Photo by Jay Prasuhn/EnduraPix.com

With the Ironman racing season upon us, this is a perfect opportunity to walk (or should I say run) through an Ironman run pacing strategy. Specifically, we will be taking a very close look at Caitlin Snow’s pacing from this past year’s Hawaii Ironman. This is a perfect run pacing strategy to look at, because it was not only executed on an extremely hot day but resulted in a 2:56 run split—the second-fastest in the race’s history. (Click here to view her pace and heart rate file from race day.)

As a triathlon coach (and specifically an Ironman coach), I have developed many racing strategies for Kona. The execution in this particular example, however, is one of the best that I have ever seen. Notice that Caitlin’s heart rate was kept very well under control during the early portion of the run. Although we used perceived exertion, pace, and heart rate to pace the day, the latter was the primary pacing metric because the day was expected to be so warm. In hot racing conditions, heart rate can be used to account for potential heat accumulation, where a strategy based on pace may not. Heat accumulation will typically result in a dramatic decoupling between pace and heart rate. For example, heart rate will increase through the opening miles of the run, though pace slows or remains the same. This is indicative of an athlete who is accumulating heat more quickly than it’s dissipating. In most cases this will cause stomach bloating and an eventual unraveling, due to heat-related stress. When this occurs, the athlete’s only real option is to slow the pace and allow the system to rebalance itself.

Proper pacing can turn you into the envy of the marathon course.

Heat accumulation WILL force the body to slow. If not done voluntarily, the slowdown can be drastic and devastating to a race. Voluntarily slowing the pace can be a very difficult concept for many type-A triathletes to wrap their minds around, as they are often hard-wired to maintain some pre-determined pace no matter what. As a result, the athlete will typically continue to accumulate heat until it’s too late, and then be forced to walk. Conversely, heart rate-based pacing in hot environments allows the athlete to identify the warning signs of heat accumulation and adjust the pacing accordingly.

View the original file

Learning what we have about heart rate-based training, the general objective is to always maintain a steady heart rate throughout the entire run, and/or have it rise only during the final 10k. Of all the possible metrics that can be used to assess an athlete’s race, on the whole, the run heart rate file can provide the most valuable information. Any negative issues that may arise on race day will typically cause the heart rate to decrease throughout the run. I know that this may seem counterintuitive, as most athletes think higher heart rates signal explosions. On the contrary, a true explosion is typically the result of the peripheral system being so beat up that it’s unable to stimulate the heart rate.

Let’s consider a few examples: poor nutrition, over-pacing the bike, going out too hard on the run, and porta-potty stops. Each of these (or a combination) will result in a falling heart rate as the athlete gets farther into the run. If an athlete’s nutrition fails, they will be forced to walk later in the day. While walking, the heart rate is down at a pedestrian level—much lower than it should be, and almost definitely lower than at the start of the run. What you see in Caitlin’s file is a very steady heart rate through the entire run, and even a slight increase in heart rate during the closing miles. This is very difficult to do in Ironman racing and comes as a result of a perfectly executed day! Caitlin’s nutrition, and her pacing during the bike and the early stages of the run were spot on, resulting in this flawless heart rate file. By the very same token, the previous year’s heart rate file started out very high, decoupled from the pace during the first five miles, resulting in a bloated gut and difficulty with nutrition. Caitlin was accumulating heat too quickly. Unable to keep her heart rate up, and watching it drop after mile 10, she ended up about 13 minutes off of her expected pace—a result that we were both disappointed with.

Ironman is a peripherally limited event. The length of the day causes the muscles to become more and more fatigued, making it increasingly difficult to stimulate heart rate. A well-developed racing strategy should aim to maintain a high, steady heart rate, even as the race progresses. The goal should be to avoid doing anything during the earlier portions of the race that may cause the heart rate to drop during the run, particularly in the final third. Those who do this best will have the best race, relative to their abilities. Unfortunately, most athletes get caught up in pushing much too much wattage early into the bike. This fatigues the peripheral system by setting the heart rate bar much too high; two effects of this are stomach distress and a peripheral system unable to stimulate the heart rate through the whole run. Proper pacing, on the other hand, can turn you into the envy of the marathon course, passing all of those “lost souls” on the Queen K as you head home from the Natural Energy Lab.

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Jesse Kropelnicki is an elite/pro level triathlon coach who founded QT2 Systems, LLC; a leading provider of personal triathlon and run coaching, as well as TheCoreDiet.com a leading provider of sports nutrition. He coaches professional athletes Caitlin Snow (visit her blog here!), Dede Griesbauer, Ethan Brown, and Tim Snow, among others. His interests lie in coaching professional triathletes using quantitative training and nutrition protocols. You can track his other coaching comments/ideas via his blog at www.kropelnicki.com.