After decades of hiking, I still don't like my downhill technique and I haven't figured out a better way. Slow and smooth works for a bit 'til my quads burn. Stomping blows the knees even quicker.
I read of the Sherpa-Step some years ago and it totally changed how I approach uphill stairs and steep inclines. No such luck for downhill.
One thing I have noticed is that a large drop in the shoe exacerbates the downhill problems. I've since 'downgraded' my shoes and that does lessen the toe cram.
I've put in 350 miles in the last few months, improving my endurance, and consequently the problems don't start until after 20 miles or so. Still, I can pound steep uphills at 30 miles, but have to slow waaay down on the equivalent descents.
Any good suggestions? Reading?

