Thank you John Sandford, James Lee Burke, Michael Connelly, P.D. James, Lee Child, Alan Furst, Tana French, Patricia Cornwell, Stephen King, and John Grisham.

I am 77 years old and in excellent physical condition, according to my physician. This would not be possible without you.

For this reason, I am also deeply in debt to Scott Turow, Henning Mankell, Nelson DeMille, Jo Nesbo, Arnaldur Indridason, Dennis Lehane, John le Carre, Martin Cruz Smith, Laurie King, and Daniel Silva.

For the last 20 years, these prolific writers of mystery and suspense novels have kept me dutifully churning away for an hour nearly every day on treadmills, elliptical trainers, rowing machines, and stationary bicycles.

Though I occasionally venture to new authors, they are my stable of writers whose abundant outputs assure that at least one of them always has a new book that I haven't read.

For most of my adult life I was a runner, rising early and getting out on the road in the lemony light of dawn. There was a sensory aspect to running — the sounds of birdsong and church bells, the silky aroma of flowers and the reassuring smell of wood smoke, and the sights of scurrying squirrels and hawks riding the thermals overhead.

Then, as I approached 60, one of my knees resigned in protest. The surgeon warned me I had two choices — "stop running, or limp for the rest of your life."  But luckily, he added, I could continue to work out on the less-jarring equipment in a gym.

So I bought a treadmill and installed it in my basement. After a few days, I realized it wasn't the same as running. The big difference? There was nothing to see, smell, or hear. Just a blank wall, the faint hum of a furnace, and the slight aroma of cleaning products. The minutes went by like centuries. When I finally stepped off, I was stone-eyed with boredom.

But then I recalled staying up an entire night reading Peter Benchley's suspense classic, Jaws, because I was too engrossed to put it down. It was then that I realized what could be a potent exercise motivator — page-turning books that I listened to rather than read. Soon I was stepping on the treadmill eagerly to hear what happens next in my book. Some mornings I actually stay on overtime — and not to increase my exercise minutes.

For an hour a day, nearly every day, I'm exercising mind while exercising body.

Audiobook CDs are expensive to buy, but hundreds of good titles are available for free at most public libraries. And thousands of titles are available from Amazon's, which has monthly memberships as low as $15.

You can, of course, listen to any good book. I like to read Faulkner and Hemingway, but as gym companions they come up short. A successful gym book is one that makes you look forward to your next workout. Though I also listen to books when I'm driving, some of my gym companions have rules to only listen in the gym.

A lot of Americans have made New Year's resolutions to get more exercise, and many of them will join gyms. But the exercise failure rate in America is very high. How high? Franchise gyms like Planet Fitness have built into their pricing plans the fact that most people who enter membership contracts to join will not show up very often.  They consider the no-shows their best customers. If everyone showed up five times a week, there wouldn't be enough equipment to accommodate them. One company reported that its 500,000 members showed up 29 million times a year –or about five times a month.

These grim statistics have led health gurus to search for ways to get people to the gym more often, and some employers are offering financial incentives.

What's wrong with a good mystery?

William Ecenbarger is a former Inquirer writer who reads and works out at the gym or in the basement of his home in Hummelstown.