I suspect the racist tag was applied because stereotypically white men are slower runners than black men. But as far as racism goes that's... not to mention that it's a white guy talking about himself.

While I'm generally happy with the position that white guys can take it, I think it's still racist to imply white men are slow, whether one is a white guy or not.

It's not really racist to say something like that especially when there is strong supporting evidence.

Racism is where you advocate treating somebody differently because of these differences. So it would be racist to say "White men are too slow therefor should be banned from taking part in the olympics"

No, it isn't. It is not at all racist to acknowledge the physiological differences between different ethnic groups. It is well established that a higher leg-to-torso length ratio correlates with faster sprint times. Conversely, a lower leg-to-torso ratio correlates with faster swimming.

Racism has nothing to do with facts. It is all about promoting hatred based on superficial differences.