It’s one of the hardest kinds of running. You may think running up the hill was tough, pumping your arms, shortening your strides, and breathing hard. But what’s tough about uphill running is the level of effort, which is the kind of challenge one accepts in exercise. You expect to have to put in a hard effort, at least from time to time.
What’s waiting for you once you crest that hill, on the other hand, is a whole different kind of difficult that may be much harder to deal with. The impact that so many runners find it so difficult to manage safely and comfortably, and which can lead to runners’ knee pain in particular and other injuries as well, is much greater when you run downhill. If your relationship to impact is at all tenuous you’re going to feel very uncomfortable and even unsafe and you’ll probably instinctively hit the brakes to deal with it. That means reaching your feet out in front of you, overstriding and, footwear permitting, heelstriking to a possibly exaggerated degree to slow yourself down. It feels protective but it also feels lousy since it pretty much maximizes your impact and the toll on your body and also slows you down, which is not what most runners want.
But what else can you do?
The answer is simple: bend your knees more.
Bending your knees keeps you from overstriding, placing your feet closer to your center of gravity and preventing a jolt of impact shooting up into your body through your heel and leg. You use your leg more like a spring, absorbing impact by bending, while also lowering your body.
When you run downhill, each footfall is lower than your toe-off was. So with each step you have to lower your center of gravity a bit below where you started. You could do this when you’re in the air, by dropping like a ton of bricks out of the sky onto your next footfall, or you could do this in stance, lowering your body as you pass over it and creating a trajectory of movement for the next toe-off that goes down to the next step rather than up in the air.
This also shifts the work towards the big muscles of your thighs and hips and away from the smaller muscles of your feet and lower legs – particularly important if you’re barefoot or in minimalist shoes, so that you don’t try to do the job of absorbing the extra impact in your feet and calves instead.
Absorb that impact by bending your knees and shifting your hips and you’ll be able to keep rolling (so to speak) down the hill without losing too much momentum or spending too much effort, which will have a nice payoff if you run races. You may even begin to feel like you could lean downhill and accelerate a bit, and start to see downhill running as the funnest, rather than hardest, kind.