Blog Post Labels

I have a question for anyone out there that might know the answer. I've only just started adding labels to my posts...not sure why I start it two years ago, anyway, I didn't.

My question is, if I go through a bunch of posts now and add the labels to them will that send out a whole whack of emails to my subscribed readers or do they only get the one email from the original post that I made? Same with Google Reader, will it add a ton of new posts in their Reader if they subscribe to my blog that way? Does that make sense? lol :)

I'm just trying to make it easier for anyone looking at my blog so that they might be able to navigate around a bit better to look at things that are of interest to them.

Thanks in advance for the help! :)

Hugs,