So what does physical exercise have to do with writing a book?
Regular exercise will accomplish two benefits:
1. You will have more energy to write.I'm not going to tell you what exercises you should be doing--this is not an exercise blog--but I can tell you that power walking helps me. It's simple and can be done anywhere. My only expenditure: a pair of good walking shoes.When you raise your metabolism, you also increase your energy levels. Also, sitting at the computer all day can make you sluggish and even drain your creativity, so the 30-45 minutes of daily exercise will pay off.2. You will maintain your weight better.Writing is a very sedentary activity. If you plant that butt on your chair for hours on end without compensating for "butt spread," the pounds will creep on and the spare tire around your middle will inflate. I know this from personal experience ;=)
I have a personal in-home treadmill (1997 model), which helps during inclement weather, but if you can't afford to buy expensive equipment, then walking at your local indoor mall can be an option.
As I said, my personal exercise program might not be what you need or want to do. If nothing really appeals to you, simply unplant your rear from your chair every few hours and just walk around your house and stretch.
My advice to normally sedentary writers: Keep your exercise plan short, simple, and stupid--and secondary to your goal of writing that Great American Book.
If not, your book might end up being about your trials and tribulations in preparing for a 500-mile marathon.