I think it's ok as long as you have a nice sports bra on and you're not posing in a slutty way. I mean, I've definitely posted 'naughtier' selfies than that lol. So come on!
I follow Ellie Goulding (one of my fav artists) and she posted a selfie of herself in a sports bra and it got loads of likes and stuff.
If you think about it, people wear a lot less on the beach and stuff, so how is Instagram or whatever you are using any different?
Selfies are meant to be a bit about showing off, so if you've got it flaunt it babe!
