It's a frivolous takedown notice, it happens all the time.
Under the DMCA, the takedown system heavily favors the accuser. They are not required to provide evidence unless the accused disputes the notice. To challenge a takedown requires providing your name and street address to the accuser, which circumvents the anonymity of your online accounts, so people are reluctant to do so. And there is no effective punishment for filing false notices either.
Live sporting events are not copyrightable in the US (see NBA v Motorola). Generally, if you hold the camera, you own the video, unless you signed a contract stating otherwise before attending the event. Organizers often try to make statements to the effect that "we own all video taken of this event," but they have yet to try to use that wishful thinking in court and would fail if they did. Youtube rejected it in the NASCAR crash video incident a couple years back.
There are other issues, like copyrighted images captured by the video, such as logos and ads. But as long as those are incidentally captured, i.e. not really important parts of the video, they are well within established fair use practices. Commercial use is more complicated but is not a copyright issue.
If you challenge the takedown, you will probably win, but runner's pace will know who you are.
One other thing about youtube is they have contracts with major corporations that allow those corporations to require takedowns for other than copyright reasons. I doubt runnerspace is one of them, but if it were NBC or something, and you had made video of a meet they had broadcast, they might have leverage to force it off of youtube.