Even Ultra-Endurance Athletes Need a Little HIT

You might never sprint during an Ironman or ultra-running race, but that doesn’t mean you can’t benefit from some HIT.

Ultra-endurance athlete running through the woods
Photo: Shutterstock.com

Logic would suggest that if you’re never going to sprint in a race, you will gain nothing by doing sprint training. Logic would suggest that if you expect to finish your target race in 12 hours, you should prepare by increasing your training volume or duration at your target pace. (Who needs Tabatas if you’re never going to break 15 mph all day long?)

Logic would be wrong. Regardless of the length of your race—even for a weeks-long race like Tour Divide—there are gains to be made from high-intensity training for ultra-endurance athletes.

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That’s a function of general physiology principles and, specifically, how our various energy systems adapt after different types of training. That’s a simple way of saying that a whole host of biological processes change in various ways when we train, including: mitochondrial density, lactate clearance, hydrogen ion buffering, vascular polarization, fat oxidation, cardiovascular stroke volume, neuromuscular recruitment, muscle fiber conversion, and the list goes on. Many of these are too complex to discuss in a short article. Instead, let’s focus on general principles.

As a reminder, we gain fitness through the process of supercompensation. When we hit an energy system with a bout of work, it creates damage, which kickstarts the repair process and can lead to supercompensation.

Some systems adapt to low-intensity work; for others, it takes high-intensity work above threshold. This complexity makes it difficult to find the right dose of each; if you were to try and train everything simultaneously, it could overwhelm the body.

On the other hand, if you only do a little bit of damage, your body is only going to repair it and build it back to the level it was at before. You take the “super” out of supercompensation.

“With the right amount, the body says, not only am I going to repair it back to where it was before, I’m actually going to make it better, I’m going to make it stronger,” says Trevor Connor.

So finding that right dose sometimes necessitates HIT, sometimes LIT, and sometimes a combination of the two. To find that dose, it’s helpful to understand “the box.”

Building capacity

Every athlete has a “fitness box.” If you raise the ceiling of that box, you also increase the area of the box. If your ceiling grows from 6 to 10 feet high, the whole box grows in size—there’s more capacity.

The ceiling is akin to your top-end fitness. You don’t raise your ceiling by training the duration of the event. You increase that top end through HIT work. As a nice bonus, evidence suggests that if you’re doing HIT work to improve your anaerobic threshold, you will also increase your aerobic threshold. The two will shift upward congruently.

“If you want to become a stronger, faster ultra-cyclist, you have to work your top end,” says Kristen Legan, the lead coach of Rambleur, which specializes in coaching gravel and bikepacking athletes. “When you think of your riding capabilities as a range, you have to improve your top end in order for that middle zone, where you’re going to spend a lot of time during your race, to improve. It doesn’t mean that high intensity is your main focus all the time, but working that is going to allow the speed at which you race to rise.”

Effectively, you are raising the plateau of that sustainable pace. In many ways, ultra-endurance events are like very long time trials: steady, sustainable pacing is the key to success. And many people make the mistake of training the duration of their TT events. That’s not going to raise the ceiling. You do that by pulling up from above, riding above anaerobic threshold.

Train for situational intensity

The demands of ultra-endurance events are different from other races, of course. While you might think that there will never be a reason to ride hard—only steady—that just isn’t the case.

For one thing, the terrain may dictate you ride well above threshold. For example, there may be a really tough climb with a stiff headwind—and the only way to climb it is to go all out. Add the weight of bikepacking gear to your rig, and you may feel like you’re doing intervals throughout the day, if the course profile warrants such surges in power. You might not describe it as a sprint, but your body doesn’t know the difference between racing for a finish line or going up a steep climb.

Being able to access higher power well above that endurance pace will come in handy. There will almost always be changes in speed and power dictated by the terrain or circumstances.

“As an ultra-athlete, it’s important to be a well-rounded athlete and have all the tools in your toolbox, to approach any terrain you may encounter,” Legan says. “So, while you may never sprint for a finish line, you may need to ride really hard to get up a hill without getting off to walk. Or you might have to dig super deep to beat a thunderstorm and get to a town at Tour Divide, for example.”

The start times of ultra-events also change the way they’re raced. A lot of them start before sunrise when it can be cold and dark, regardless of the season. There isn’t always time to do a proper warm-up. Still, whether because racers want to get warm or simply because there is a mass of excited people jockeying for position after the start, these races will often begin very fast.

“Doing some of your workouts where you have to jump straight into the intervals without your typical 20-minute warm-up…we have to teach our bodies just to be able to react,” Legan says. She will prescribe to her athletes an occasional interval session with virtually no warm-up to familiarize them with the feeling of jumping right in.

How and how much?

The favorable adaptations that develop from endurance training, whether HIT or LIT, have one thing in common: PGC-1 alpha. This master regulator acts as a signaling molecule to trigger adaptations.

There are four pathways that activate PGC-1 alpha, but the details are beyond the scope of this article. What is important to note is that research has shown that various training methods at various intensities all activate PGC-1 alpha, but the impact is different.

For the sake of this discussion, it’s enough to mention one pathway, the AMPK pathway. High-intensity training tends to activate PGC-1 alpha more through this pathway. The adaptations generated through the AMPK pathway tend to take place very quickly, in a matter of weeks. However, those changes also tend to plateau very quickly.

“You can produce rapid gains, but you’re going to see those gains level off, and you can keep hitting yourself with high intensity, but all you’re really doing is just maintaining form at that point,” Connor says.

This becomes important when you consider the average training plan of amateur racers. Most of us who live in North America fight against weather and daylight constraints in the winter months. When training for something like Unbound, volume is very important, but when it’s snowing out, it’s really hard to get outside for those 5- and 6-hour rides.

“I like having higher intensity workouts sprinkled in throughout the entire year. I do this with all of my athletes,” Legan says. “The ‘traditional’ periodized model with a heavy emphasis on base miles in the winter is traditional for professionals who have the means, the time, and flexibility to travel where it’s warm in the winter, or who have the time to spend outside in winter doing base miles.”

The high intensity training that she sprinkles in throughout the year ebbs and flows, rises and falls at different levels and at different times, but it exists in some form or another throughout the season.

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For those taking on multi-day events like bikepacking races, this leads to an important consideration: Deciding when to sprinkle HIT into your training plan. Remember that there will be an opportunity to gain fitness during the race. If you’re not racing for the win, you don’t need to come into the event firing on all cylinders. So plan to come in slightly under-trained so that you don’t burnout after the first five days.

“You don’t have to show up super lean, super fit, and ready to go. You want to be strong and resilient—more than race fit,” Legan says.

High-intensity training for ultra-endurance athletes is more physiologically and mentally stressful, so doing a lot of interval training in the final buildup for one of these races is not ideal. Rather, come in fresh, healthy, and rested—mentally and physically—so as to maximize your durability.

If you adopt Legan’s approach, you won’t need to add much intensity as you approach your target race. If you take a more traditional periodized approach, you probably only need to add several weeks of HIT before your target race, since those adaptations come about so quickly. Just don’t cram at the very end, hoping to “top-off” your form in the weeks leading into your big event.

Which HIT workout is best for ultra-athletes?

There are as many answers to that question as there are coaches. Tabatas? Sure. Four by eight threshold intervals? Yes, indeed. What you like to execute, and what you can confidently execute with quality, is in many ways as important as the type of interval you do.

For inspiration you can always check out the Fast Talk Labs workout library, but remember that quality and consistency reign supreme over complexity and specificity.