I copied this from another thread where I was exploring downhill running. The big insight I gained is that "running" downhill and "running downhill" are different activities and require different form. At a certain pitch, you need to brake. You can do so by slamming your heels down, as it sounds like you were doing, or you can "run" with "poor form". By that I mean you do the exact things you avoid doing on flat ground because they produce braking forces.
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I blew off my original plan this morning and tracked down a moderately pitched trail. Moderate enough that I could run the whole uphill at MAF, with some rollers, steeper sections, and flats. About a 1200 foot gain in about 4.5 miles. Easy footing, it looked barefootable, but I wore my Vapor Gloves to reduce the number of variables. Anyway, I played around a lot on the downhill. Only a few short sections were steep and loose enough to make me nervous about losing control so I had a lot of freedom. Running normally down hill felt easy but caused my HR to spike immediately.
Using some of the insights from this thread, I discovered several ways to modulate the braking force without sending my HR through the roof. Pushing my upper body slightly forward and my butt back slightly, landing flat footed with weight on my whole foot, and softening my knees gave me effective braking. The imagery of picking my feet up before they touched, pulling with my hamstrings, controlling a fall, and imagining that the surface was slippery all seemed to work. Changing my posture as before and dropping my hands down by my pockets gave me more braking force with no perceptible increase in effort. And finally, reaching my hands downhill and forward as though I was skiing or mountain biking gave me the most braking. By modulating these brakes, I was easily able to keep my HR in my MAF range all the way down while maintaining decent speed and control. Instead of my quads burning, I noticed that my glutes were getting tired. Interesting. But then they got a workout going up, so I really don't know how the braking energy actually got distributed. I need to do the same run starting with the downhill to get a feel for that.
So the theory about dumping energy by running "wrong" seems to have merit. Bending at the waist, flat footing, and softening my knees all reduced the energy return from my legs. Taking my arm swing away reduced the energy return from the counter rotation of my torso. And finally, reaching downhill deepened my stance while completely killing all rotational energy return. My balance was better and I slipped less often than I did when my response to a downhill was to push my hips forward, soften my knees, and go like heck. I've got a long way to go and a lot of experimenting to do, but thanks to all of you, I feel like I'm starting off on the right foot instead of flailing around. Thanks, everyone.
If you're going to give this a try, I should point out that the bend from the waist was very subtle until I reached down and forward. Subtle enough that I couldn't perceive my butt going back, although it had to have done since I remained on balance. It's amazing how much difference a tiny change can make.
