The author, Chris Case, is preparing to race Dirty Kanza 200 on June 2. This is the first installment of a series of articles he’s writing on the physiological and nutritional demands of ultra-endurance events like this, as well as the gear he’ll use in the grueling 200-mile gravel race across Kansas’s Flint Hills.
In 2013, in my first attempt, I completed Dirty Kanza 200, a grueling, absurd, fantastic, arduous gravel race across the Flint Hills of Kansas.
It was extremely evident was that my body was not built for 13.5-hour rides or 204.5 miles in the saddle. I knew this because after so many hours, and after consuming innumerable bits of a variety of food items in a plethora of textures and consistencies, and spending half of a day in a state of lonely, self-inflicted torture, I could feel, with an acute intensity, that my body had stopped having any kind of fun.
Indeed, I knew before I started DK200 that year that I was built for racing of a different kind: cyclocross. With its anaerobic accelerations and stabbing intensity, that glove fits, and I wear it. Alas, on a bit of a whim, I gave Kanza a try. Fortunately, I lived to walk again.
“Can my physical and biological mechanics adapt to the rigors of going long? It’s time to find out.”
So here we are in 2018. I’ve long since forgotten the torture that is 13.5 hours of racing. (Actually, no I haven’t.) I’ve started to gather the best gear for the task, including a 3T Exploro with an Enve 525 G wheelset built around a Saris PowerTap G3 hub.
But the real question is: Can my physical and biological mechanics adapt to the rigors of going long? It’s time to find out.
With the help of VeloNews’s resident physiologist, Trevor Connor, (and my co-host on Fast Talk, the VeloNews podcast on training and sports science) we are reworking my physiology to better withstand the rigors of a really long day at a significant pace. Hopefully, by understanding the transformation I’m putting my body through, you will better appreciate some of the most important concepts to building form for a race such as Dirty Kanza, or any ultra-endurance race.
Understanding my physiology
Key to the best training plans is a solid understanding of one’s heart rate and power zones. A lactate test in a respected physiology lab is the best way to identify those zones. I visited the University of Colorado Sports Medicine and Performance Center in Boulder to undergo a lactate profile test, in which lactate levels were analyzed in my blood as I rode progressively harder, above and beyond my so-called lactate threshold. The results of the test reveal the two key metabolic events that occur as we increase our intensity. The higher threshold, often called the anaerobic or lactate threshold, represents the highest power or heart rate that can be sustained aerobically. The lower threshold, called the aerobic threshold, is the point where blood lactate levels begin to rise. It is the point at which we begin to recruit fast-twitch muscle fibers. (More on those in a minute.)
From the results of my test, Connor surmises that what I suspected to be true about my physiology is all too real. I am not built, or trained, for ultra-endurance events. The process to convert me into a Dirty Kanza contender (or simply into someone who won’t have to completely empty every cell in his body just to finish) is going to take some serious reworking.
“Relatively speaking, your slow-twitch fibers are underdeveloped, but your fast twitch Type IIa fibers — the fast-twitch fibers that can act aerobically — are ‘hella strong,’” Connor said. “This is what makes you such a good ‘cross rider, where being able to use those fast-twitch fibers without building up a lot of lactate is a real benefit. But the underdeveloped slow-twitch fibers are why you’d really benefit from some slower, longer riding.”
“I am not built, or trained, for ultra-endurance events. The process to convert me into a Dirty Kanza contender is going to take some serious reworking.”
And by slower, longer rides, Connor specifically means spending a lot of time riding at my aerobic threshold (not to be confused with the more well-known “anaerobic threshold”).
Our aerobic threshold is a subset of aerobic endurance, the body’s energy system for pure, non-fatiguing work with oxygen. It is defined by the efficiency and strength of our slow-twitch muscle fibers and our heart’s ability to deliver oxygenated blood. Research of elite endurance athletes, led by Stephen Seiler at the University of Agder in Norway, indirectly suggests training at your aerobic threshold for several hours at a time raises the maximal power you can ride at without producing considerable fatigue. A number of top coaches and cyclists believe the same based on their personal experiences. For gravel racers who are often spending eight-plus hours on their bikes, this is a critical point where a key physiological shift takes place. Imagine being able to spend hour upon hour in a high-paced race setting and feeling just as fresh as when you started.
