Mix it up.

Nope, not your workout. Try mixing up your heart rate during a workout.

That's the latest buzz from fitness experts, who tout interval training [1], or workouts that deliberately vary the heart rate to burn more fat and improve cardio performance.

The idea is to get the heart pumping, then work extra hard and get the heart rate to soar for very short bursts of time (say, one minute), and then decrease that intensity for a bit longer (about four minutes). The push-recuperate cycle gets repeated several times during the workout. This way, the exerciser can alternate between an all-out effort, and a period that allows them to recover and catch their breath.

The concept probably won't surprise people who've trained for marathons, triathalons, or bicycle centuries in the past. Athletes have long used interval training to improve their performance and better their finishing times.

But it seems that everyone -- even walkers [1] -- can benefit from intervals because they condition our bodies to burn a lot more fat. Research [2] shows that interval workouts caused people to burn 34 percent more fat than they did with regular workouts. After interval training, our bodies continue to burn more fat than they did before. Intervals also "dramatically improve" cardiovascular fitness, according to the New York [3]Times [4].

The best part? Expect to see results within a few weeks.

Scientists think that intervals work because high-intensity exercise fires up dormant muscle fibers. The lulls enable us to sustain the workout for at least 20 minutes. We can catch our breath and get ready for the next round. The peaks-and-valleys approach gets the heart pumping, while preventing us from burning out within five minutes. About.com has helpful tips [5] and cardio-intensity training program [6] to get started.

Personally, I was never great at tracking my heart rate by counting the beats in my pulse (gasping for air makes that difficult.) So I splurged on a heart rate monitor a few years ago and overall, it's definitely helped me pace myself on bike rides and at the gym. I'll wear it on a ride this weekend for my first official interval workout.

A friend, however, swears by intervals without the aid of a heart rate monitor. Last spring, he trained for a marathon by settling into an easy pace that he could maintain for hours. Then every few minutes, he'd ramp his speed way up, knowing that he only had to sustain it for a minute.

I suppose if intervals helped him run for 26 miles, I can do one or two when I walk [6] my pup around the block.