I would agree with ^this. My first thought, when reading this, was "Thats cool! I would like to find some ways to get exercise at work. But why should I sign up for a (potentially) spammy email list, when I can probably just google 'office exercises'?"

raivo:

I don't think you need to explain that you won't spam us. If you decide to give an example email, make sure an "Unsubscribe" link is clearly visible somewhere in the email. That will help build trust.

I would also be curious as to where the exercises are coming from- you may have included this info in the text, but I didn't read it because it was too long...

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?

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.

^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.