High-impact aerobics' stepsister, cardiofunk--which marries dance club moves and hip hop music in a low-impact aerobics format--was born at her gym several years later. A version of this class, which is trademarked by Voight, is still taught at her Santa Monica studio.
Its cousin, city jam, another Voight creation that was designed in conjunction with one of her students, soon followed. It features low-impact moves and contemporary music. The concept was taken up by Reebok, which named a shoe after it.
The latest trend to which Voight has given her unique twist is spinning, which pairs stationary-bike riding and the ear-ringing music that accompanies high-impact aerobics.
To promote her take on the concept, Voight developed two videos, "Power Pacing" and "Pace and Shape," in conjunction with stationary-bicycle maker Keiser Sports Health Equipment of Fresno.
Industry statistics bear out Voight's ability to stay ahead of the pack: The number of people participating in low-impact aerobic classes increased 16% in 1995 and those who turned to stationary biking for a workout jumped 12% in 1995, according to an annual sports participation survey by Hartsdale, N.Y.-based American Sports Data.
The Covina native is looking past those she's converted to the fit way of life and toward the average, time-starved person with a mortgage, kids and a demanding job.
"I want to know how you can stay fit when you have kids and your schedule just doesn't allow it," Voight said. She sees the fitness industry moving toward more convenient methods of staying in shape.
Her instincts are confirmed by industry statistics that show a fitness boom being driven by exercise equipment sales. The number of people exercising at home skyrocketed 101% in 1995, said Harvey Lauer, president of American Sports Data.
Voight wants to sign more endorsement deals with companies that manufacture healthy lifestyle products, ranging from active wear to vitamins to makeup to hair products.
She sees her recent Nordstrom deal, together with an effort by Hyperion to get her books into Disney stores, as an opportunity to move her products into broader markets.
Students who frequent Voight's studio, many of whom have remained loyal to her for years, are not so keen on sharing her with the rest of the world.
"As soon as I took one class from her, I lost all interest in other forms of physical activity," said Steve Ostro, 50, a scientist at the Jet Propulsion Laboratory in Pasadena. "I've been suffering because she only teaches high-impact classes twice a week now."
Voight's die-hard pupils lament the demise of high-impact aerobics and the shift in the industry toward step classes, spinning and other low-impact forms of exercise.
They say it's obvious that although Voight is constantly reinventing her fitness business, her first love is teaching.
"There's no one like Karen. There's no one that moves like that and cares so much about their students," said Rina Mark, a 51-year-old freelance meeting planner who has been working out with Voight for seven years.
"She's the real item."