The more niche you can get, the bigger of a fish you become in your pond. For example, it is much easier and much quicker to become an expert on bodybuilding for ectomorphs than it is to become a popular fitness writer.
Once you get some recognition within your specialized athletic niche you can then build off of that and grow into a more full-fledge general topic writer if you wish.
Contributor: Erik Bowitz, Editor of Skinny Yoked from skinnyyoked.com