Adding content to existing page vs. adding a new blog post

Add new posts, you can cover a lot more ground, SEO-wise

It's unlikely 100 word articles will do much on their own in the long term so, add some commentary here and there, flesh them out with images, diagrams, videos, etc.
Explain why x does x and therefore tones your thingy's.

Add some health warnings about doing it wrong, busting a gut, etc

Throw in some humour, and personality, make it interesting, that type of content gets shared.

You want to make your content the 'go to' resource for whatever it is...

Mix and match, interlink, stick in a few quotes from subject authorities and celebrities?(attribute any quotes with a link) (don't go mad) and add your own comments to the quote.

You page will soon be full.

The list on this subject is endless...


3/5/10/20/50 Fitness Tips For...

Cyclists
Your Dog
Fat People
The Disabled
Seniors
Diabetics
Truck Drivers
Taxi Drivers
Office Workers
Your Hamster
Your Cat
Working Moms
10 Stone Weaklings

etc...

Forget about Big G for now, write for people and promote elsewhere.

I'd suggest adding your own extra flare to the tips and expand each tip from 100 words to at least 500 (1000 if at all possible). Then create new blog posts for each of the tips, be sure to use different types of keywords without keyword stuffing. Tim3's advice on using quotes, pics, vids and commentary to expand your content is a very good one.

Another thing that is always good, is to give an example of either the benefits of the tip or the negative outcomes from not following the tip (and personal examples if possible).

Adding new posts only helps if you are consistently doing it.

If you are willing to consistently add new posts then it is much better for SEO because you naturally get more backlinks ,organic traffic, and google spiders crawl your website more.

This again assumes that you are targeting keywords correctly and you are consistently backlinking.

If you are not going to consistently be adding new content then it is not going to make a much of a difference either way.

Adding a new blog post is improving its performance to the targeted audience and sending a signal to the search engine that your blog is a hub of information.