Crank Up Your Cardio
When Cardio Was King
When trainer Jim Karas's book The Cardio-Free Diet was published in 2007, he was excited to give readers a new way of thinking about exercise. Based on his 20-plus years in the fitness business, he had come up with a workout strategy that would free people from hours spent jogging or striding away on the elliptical. Karas believed that all that cardio, while improving health, wasn't delivering weight loss. Worse, he felt it was leading to injury, boredom, and even overeating. But then came the backlash -- from the media, exercise experts and the public. "I got blasted," he recalls. "People are addicted to cardio. They think more of it is better, and that's just not true."
Karas, whose latest book is The Ultimate Diet Revolution, may be getting the last laugh. His cardio-free plan involves doing strength work with weights and high-intensity interval training, commonly known as HIIT, in which you alternate challenging bouts with easier recovery periods. The acronym has rapidly become the fitness buzzword. For the last several years, there has been a frenzy of research on high-intensity workouts, even supershort ones (four minutes, anyone?). The aggregate effect of these studies is doing to steady-state cardio what the advent of the Atkins and Zone diets in the 1990s did to carbs: giving it a bad rap. Is cardio -- in the form that we've known and loved -- dead? Is cardio keeping us fat?
It may be hard to believe in this era of all-out war with the expanding American waistline, but regular workouts haven't always been must-dos. The fitness movement didn't really pick up steam until the late 1970s, early 1980s thanks in part to the man who coined the term aerobics, Kenneth Cooper, MD, the founder and chairman of Cooper Aerobics and the Cooper Institute in Dallas. Through his (and his colleagues') extensive research, he made physicians, health experts and the public realize that exercise is good for you, whether you're recovering from a heart attack or trying to lose weight. He and his team have tracked more than 110,000 patients for up to 40 years and published 600 papers on the health benefits of moderate-intensity aerobic exercise. "It's a gold mine of data, all based on good, solid scientific fact," Dr. Cooper says. "Aerobics is not dead; it's more alive than ever. These other things [like HIIT] are just fads."
Researchers typically compare HIIT routines with longer, steady moderate-intensity exercise (what I'll refer to as cardio throughout this article) because there are thousands of studies about the benefits of cardio, as opposed to mere hundreds for HIIT. And the cardio studies are large. For example, a landmark 1989 study of more than 13,000 men and women, which was published in the Journal of the American Medical Association, found that higher fitness levels resulted in a lower risk of death from cardiovascular disease and cancer. It suggested that even moderate exercise -- walking (at about three miles per hour) for 30 to 60 minutes a day -- can reduce mortality risk by almost 50 percent. HIIT studies, on the other hand, tend to be smaller and shorter. After all, it's hard to find people willing to gut it out on a treadmill or stationary bike -- while breathing through a tube and being poked with a needle -- for more than a few weeks.
So if moderate exercise is the holy grail of longevity and disease prevention, then why are so many people bolting from the bandwagon? As Karas explained, people get bored or injured or don't see the weight loss they were hoping for, and exercise, like any healthy habit, can be hard to stick with. But the real problem is time. Once everybody started getting the picture that cardio was really good for you, experts began developing guidelines for how much is needed to deliver benefits. The Centers for Disease Control and Prevention and the American College of Sports Medicine initially recommended a minimum of 30 minutes a day. The Institutes of Medicine advocated at least 60 minutes daily. The current benchmark for health benefits is a minimum of 150 minutes of moderate-intensity aerobic activity every week -- even more if you're trying to lose weight.
"These public health guidelines are based on very good science," says Martin Gibala, PhD, the chairman of the Department of Kinesiology at McMaster University in Hamilton, Ontario, who has been studying HIIT for the past 10 years. "But lack of time is the number-one cited barrier to exercise. People want alternatives that are shorter but just as effective." Gibala's 2008 study of exercisers illustrated how HIIT can save time. He found that 20 to 30 minutes of HIIT three times a week, with a weekly total of only six to nine minutes of "work" (the all-out bursts in between the recovery breaks), boosted fitness levels comparably to exercising at a moderate pace continually for 40 to 60 minutes five days a week (with 200 to 300 total minutes of work time). The government must have heard the rumblings, because in 2008 the Department of Health and Human Services decided that 75 minutes of vigorous-intensity exercise is comparable to 150 minutes of moderate aerobic exercise. By that time, HIIT was hitting its stride.
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