If you're like the typical Washingtonian, you spend at least an hour a day in your car. You may not think of your auto as a fitness center, but those long commutes, maddening traffic snarls and endless carpools can provide a surprising opportunity to tone your muscles -- and maybe relieve a little stress.

Besides, if you're doing some simple exercises in the car -- even just while waiting for another red light to change -- you're probably not snacking, a less benign pastime for many drivers and their passengers.

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Of course, car exercises aren't a substitute for the minimum 30 minutes of moderately brisk activity, such as walking, advised for all adults. Workouts in the car are isometric, or stretching, so they don't challenge the heart and cardiovascular system. They must also be done with common sense so as not to distract from driving.

But these surprisingly simple exercises can help strengthen core muscles that are important for the back. They can tighten pelvic floor muscles that help prevent incontinence and may help improve sexual function. They can also relax neck and shoulder muscles, which can help improve posture and alleviate tension.

"Instead of sitting around and doing nothing while you're driving, you can at least do a couple of things that can give you more energy and revitalize you," notes Canadian physiotherapist Maureen Hagan, who has just been named personal trainer of the year by IDEA, a group with 20,000 fitness and health professionals.

Hagan has developed exercises for her clients to do in the car and uses them herself to help stay awake, alert and less stiff on long drives. The beauty of these exercises is that they can also be done at your desk. Some can even be done at meetings that require you to sit for hours -- without anyone noticing.

"I have to bite my tongue a lot in meetings," Hagan laughs. So she relies on these exercises to help keep her from saying things she might later regret. "They relax my body and my mind," she says.

Here's how you can turn tedious commutes, traffic jams or hours spent sitting in the office into opportunities for some isometric exercises and a few stretches. Except where noted, do these exercises three to five times every 15 to 30 minutes.

Start at the top. Do a posture check to counteract the driver's slump (which also occurs at your desk). In the car, sit up straight, trying to "grow an inch" taller by bringing your shoulders back. Lift your head so that your upper spine is erect and in more of a straight line. Retract your chin so that your ears are directly in line with your shoulders. Hold for 30 seconds while breathing in and out. Do a set of five to 10 reps.