Although I was used to running about 30 minutes a day, I knew that it would take at least an hour of walking to achieve the same exercise benefits. Now an hour of walking can seem like an awfully long time if you are doing laps on a track. But I found 60 minutes of exploring different walking trails in the state parks passed very quickly. The varied terrain, the beautiful trees, shrubs and rock formations, the birds, squirrels and rabbits kept my attention focused on the environment rather than on my watch.

While trekking the state park certainly was enjoyable, I was initially concerned that I would not receive much conditioning benefit compared to my running workouts. I was pleasantly surprised to find that a fast walk up and down the undulating trails provided an excellent exercise session. This was particularly true when I ventured off the main paths onto more challenging secondary trails. Taking my dogs with me greatly increased my probability of exploring less traveled parts of the parks.

Of course, trekking on uneven terrain requires proper footwear, with good support and stability. Well-designed running or walking shoes are highly recommended for enhanced safety and function.

Due to the longer period of continuous physical activity, you would be wise to carry some water, or plan your walk to take advantage of the fresh springs located in some park areas. At the very least, be sure to drink some fluids before and after your trekking session.

Woods provide wonderful settings for exercise, except when there is snow on the ground. During hot weather, shaded wooded trails provide protection from the sun and a cooler exercise environment. During cold weather, the trees offer a natural windbreak so that chilling winds are much less problematic.

Basically, the only drawback to woods-walking is travel time to and from the nearest park area. With shorter winter days, this may not be practical on weekdays. However, it should not be too difficult to take a woods workout on the weekends. You may even want to share a ride with a family member or friend who would like to be a walking partner.

Once you are ready to begin a walking program on the trails, you may need to use your watch for a training guide. Unlike your block on the track, you are unlikely to know the exact distances you are covering on the trails. To progress gradually and systematically, time your walking segments, as well as your overall training duration. That is, check your times at various sites along the trail as a guide to your present walking pace. As you gain fitness, you can quicken your pace to reach your checkpoints in progressively less time.

As your fitness level improves you can increase the cardiovascular conditioning effect by using an interval training approach to your walking workouts. Interval training is essentially a means for alternating higher effort and lower effort segments of each training session. For example, you may walk at a fast pace for 20 minutes, followed by a slower-paced walk for 10 minutes, followed by another faster-paced walk for 20 minutes, and finish with 10 minutes of slower walking. This protocol offers a full hour of continuous walking, but in a more interesting and challenging manner than a steady-paced excursion. In addition, the two faster-paced segments provide greater cardiovascular conditioning benefits. Of course, the two recovery walk segments make the workout more enjoyable.

Although you may prefer longer walks, an hour of interval walking is certainly sufficient for improving your physical fitness and enhancing your aerobic capacity. However, you may consider taking a few minutes before and after you walk to do some warm-up and cool-down exercises. Before walking, try a few half-squats (knee bends), a few side bends, and a few arm circles, all done in a slow and controlled manner. After walking, perform some stretching exercises to loosen muscles that may have tightened during your workout.

Begin with the standing calf stretch by leaning against a tree with your feet flat on the ground. Bend forward just enough to feel some tautness in your calf muscles, and hold the stretched position for about 30 seconds.

Next, stretch your hamstrings muscles by placing one heel on a tree stump, large rock, or the bumper of your car and bending forward slightly until your rear thigh feels taut. Hold the stretched position for about 30 seconds, then repeat the procedure with your other leg.

Finally, stretch your lower back by sitting on a tree stump or large rock, grasping your knees with your hands, and pulling your torso forward/downward until you feel a mild stretch in your low back muscles. Hold the stretched position for about 30 seconds, then sit up slowly.

This program of warm-up, walking and cool-down should ensure safe and effective park workouts. Just remember to watch where you step, and keep track of your travels so you can find your way back to the car.

Wayne L. Westcott, Ph.D., is fitness research director at the South Shore YMCA in Quincy, MA., and author of several books including the new releases Building Strength and Stamina and Strength Training Past 50.