1-Working out shows fairly immediate results. Within a few weeks, you lose weight, see more muscle, run faster, etc. Writing? Even with the most consistent writing practice, results (in terms of noticeable improvement or getting published) are few and far between.
2-There's much more social support for working out. I have lots of friends who will accompany me to the gym or go out for a run with me. Writing is so solitary--which I love, but which also means there's no peer pressure egging me on, and I can't kill two birds with one stone by writing while I chat with a friend I've been meaning to catch up with.
3- Similarly, there are many more people in my life who will pat me on the (sweaty) back after a workout than there are who will cheer me on for finishing a page of writing.
4-Did I mention the immediacy of results?
All that said, I am *pretty* sure that if I committed more to writing, I would see more results. So, even without the guarantee I wish I could garner from the writing fairy, I am going to commit to a writing routine in August. I'm still working out the kinks of the program, but I'm sure it will be just as grueling--and hopefully satisfying--as the tri training has been.