I think your title is the biggest roadblock. It's descriptive, which is good but it's also generic. There are a lots of stories with running tips out there so you need a bit more to lure in the reader. I'd take a cue from your opening and do something like, "Tips to Go From Hating Running to Finishing a 5K"

The topic is fine. The great thing about medium is you don't need to write about popular topics you just need to write (and title) in such a way that over time the people interested in your topics find you.

The larger the publication the more I think the title matters. You need to stand out.

One other tiny comment. I would have linked to Nike Run Club. You noted that you have no affiliation so that base is covered but as a reader, I love having links because I'm lazy and don't want to cut and paste into a search engine. Also linking to outside sites can have a small positive impact on where google ranks you.