My friend Lauren looks like a gazelle as she sprints up the rocky stream bed of Ventana Canyon. Her long legs spring off the rocks, and even though we’re not here to run fast we can’t help speeding through the more technical spots in our Fivefingers. Trail running in the steep and rocky (and cactus-covered) desert comes with two gears, for me anyway: walking or hurtling through the momentum. I prefer the skill and holy-crap-I-just-missed-that-cactus-by-a-millimeter feeling of the second gear, personally. It’s more fun.

Lauren only started running when she got a pair of Sprints, and they’re the only shoe she wears out on the trail. We both agree that running shoes are too blocky; they get in the way and in my case cause me to turn my ankle a lot more often, due to the way they want to wobble on the tops of rocks instead of wrap around and absorb the edges. When you run the way Lauren and I are running–softly, striking on the forefoot–all the engineering that goes into pronation control and neutral heel strike on a running shoe is negated. Our feet have already landed in their own alignment before the heel taps ground in the middle of the stride; there’s not a lot that an arch support can do for you if you’re not really weighting it.

With this kind of stride, we’re really using the arch as a spring to bounce back with. One of my favorite researchers of human evolutionary biology (and yes, I have a few favorite researchers of human evolutionary biology), Daniel Lieberman of Harvard backs me up on this. There’s a great video put together by Nature in which you can watch people running in Lieberman’s lab, with shoes and without, and see the coinciding graphs of what the forces of running look like for the feet.

I find this absolutely fascinating. Folks who run barefoot (and this would be the same in Fivefingers) typically have a forefoot strike as opposed to a heel strike. With a heel strike you get a crazy spike in impact force as the foot hits the ground and comes to a dead stop while the body catches up, pivoting over the heel. In a forefoot strike the impact disappears as the arch and all its tendons, like rubber bands, absorb the energy and spring it back out on the toe-off.

Less shock to the body and a more efficient use of energy? These are very compelling reasons to run barefoot (or in Fivefingers, if you climate is very cold or very hot and rocky and covered in cactus spines).

And they make normally clumsy people (here I speak for my self more than my friend Lauren) run with the grace of gazelles.