You guessed it: I am doing a lot of riding at or just below my aerobic threshold. I also spend some time at sweet spot intensities, and throw in some structured interval work because, as research has shown, working the different energy systems is complimentary. But it is very much polarized, with approximately 75 percent of my time spent below my aerobic threshold, 10 percent above anaerobic threshold, and the remainder between those two poles.
In essence, the riding I’m doing is about training my body to maintain homeostasis. An athlete’s body is constantly trying to maintain various physiological parameters within normal ranges. This is called homeostasis. When it comes to cycling, improving the ability to maintain homeostasis means improving the muscles’ ability to resist damage. Of course, maintaining energy stores is also critical.
“The number-one principle of physiology is that homeostasis drives almost everything in your body,” Connor said. “Your body is trying to maintain those normal conditions in the face of whatever insults you throw at it. And you can think of exercise as an insult. And a good way to think of fatigue is your body going out of homeostasis.”
So how do I improve my ability to maintain homeostasis?
Recruiting the right muscle fibers
Humans have three muscle fiber types: Type I (slow-twitch), Type IIa (fast-twitch), and Type IIx (also fast-twitch). Slow-twitch fibers work aerobically. Theoretically, if you continue to eat and drink properly, they can churn away indefinitely without fatiguing. Staying below aerobic threshold allows you to primarily use these fibers.
Type IIx fibers are used for the most intense efforts, and won’t last very long before fatiguing. In a race like Dirty Kanza, you might as well leave them at home.
Type IIa fibers are transformable and can work either aerobically or anaerobically. In essence, they can behave like a Type I or Type IIx fiber given the situation. As mentioned, for an endurance cyclist I have a lot of these fibers, and through the training and racing I’ve done, they have become fairly aerobic in nature. Therefore, I start recruiting them very early when riding, but I can last a long time while using them. Still, this is not an ideal situation because they are more prone to fatigue than the Type I fibers.
“Theoretically, if you continue to eat and drink properly, slow-twitch fibers can churn away indefinitely without fatiguing.”
Consequently, if I start using Type IIa fibers early on in a race like Dirty Kanza, I will see a lot of cardiac drift. In this phenomenon, at a given heart rate, power output will drop over time. It means that as my fibers fatigue, I’ll have to recruit more and more fibers to produce the same power, which will drive up my heart rate. Eventually, the rise will become unsustainable, and I’ll have to back off.
“The more you can rely on those slow-twitch muscle fibers, at those higher wattages, the longer you can go in Kanza at a pretty high intensity,” Connor said.
So what’s happening at a cellular level when I put in all these long, relatively slow miles? And why is it so important? The answer is both fascinating and complex. Ultimately, it may come down to the fact that the gains I make by riding at aerobic threshold are not limited as they are with high-intensity work. (Research indicates that high-intensity work is taxing, both physiologically and mentally, and an athlete can only do so much before it leads to fatigue or, worse, burnout.)
The benefits of riding at aerobic threshold include the ability to toughen the slow-twitch muscle cells themselves; they become more robust and can therefore work more powerfully and more effectively over longer periods of time. Strength training can also help here as well.
“Don’t underestimate the powers of these rides. There is much to be gained; it simply takes time.”
“They can withstand damage better, so you don’t end up having to recruit the fast-twitch fibers to take the place of any slow-twitch fibers that get too damaged to function properly over the course of a 12-hour race,” Connor said.
Another benefit to these aerobic threshold rides is that they increase the density of mitochondria inside the cells. As you may remember from high school biology class, mitochondria are the power plants of our cells. Slow-twitch muscle fibers with more power plants will, not surprisingly, last longer, and do so aerobically.
All this is to say that the training I’m doing is geared toward strengthening my aerobic endurance system — the primary energy system at use in a race of this type — so that I delay the use of the other secondary (supplementary) systems.
How does it feel to so often ride slow and steady? At first, I thought there could be no way I’d make significant gains by going so slow. It felt too easy. I’m certain others would feel the same. But don’t underestimate the powers of these rides. There is much to be gained; it simply takes time. The changes are also harder to notice because the benefits you gain aren’t put into practice on every ride. Eventually, as you improve the system and increase the sustainable duration, these rides become quite difficult.
“These rides beat you up in a very different way from intervals,” Connor said. “This fatigue is unpleasant, builds slowly, and takes a toll on your body. But you’re going to get a lot of that type of fatigue and strain on your body at Dirty Kanza, so there is a real value in teaching your body to tolerate it now.”
All in the name of teaching my body to maintain homeostasis.