Tread carefully, take Baby Steps. Long strides are fine on flat terrain, but when going up or down, shorten your stride. Bending your knees deeply, as you do when taking big steps up or down, works the large muscles and your joints harder than bending your knees more shallowly. (Think: what’s harder, walking up and down a stairway one step at a time, or two?) In the same way that long switchbacks in a trail ease its difficulty by lessening the path’s angle, while you’ll take more steps by shortening your stride, you’ll work less hard than if taking big steps up or down.
A side benefit of this technique when going downhill is that you’re less likely to slip and fall, because you land with each foot more directly below your body weight, rather than ahead of you. The reason most falls occur walking downhill (we rarely fall when walking uphill), is that when stepping up, we land with each foot almost directly below our body – a balanced position – whereas when walking downhill, we land on a foot that’s out in front of our body, a position that’s more off-balance.
Source: The Big Outside