I've only ever understood heavy exercise to negatively affect ttc in how it can delay/prevent ovulation through causing too low body fat for ovulation and other hormone imbalances (exercise releases cortisol which acts counter to the fertility hormones).
So I guess exercise can affect implantation in a roundabout way: if it prevents an adequate uterine lining developing through putting your hormones off balance. But I highly doubt it could shake it out of place.
The uterus isn't a hollow organ, it is like a shrivelled collapsed little tube thing until you get pregnant and then it expands as it fills with amniotic fluid and, well, a baby. So it isn't like the egg is rolling around like a ping pong ball inside, erm, how about an inflated balloon, does that work?! More like one of those polystyrene balls from a bean bag, inside a used condom.... Wow I should be a writer. Basically I don't think it's possible but if it did happen, surely there's no way that particular egg would've made it into an embryo if it was that fragile.
I read about a female parachutist whose shut did not open properly and she slammed into a tree and in hospital she discovered she was pregnant, despite her broken bone she went on to have a healthy baby. This just proves how protected it is!
I was training for marathons while ttc. My consultant who was treating me for infertility categorically stated that running 50 or so kilometres a week would not impact my fertility. Turns out I was getting pregnant but miscarrying very early due to a polyp in my uterus, was to allowing the embryo to attach to my womb.