especially those in hotter conditions.

Six Weeks Out

You should track these first two metrics as early as six weeks out from race day. This allows enough time for adjustment if they are not changing as expected.

Workout performance: The first thing that I like to track is something that can be used throughout the year, but becomes most important during the final six weeks before race day. Generally, each heartbeat is worth about three seconds per mile while running and approximately three watts on the bike. Within about a 10-beat span, you can use this rule of thumb as a calibration to judge your current fitness. For example, if you do one run at 7:45 pace with a heart rate of 140 bpm, and the next run at 7:30 pace with a heart rate of 142 bpm, you can adjust the second run by two beats, the equivalent of six seconds per mile, to compare the two runs. In this example, the second run would have been at 7:36 pace if you had run it at a heart rate of 140 bpm, and therefore it indicates an improvement of about nine seconds per mile. Of course heat, duration and terrain can have a significant impact, so always try to use similar weather and terrain when making this type of comparison. What you should find is that your fastest workouts are during the taper and race week. If not, maybe it’s time to consider more rest! Also, check out my free tool at  to better define your expectations and race-day pacing.

Body fat: This is typically a much better metric to track than body weight, as it mostly factors out fluctuations in fluid retention related to sodium and fluid intake. Body fat tracking is usually best done using skin-fold calipers, which tend to be significantly more accurate than digital scales. You can find calipers for less than $20, and they are very easy to use. Appropriate body fat goals are best determined with the help of a registered dietitian or a coach. If you could stand to lose a few pounds, keep in mind that a single pound is typically worth about three seconds per mile when running, one minute over the course of a 70.3 and two minutes in an Ironman. But leaner isn’t always better. The objective is to hit your race weight during race week, not sooner. You certainly don’t want to overdo it!

Two Weeks Out

The next three metrics will begin to prepare you for an optimal performance. You should consider them two weeks out from race day.

Perceived sense of self: While this comes in many forms, the top indicators that you can home in on include feeling rested, self-imposed pressures, and senses of confidence and satisfaction in your preparations, both mentally and physically. This is an excellent time for you to use appropriate race-day imagery and establish positive race-day cues, focusing on how your day should unfold, and preparing yourself to manage the inevitable setbacks that an Ironman athlete is bound to encounter. Don’t hope something won’t happen; assume it will and make sure you have a tool in your race-day toolbox to deal with it. Part of this is the development and imagery of contingency plans, to combat any number of potential snafus. If you work out and practice in your head “If I flat, then I will . . .” you’ll be best prepared to manage the situation if it comes up.

The key with this metric is to make it just that: a metric! Many athletes understand this concept but few formally assess where they fall on the spectrum as race day approaches. I suggest you sit down and formally assess yourself in this area, honestly and objectively. Write down the pressures you are feeling and separate those that are self-imposed from those that are real. Write down things that you hope won’t happen and develop race-day tools to fix them.

Hydration levels: This is paramount in any hot race, not just Kona! Arriving during race week in a dehydrated state will put you in a position that is very difficult to recover from. After months of preparation, putting yourself behind the proverbial 8-ball is inexcusable. Making this a primary focus two weeks out from race day helps to make sure that there is ample time for any necessary corrections well before you even pack your bike.

Urine color is the easiest metric to ensure that your hydration levels are where they need to be. Always aim to see urine that is a very light yellow, or nearly clear. Understand that significant amounts of vitamin C may skew urine color. To remove subjectivity, I recommend using a hand-held refractometer to test your urine’s specific gravity to estimate your hydration level. Refractometers are a great tool for keeping you honest, as the constant accountability ensures that a water bottle is never too far away. If you live and train in a hot climate or have any issues with remaining hydrated, I strongly suggest having a refractometer on hand. They can be found for as little as $200, a fraction of the price of not having one.

Overnight heart rate: For it to be effective, heat acclimation should begin at least two weeks before race day. Within that time, one good metric to track the progress of the acclimation is average overnight heart rate. Typically, as an athlete begins to acclimate to the expected weather conditions, this overnight average will begin to settle down to pre-acclimation levels. Be sure to establish baselines before starting the acclimation period, and make sure that during acclimation you sleep in a warm environment with very little air-conditioning.