Actually, I found this post from Scott. I think that explains everything! Never mind then!
“Scott Johnston ON JANUARY 27, 2019 AT 2:34 PM #16259
Downhill running (and skiing) present special training challenges for mountain athletes. There is a specific type of strength required to be successful on long events with lots of descent. The main quality needed for both these is muscular endurance. Sounds familiar right. Thats also what is needed to run or ski up hill fast for a long time too. But the ME we are speaking of for down hill is needed in muscle fibers that are higher force/faster twitch fibers than you are using when going up hill. It is hard to recruit these FT fibers because the loads have to be very high.
The muscle damage that occurs in long fast descents will eventually cause many runners (and skiers) to slow even on the uphill due the release some nasties into the blood. It is not as obvious on the uphills because the runners revert their very well trained pool of Slow Twitch fibers once on the climbs again.
What we here at UA do to combat that is to employ a special strength (muscular endurance) training system to build that specific type of muscular endurance in those FT fibers. Luke Nelson credits his 8th place finish in the brutal Tor d’Geant race last September to these workouts. You can achieve similar gains with a lot of fast down hill running. But with much higher injury risk and much higher training loads. This is discussed on our recent strength training series. https://uphillathlete.com/strength-training-for-the-mountain-athlete/ . That ME circuit described is one very close to what Luke used and also forms the base of the Mike Foote Big vert training plan https://uphillathlete.com/mike-foote-big-vert-ultra-run-training-plan/
We’ve found this to be super effective with some of the negative side effects of lots of fast down hill running.