[raivo]

Joe and olegious thanks for the feedback - good points!

I will add the sample email, and a paragraph about why you should sign up.

To quickly answer it here, you should sign up because an email will serve as a reminder for you to exercise.

Now, I'm not sure how to explain (and be believed) that I won't spam you?

[khafra]

Just promising not to spam and not to share user information will do a lot; you don't need complicated explanations. If you have a record or reputation with any particular community, it probably wouldn't hurt to reference that.

[JoeCortopassi]

^this. I wasn't trying to insinuate that you were a spammer. Just that this could be a common perception when someone goes to your site.