It is well known that the performance of athletes who suddenly move to a location at a higher altitude than they are used to will suffer; when sports events such as the Olympics are held in a high altitude location, athletes often move to the area much earlier in order to adapt.
The question I haven't been able to find an answer to is: How big of an altitude difference is significant? E.g. Will a sprinter who lives and trains at sea level feel any different competing at 200 - 300 m above sea level?