Will running, not racing, one ultra end my 5k career? I'm looking at doing the JFK 50 Miler.
Usually I do some track stuff in the spring (15:30 5k)
And fall half marathon or marathon (1:11, 2:32)
I'll take 2-3 weeks off from running after the 50 miler.
If i run this, will it hamper my ability to run a fast 5k in the future? fast 800?
It will not kill your speed. I began running ultras at 22 y.o. in 1991 and have run everything from 50 milers (including JFK) through multi-day races since then. I'd run 4 - 5 ultras a year and many other shorter races as well. I ended up getting my PR's at 5 km (15:27) - 1/2 marathon (1:09) in 1997 - 1999 after several years of running many ultras. I think the key is to keep doing speedwork and short races. One ultra, and even several well-spaced ultras, will not kill leg speed for 5 km and up. Not sure about the 800 though.
yes it will turn all your fast twitch into slow twitch and you will be unable to run any distance without stopping for real food and taking a walk break while listening to motivational speeches on the iPod
the good thing is that all your co-workers will think you are real fast now