I've often read that the effort of charging up a hill is usually offset by looser downhill running that usually follows. It doesn't seem to be the case for me.
When going up a steep hill, I fit my breathing pattern into the rythm of my foot strike. Once on top, I could be out-of-breath but still in the right tempo. If the top of said hill is followed by a flat road, I can regain my breathing quite fast by keeping a fast & short leg turnover.
However, the more downhill it goes, the longer I take to recup: I seem to be unable to adjust the fast breathing pattern I reached while going up into a (slightly) longer stride mode. I feel my breathing all over the place when going down. Not anymore in tempo with my foot strikes. I hate the feeling. Any suggestion ?