Six-time IRONMAN World Champion Mark Allen, who I worked with through most of his triathlon career, still holds the marathon record in Kona at 2:40:04. Keep in mind that back in 1989 the run split included the transition time, which for Allen was around a minute and 15 seconds. "It was a long transition," Mark told me recently. Being at the race myself, I actually do recall wondering what the heck was taking him so long. This would bring Allen's actual marathon time into the 2:38 zone.
Why has the men's record not been broken for nearly a quarter century? The Kona run course is arguably even easier today than when Allen set his record in 1989. With better bike gear, running shoes, nutrition and training information, not to mention so many great athletes who have entered the sport, you would think we'd have seen faster marathon times by now.
The Unique Challenges of the Marathon
It's not that swimming fast for 2.4 miles is easy, or that a 112-mile bike race is not demanding. For varying reasons, though, many triathletes deem the marathon the most difficult part of IRONMAN racing. Why?
For one, an IRONMAN race is a highly aerobic activity, one that requires only about 70 percent of one's VO2 max. Yet, despite this, athletes often train at intensity levels that are too high, and during the race simply ride too fast before they set out on the run.
Second, running enlists more muscle function compared to biking or swimming. "The run is where it's the most difficult to take in calories to sustain your effort, which makes it very challenging to keep your energy levels up at a fairly decent pace," Allen says. But what may be most important for running a great marathon typically occurs on the bike, before T2.
It All Starts On the Bike
Given these challenges to running, the most significant single recommendation for a successful IRONMAN marathon I can offer is to ride at a sub-max heart rate. By doing so, an athlete accomplishes two important and necessary feats:
Riding aerobically allows you to burn more stored body fat for energy during the bike. If you ride harder, you will probably burn less fat and more sugar, using up too much glycogen by T2—a problem that will catch up with you on the run. This is especially important on the ascents, when you will actually have to slow down to maintain the same max aerobic heart rate. However, descending allows you to ride faster at the same rate, more than making up for what is sometimes thought of as "lost time" (which it is not). In addition, one must avoid the temptation of keeping pace with others as they ride past—you'll get your chance to pass them on the marathon course (if not later on the bike).
Allowing your heart rate to guide your pace rather than the clock enables you to maintain a more consistent speed over the 112 miles of the bike course. Rather than slowing down and speeding up, this consistency in itself can improve your riding economy, saving energy for the run.
Allen, who applies these principles to the triathletes he coaches, calls this strategy essential. "Any faster than that on the bike and you start to deplete glycogen faster than the carbs can be replaced," he says. From an energy standpoint, it's your body's fat burning ability that ultimately carries you to the finish. Sure, the marathon is still the hardest part of your long day, but luckily, even the leanest body has sufficient fat stores—even for great back-to-back-to-back races—but only if you've prepared your metabolism. Getting in glucose during the race certainly helps, but a key focus should still be preparation—training the body to burn more fat.
Properly training your metabolism to burn more body fat will also allow you to ride (and run) faster at the same sub-max heart rate. Following are two steps to get you tapping into your fat stores on the bike.
Find Your Magic Zone
First, you'll determine your sub-max training heart rate. You'll then use this range for your IRONMAN bike, and for aerobic training, which will teach your body to burn more fat. While a lab evaluation is best, the formula below is an accurate option:
1. Subtract your age from 180.
2. Modify this number by selecting among the following categories the one that best matches your fitness and health profile:
- If you have or are recovering from a major illness (heart disease, any operation or hospital stay, etc.) or are on any regular medication, subtract an additional 10.
- If you are injured, have regressed in training or competition, get more than two colds or bouts of flu per year, have allergies or asthma, or if you have been inconsistent or are just getting back into training, subtract an additional 5.
- If you have been training consistently for up to two years without any of the problems mentioned above, keep the number (180--age) the same.
- If you have been training for more than two years without any of the problems listed above, and have made progress in competition without injury, add 5.
For example, if you are 30 years old and fit into category (b), you get the following: 180-30=150. Then 150-5=145 beats per minute. In this example, 145 is the maximum heart rate that develops great fat burning. Training above this rate rapidly shifts to burning more sugar and less fat for fuel.
Eat to Burn Fat
Next, consider how your meal choices affect your ability to burn fat. Refined carbohydrates—almost all flour and sugar products—can cause the body to burn more sugar and less fat during training and racing, while packing on more body fat, to boot. This is not the case during training and racing.
Burn more body fat, maintain a constant sub-max heart rate on the bike, and watch your IRONMAN marathon time come down to where you know it can be.
Sign up for an IRONMAN.