Today's gymgoers sing on stationary bikes during Cycle Karaoke, shake their butts at Yoga Booty Ballet, sweat through a high-energy yoga flow class and learn the dance moves to Legally Blonde. They're moving in different ways but they're all trying to get their heart rates up in an interesting, engaging way.
They're doing aerobics.
More than 40 years after Dr. Kenneth Cooper released the book Aerobics, the form of exercise has morphed with the times. Cooper, then a young Air Force physician, invented the word "aerobics," tacking an "s" onto the medical adjective "aerobic" as a way to describe the kind of exercise he was touting. In the 1968 book, he defined aerobic exercises as those that "demand oxygen without producing an intolerable oxygen debt, so that they can be sustained for a long period of time."
But he didn't particularly like the word, and he didn't want it to be the title of his book. "The publisher thought we should call the book Aerobics. I disagreed," he said recently from his office at the Cooper Institute in Texas where, at 77, he still sees patients, including former President George W. Bush. " 'People can't pronounce it, they can't spell it, they won't remember it,' " he recalled contending. "But look what has happened in the past 40 years."
Americans now know — whether they choose to use such knowledge — that getting the heart working for sustained periods of time is beneficial. In the 2008 Physical Activity Guidelines for Americans, the national Centers for Disease Control and Prevention recommends at least 150 minutes of moderate-intensity aerobic activity per week for most adults.
The percentage of Americans working out aerobically increased steadily from 24 percent in 1968 (when Cooper's book came out) to 59 percent in 1984, according to Gallup Polls. (It since has shrunk: A 2006 survey by the National Center for Health Statistics found that 31 percent of Americans exercise aerobically.)
Cooper wrote his book after spending a decade working with the Air Force, studying the effects of exercise and designing a fitness program for pilots and astronauts.
Before Cooper's book, aerobic exercise was the domain of professional athletes; average people were rarely encouraged to get their heart rates up.
"I remember times when the only people we ever studied were athletes because the only people exercising were athletes," said Walter Thompson, a professor in the department of kinesiology and health at Georgia State University.
For women, sweating was considered unladylike; for men over 40, it was considered dangerous.
"My colleagues back in the '50s and '60s were very much afraid of exercise in people over 40 years of age," Cooper said. "I would see titles in newspapers that would say, 'The streets are going to be full of dead joggers' if more Americans follow Cooper.' "
Of course, the opposite happened. "Ken Cooper was, if not the pioneer, one of the pioneers of therapeutic exercise," Thompson said.
The innovation that defined aerobics' appeal — setting heart-pounding movements to music — came from Jacki Sorenson, a former cheerleader at the University of California, Los Angeles.
In 1969, she took the 12-minute fitness test described in Aerobics and scored well, even though "all" she did was dance. She contacted Cooper and showed him a 20-minute dance routine that got the heart racing and would be more attractive to women.
"I still remember that," Cooper said. "I said, 'Jacki, that's great. Go for it!' "
Aerobic dance was born. By the time Jane Fonda released her first aerobic workout videotape in 1982, the country had caught aerobics fever.
These days a panoply of aerobic workouts is available to the fitness-minded, from masters swim clubs, to Tae-Bo, to boot camps, to aerobics dance classes billed as "retro."
"Work up a sweat with a touch of nostalgia in this heart-pumping, traditional aerobics class," reads the description of a "Retro-Robics" class on one health club's Web site. "This time around, legwarmers are optional!"