When the weather is pleasant, there's absolutely no reason to confine your workouts to the gym. With all the high-tech advances in running and climbing and biking machines, we tend to forget that the real thing lies right outside our front door, and at a substantially lower cost than a gym membership. Your own body weight provides more than enough resistance for a good strength-training program, and with a little ingenuity and imagination, you can fashion dozens of workouts at any level of difficulty, from beginner to boot camp. The folks in the military have been doing it for years.

You can easily make your own basic boot camp routine by walking (or running) for a bit then stopping to do any of a dozen quick exercises that require little more than your own body weight and perhaps a park bench or a tree. Then resume walking (or running) till you get to the next pit stop, where you perform the next exercise.

Here's a sample intermediate program. You can make it easier by extending the walking time between exercises, doing fewer pit-stop exercises or doing fewer reps of the exercises themselves. If you're an advanced exerciser and up to the challenge, making it more difficult is a cinch: Faster runs between pit stops, extra sets and reps during. The time spent walking (or running) between pit stops is given just for the sake of example. You can -- and should -- adjust it to your own needs.

Warm-up: Walk 5 minutes

First aerobic period: 5 minutes brisk walk or slow jog
Pit stop: Walking lunges. Step forward, extending your right leg in front of you. Bend your knees, and lower your body toward the floor between the back and front legs. The back leg will bend and the back heel will come off the floor. The front leg will be bent to a right angle, with the knee never going in front of the ankle, remaining directly in line with the ankle. Come up and switch legs, bringing the left leg forward, and repeat. Do 10 "switches."