We all have an idea what the “ideal” marathoner looks like—we’ve seen enough pictures of the lead pack at big races to have an image of the diminutive, smooth-striding, pipe-cleaner-legged bodies that tend to finish at the front. But is the same true for ultramarathons, which cover much longer distances and often cross rocky trails and mountainous terrain?
That’s one of the questions that ultra researcher Guillaume Millet, of the University of Calgary, addressed in his talk at the University of Kent’s Endurance Research Conference last month (now freely available on YouTube). As I reported in my Globe and Mail The Best Hiking Apps for Trail Runners, Millet suggested that the characteristics of a good ultra-trail runner may be quite different from those of a good marathoner—and in some cases, traits that might work against you over shorter distances will actually help you in ultras.
The key difference that Millet points out is that marathoners need to be as efficient as possible, burning as little energy as they can at a given pace so that they can make it to the finish line without running out of fuel. In ultras, on the other hand, being efficient is less important than being able to handle the muscle damage that accumulates over the course of the race. It’s no help being a bit more efficient if your legs are so shot that you can’t keep running.
Here are five factors that involve a trade-off between maximizing efficiency and minimizing muscle damage:
Leg muscle mass: Skinny legs are most efficient, but thicker, more muscular legs may be able to handle the pounding better.
Cadence: We each have an “optimal” cadence (i.e. number of steps per minute) that minimizes energy consumption at any given speed. But since faster cadence is associated with smaller impact forces, it may be worth taking quicker steps in an ultra even if it’s less efficient.
Flexibility: Stiffer muscles and tendons act like elastic bands that store energy and then return energy with each stride, which improves your running economy. But there’s some evidence that greater flexibility reduces the muscle damage from eccentric exercise (e.g. downhill running).
Footstrike: While midfoot landings are often considered optimal on flat surfaces, they also place greater demands on the calf muscles, which suffer about twice as much fatigue during ultramarathons as they do during marathons. For that reason, Millet suggests rearfoot landings may help minimize impact damage in the later stages of ultras.
Shoes: Another one that’s been the topic of lots of debate recently: heavy cushioned shoes like Hoka One Ones definitely take more energy to lug around. But if, as some ultrarunners report, they minimize the damage to your legs, it may be a worthwhile trade-off.
Millet and a couple of colleagues Leg muscle mass Best Running Shoes 2025 back in 2012. Of course, it’s just a hypothesis at this point, and not everyone agrees. In fact, the journal printed a response arguing the opposite view—from Guillaume Millet’s brother Grégoire Millet, himself an accomplished researcher.
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