Burn Fat 3 Times Faster This Way

As a man, you can accomplish many things in just an hour a week, based on my observations as a graduate student in exercise physiology at the University of Oklahoma. Here's what would not impress me: You watching any reality show with a number in its title. You doing chest bumps with your buddies during a pickup basketball game. You achieving your best score—ever!—on Guitar Hero.

What would impress me is you doing high-intensity intervals as your cardiovascular training. That means alternating between intense bursts of activity and fixed periods of less-intense activity or even complete rest. In fact, you can achieve more progress in a mere 15 minutes of interval training (done three times a week) than that guy grinding away on the treadmill for an hour. An intelligent man draws maximum benefit from a minimum time investment, and smarts are sexy. So are abs, a benefit of this training style. Researchers at Australia's University of New South Wales found that intervals burn three times as much fat as running twice as long at a moderately hard, steady pace.

But interval training's benefits don't end with heart health, fat incineration, or the preservation of that most precious of commodities, your time. Most sports worth playing involve stopping and starting, not running at one pace, so you'll rule on the court or field. What's more, your muscles will learn to contract more forcefully. Ultimately you'll live longer, too, because intervals elevate the good cholesterol that makes your arteries whooshing streams and not plaque-strewn rapids.

How can stopping and starting during cardio do all that? Pretend you're back (or still) in college, and I'm your hot new teaching assistant. Class is now in session, so pop the lid off your latte and listen up.

Lesson 1: When your muscles contract repeatedly during intense training, they quickly use all available energy. So your body searches for fat. While that's going on, your body is quickly losing its ability to flush metabolic by-products from muscle. Ever heard of the burn? That's a buildup of ammonia and other bad stuff. Along with burning, this waste interferes with your body's ability to contract muscles forcefully. If you don't learn to manage the burn properly, your workout is doomed.

Lesson 2: When repeated bouts of high-intensity intervals are separated by short rest periods, each bout begins with a lack of available energy, and muscles that are already fatigued. "Interval training stresses energy systems in the body that aren't accustomed to being used," says Jeramie Hinojosa, M.S., director of the East Texas Medical Center Olympic Center, in Tyler, Texas. "Blood supply to cells increases, the cells use oxygen more efficiently, and the enzymes that help create energy also increase. This improves fitness." What's more, recovery from interval training forces the body to continue burning fat for energy. This all leads to an increase in postworkout calorie burning.

Lesson 3: There are lots of ways to do intervals. Over time you can adjust your ratio between rest and work, change the intensity of your work segment, or alter the length of the entire session. The new interval program that my university colleagues and I have developed produces truly amazing results, and it's perfect for people who don't like endurance training. As part of an experiment to test the ability of a dietary supplement to flush metabolic waste products from muscle tissue, we put a group of active college students (36 men and 33 women) through 6 weeks of high-intensity interval training on the stationary bike. Instead of the usual 30-seconds-on, 30-seconds-off approach, we had the students pedal intensively for 2 minutes, rest completely for 1 minute, and then repeat that sequence four more times. That's only 10 minutes of training! Even with the warmup and rest periods, they were looking at a 20-minute time investment.

After 3 weeks and a total of nine workout sessions, all 69 participants saw huge improvements. The maximum amount of oxygen they could consume—a measure of cardiovascular fitness—increased 11 percent. What's more, they were able to pedal 12 percent longer and complete 44 percent more work. After 6 weeks, the improvements were even more dramatic—18 percent in fitness, 17 percent in time to exhaustion, and nearly 100 percent in work completed.

To achieve the same results, use this workout chart. Measuring your effort accurately and training accordingly is a key to success. Let's assume you can't roll a metabolic cart up to the exercise bike like a scientist would. Your best bet, then, is to measure your heart rate using a monitor so that you can train at a certain percentage of your estimated maximum heart rate (MHR). (You can either use your own portable version, which attaches to your body, or grasp the handles on the machine. Most will provide a readout.)

Your MHR is 220 minus your age. If you're 28, the magic number is 192 beats per minute (bpm). So the goal for your first session would be elevating your heart rate to about 173 bpm (0.90 × 192) for all work intervals. If you look at your monitor and you're not there yet, push those pedals until you are. After 2 minutes, exercise lightly or rest.

Perhaps you're wondering: Is training at more than 100 percent of my maximum heart rate, like the workout chart suggests, even safe? Yes, because your body will make improvements as soon as you start training intensively. What seemed like 100 percent one week will be a level you can surpass the next.

If you don't own a heart-rate monitor or find one hard to use while you're shifting gears as intervals require, do it the old-fashioned way. Immediately after each interval, place your index and middle fingers on your neck just to the side of your Adam's apple or on the thumb side of your wrist. Once you feel a pulse, count the beats for 15 seconds. Multiply by 4 to determine your heart rate.

Bear in mind that even the lowest training level here (90) is quite intense. By the time you reach 100 or higher, you should be pedaling for your life, basically. You can also switch from the stationary bike to any other apparatus that elevates heart rate, including the treadmill, the elliptical trainer, or a jump rope.

As an avid runner and former college athlete, I wish I had known about high-intensity interval training earlier in my career. Huge gains doing cardio only 15 minutes a day three times a week!