There may well be clean athletes in Russia training outside of the state-sponsored program. Problem is, the anti-doping system in Russia is also non-compliant with the WADA code, so there's no way of having any clue as to which ones are the clean ones.
While we're at it, I'd chuck out all competitors in all sports from countries with non-compliant testing. If that means a generation who miss out on the Olympics, then so be it, if that what it takes to start having some confidence in clean competition again. When will the next Olympics be when there isn't this wholesale re-distribution of medals years after the event?
Yes, I know that compliant testing is no guarantee, but it's a start.
Shona, from my experience it's not the running per se that causes problems, but combined with phases of rapid growth there can be joint issues, particularly ankles and knees (the obvious ones I guess). Put simply, the grow so quickly that tendons don't keep up, causing pain when running. That was the problem my boy had anyway - no problems running parkrun regularly when he was younger, but when he was 11 he started to get knee pains. Stretching helped, but the long-term solution was to lay off running while his growth was quickest. He's fine now, he's 13 and taller than I am so hopefully no more growth spurts!
Caveat - the parkrun he does is off-road, so a bit easier with impacts than one on tarmac. I'm not sure if that made it easier when he was younger - most of the youngsters seem to have a better running style with less heel strike than many of the adults!