If you're riding on steep stuff it really doesn't do knees any favours.
I propose that if any-one trots out this shite they get a 24 hr ban for being an idiot. One last time, SS isn't going to kill your knees… 🙂
Will you need stronger legs? well sort off. Up any decent hill your heart rate will go straight to L3 but only really on steeper hills, and surprisingly it's mostly about balance rather than al out strength. personally I think my upper body gets a far bigger work out, as you end up sort of "rowing" the bike up hills. Rest of the time (flat and DH) you'll be pretty much in your recovery zone.
So its slower on hills, and the flat and roads…
whats the plus side…?
You could say that about all bikes though really, right? Don't compare SS to regular riding it won't stand up to the scrutiny. Without getting too bollocky-****-shite about it, it's just a different challenge to regular riding, You know? It's physical, it's about challenging one-self.
Try it, you may like it, you may not, up to you