If you're a runner you've heard it before in some capacity: Running is essentially jumping from one foot to another, you're never on both feet together, so your cross-training should reflect this.
This statement, while probably overused, does hold a lot of truth. There are plenty of great exercises for runners with both feet on the floor, but utilizing a unilateral stance will always emphasize stability, go along way to protecting your knees and be especially helpful for a trailrunner's preferred variable terrain.
In my humble opinion, the Pistol Squat is the granddaddy of all unilateral leg exercises. If you can do a full range of motion Pistol (as shown in the video), you're strong, stable and flexible. As a runner, you're going to be balanced and WAY less prone to injury. I think all runners should be doing Pistol Squats and that holds doubly true for the trailrunner.
The problem with the Pistol is usually where to start. If you can't do a full range of motion squat, sitting your butt all the way down on top of your heels, you need to start there. Keep both feet on the floor and work on a full range of motion. Just the act of improving your squat motion will have a ton of other beneficial side effects, like increased flexibility and joint elasticity, but it will also start to show you the benefit of this position (a position we evolved using and completely went away from as a species with the invention of the chair (total speculation but it can't be that far off)). Dr. Steve Gangemi (the sock doc of Trailrunner Nation Podcast fame) even advocates spending as much as 15 minutes per day down in that position meditating. Its good for you. I promise.
After you've mastered the full range of motion squat, it's time to move on to the Pistol. There are a number of different ways to modify this exercise to make it easier. In my experience, using a box/bench/chair to sit on is the easiest, most effective way to learn the Pistol and quickly progress. Simply stand in front of a chair, pick up one foot and hold it in front of your body (just like in the video) and then, in as controlled a manner as possible, slowly lower your butt down to the chair, sitting down fully before returning to a standing position using only the single leg.
Try to complete your entire set (6-12 reps) without putting your off foot on the floor. Let your hip stabilize at the top and bottom of the motion. As it gets easier, you can work toward not committing weight to the chair, just touching lightly before raising up. Then, once you've developed the strength and stability for that, lower your surface. Keep moving it down until you can remove it all together.
This movement takes time to master. It is difficult, engaging and will have you ecstatic over even the smallest of gains. It will make you a much better, more balanced runner... and, if nothing else, you can use it as a party trick. Give it a shot.
As always, we'd love to hear your feedback!