Ultramarathon Training – 80/20 Endurance

Ultramarathon Training

Rob Krar competes in—and often wins—100-mile ultramarathons. When training for these events, he never runs farther than 35 miles. From a purely mathematical standpoint, a 35-mile training run might seem like inadequate preparation for a 100-mile race. But there’s a reason Rob and other champion ultrarunners cap their training distance at or near 35 miles: The human body simply can’t adapt to anything longer. You will gain no more endurance from covering 40 or 45 miles in training than you will from covering 35, give or take, so there’s no point. In fact, it’s actually counterproductive to exceed 35 miles, because as fitness returns diminish (and ultimately peter out altogether) with increasing run distance, injury risk increases. Put another way, beyond 35ish miles, running ceases to be training and becomes punishment.

There’s not much scientific validation for this claim—it’s a difficult thing to validate scientifically—but we can be quite certain it’s true. Athletes have a way of figuring out what does and doesn’t work before scientists prove it. If you’re an ultrarunner and you want to optimize your training, you’d be well advised not to wait for science to catch up and instead follow the example of the likes of Rob Krar by capping your long runs around 35 miles. And if you’re significantly slower than Rob (and nearly all ultrarunners are), you should mix in some hiking with your running whenever you cover this distance and avoid doing pure runs lasting longer than 4.5 hours or so, which is about the amount of time it takes a Rob Krar to jog 35 miles.

That being said, I do believe there are psychological benefits associated with running farther. In particular, it gives you a taste of the suck you’re going to experience on race day. But because runs longer than 35ish miles are punishing, it’s best to attempt them only within the context of races. For example, if you want to be at your best both physically and psychologically for a 100-miler, consider doing a 50-miler eight to twelve weeks before it.

There are certain things you can do in training to further boost your endurance without defying the 35-mile rule. I’ve already touched on one of them: mixed run/hike sessions. By inserting hiking segments into a long run, you can spend upwards of five hours on your feet without crossing the training/punishment threshold—assuming you’ve built up to it.

A second option is back-to-back long runs (e.g., 20 miles on Saturday followed by 20 miles on Sunday). This method allows you to experience running on tired legs in a way that isn’t as risky as an extremely long single run. The magic happens in the second run of the two, which you will start with a certain amount of fatigue in your legs from the prior day’s run. I like to do single long runs and back-to-back long runs on alternating weekends during ultramarathon training.

Fasting offers another way to enhance the training effect of long runs. When you withhold carbohydrate in particular before and during long runs, your muscles are forced to rely more on stored fat to supply the energy they need. When done with some regularity, so-called depletion runs increase the overall fat-burning ability of the muscles and thereby increase endurance. In addition, when you run long in a fasted state, your muscles reach a deeper level of glycogen depletion than they would in a normal long run. This triggers genetic adaptations that improve aerobic capacity.

Finally, if you enjoy riding a bike, you can use what triathletes refer to as brick workouts to build endurance without defying the 35-mile rule. A brick workout is a bike ride followed immediately by a run. For ultrarunners, the bike portion serves to prefatigue the muscles for the ensuing run, but in a nonimpact manner, allowing you to get as tired as you would from a run longer than 35 miles while sparing your legs from the punishment that would come from actually running that far.

When I trained for my first ultramarathon (the American River 50 Mile Endurance Run) over the winter of 2015-16, I had an Achilles tendon injury that prevented me from doing any training that was faster than marathon pace, give or take. Fortunately, I had no limitations on how far I could run, and took full advantage of this freedom by completing individual training runs of up to 37 miles.

When I arrived at the start line of AMR50 on April 2nd, I was definitely fit, but not as fit as I would like to have been. A crucial piece was missing; my legs felt the lack of faster running in a way that’s hard to define. This feeling was validated not only by the ensuing race, in which my performance was humdrum, but in my next ultra, which I won following an injury-free buildup that including regular doses of moderate- and high-intensity work.

Many ultrarunners voluntarily eschew such work, having little taste for it and assuming it makes no significant contribution to success in low-intensity races that require many hours to complete. But a recent study says otherwise, further validating my experiential sense that fast running is a vital component of effective ultramarathon training.

Conducted by Spanish scientists and published in the European Journal of Sport Science, the study involved 20 “ultra-endurance runners” with an average age of 40 years. For 12 weeks, half of these subjects followed a “threshold” training program in which two-thirds of total training time was spent at low intensity and the remaining one-third at moderate intensity (i.e., roughly lactate threshold intensity), while the other half followed a “polarized” training program with an equal overall workload but in which 80 percent of total training time was spent at low intensity and 20 percent at high intensity. Both groups lost body fat during the 12-week training period, but only the polarized group showed improvements in running economy and in running time to exhaustion.

Do we conclude from these findings that ultrarunners should never do any training at moderate intensity? Of course not. The purpose of the study was to compare the contributions of moderate- and high-intensity running to fitness development within the context of a mostly low-intensity training program, not to identify the optimal way to train for ultramarathons in the real world. But what we can conclude from the study is that ultrarunners should do a significant amount of training at high intensity.

If this finding seems counterintuitive to you, it’s probably because you don’t fully understand how high-intensity training works. The purpose of doing fast workouts is not, in fact, to get faster. Rather, it is to enable you to use more of the speed you already have in races, regardless of distance. High-intensity running does this in a variety of ways, including by increasing aerobic capacity, improving running economy, and even elevating pain tolerance. You only have one body, and it is this one body that is altered by any sort of training you do. Thus, even though a set of hard intervals on the track doesn’t look much like a 100-kilometer trail run, it will help you perform better in such a race by altering your body in beneficial ways that complement the benefits of longer, slower training runs.

This is why the 80/20 ultramarathon plans that I’ve just created for TrainingPeaks include speed work—not a ton, to be sure, but enough to give you better results than you would get from a training plan that did not require you to test your higher gears. There are eight plans in total: four levels each for 50 miles/100K and for 100 miles. Check ‘em out!

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