Lest you swear off all forms of formal exercise until January, consider this: Researchers at McMaster University in Canada have found that short, high-intensity workouts have nearly the same muscular and cardiovascular benefits as longer periods of exercise. The key to making the most of shorter bouts, says personal trainer Nicki Anderson, owner of Reality Fitness in Naperville, Illinois, is giving it all you've got.

"By doing a mixture of whole-body exercises and cardio with no rest in between, you can get a great workout in only 15 minutes," she says. We worked with Anderson to put together a workout built on basic moves -- no fancy techniques or equipment required. All you need are comfortable clothes, a pair of sneakers, and a few feet of clear floor space. And if boredom is a concern, we've set the workout up like a takeout menu; choose one exercise from each category in whichever order you like best.

Choose your moves: For this workout, you'll complete three 5-minute circuits, for a total of 15 minutes from start to finish. First do 30 seconds of cardio (run in place with high knees, do jumping jacks, or jump rope), then select one exercise from each category -- lower body, core, upper body -- to complete in the remaining 4:30. Complete two more circuits right away, choosing a new combination of exercises each time.

In half the time it takes to watch an episode of "The Office," you'll burn calories, improve circulation, work up a light sweat, and enjoy a halo of energy for the rest of the day. But perhaps best of all, "You'll feel better about yourself because you've accomplished something," Anderson says, which may be more than you can say about your holiday shopping.

Come to a plank position with hands directly under shoulders. Bring one knee at a time into your chest, alternating quickly as if you were running.

With feet shoulder-width apart, toes forward, and hands behind head, lift chest and engage core. Squat and jump, lowering through heels (not just toes), and land carefully.

Step forward into a lunge on the left leg, then step forward (or up onto a stair) with the right. Pull the left knee up and hold for a few seconds. Lower the left foot (off the step), then step back with the right leg into a deep lunge. Alternate (10 reps per leg) for a total of about 1 minute.

Start in plank position and transfer weight onto your right hand for side plank, stacking your feet, and hold for 5 to 10 seconds. Roll back into plank, then shift into side plank on the opposite hand, lifting through your arm, core, and hip on the left side, keeping your body in line. Switch sides 5 times.

Lie face-up with hands behind head, legs lifted 45 degrees. Lift head, neck, and tops of shoulder blades off floor. Be sure not to pull on neck. Bend left knee in, reaching across with right elbow. Switch. That's 1 rep; do 20.

Lie on your right side with knees bent and hips stacked. Wrap your right arm around your waist and place your left hand on the floor in front of you. Push into the floor to lift your torso up, straightening your left arm as much as you can without locking your elbow. Bend elbow to lower to the floor. Do 10 to 15 reps per side.

From hands and knees, straighten legs to come into Down Dog, with hands slightly wider than shoulders. Bend elbows out to the sides and straighten arms to lower forehead toward floor and back up.

Keeping arms close to your sides and parallel, press down and up, like a push-up, with elbows bending straight behind you (not out to the sides), isolating the triceps. You can also do them on your knees, as shown.