Fitness when horseless?

As I cope with my six weeks of no horse, I am trying to stay fit for riding. And I'm wondering how J. is doing on that front...she is a little bit of a hard keeper, and when I first got her she was skinny. (See photo!)

By the time I left for the states in June, after more than a year together, she was looking GOOD. Nice neck. Nice butt! Even, sometimes, a nice smile. Plus that shiny avocado oil treatment coat.

Now I worry we'll both have a lot of make-up work to do in August. We may need our own version of bootcamp fitness, someone to yell at us while we work our abs, glutes, cores, etc.

So, right now, I'm trying to avoid the worst by running (about 3 miles four times a week), doing push-ups (I'm up to 20!) and crunches (except I hate crunches, so I'm not going to tell how many).

Are there secrets to staying in shape for what is, after all, a pretty weird and specific form of athletic endeavor...especially after 50? Would love to hear from other riders! And how do you keep your horses fit when you can't ride?