Make Your Cardio Work for You

Better cardio workouts
The sure-fire way to an effective cardio workout? A heart-rate monitor.

One proviso: "Monitors that claim to give caloric expenditure are at best questionable," warns Kosich. "They base the calories-expended figure on body weight and heart rate without including the workload factor, such as speed or grade, so the number is likely to be off by a lot of calories."

If you don't have a heart-rate monitor, you can measure your maximum heart rate (MHR) yourself. To measure your MHR as called for throughout this workout, subtract your age from 220. Then, multiply that number by the percentage for your interval level. For example, if you're 30 years old and a beginner doing the Days 1 and 3 workout, multiply 190 by 60 percent, which gives you an MHR of 114 (eg. 190 X .60=114). This means you need to keep your heart rate at 114 beats per minute for 30 minutes.

While exercising you can determine your heart rate by taking your pulse and counting the beats for 10 seconds. Then, multiply by 6 to get your 1-minute heart rate. For example, if you get a 15-beat count at 10 seconds, your MHR is 90, which means you're not working hard enough.