Ah, in our hearts, we're runners.
It's just safer to call yourself a plodder when you're talking to some bloke who looks faster than you (balding, skinny, legs like spiders etc) because then you don't have to admit that your best 10k time is over an hour, because at the mere mention of the word 'plodder' he loses interest and doesn't actually ask. Or is tactful and doesn't ask (if he's a nice bloke). If he does ask, he's probably a plodder too.
It's a code, really . . . .
;-)