Sorensen accompanied her husband to his next assignment at Ramey Air Force Base in Puerto Rico in 1969. She found that someone there was already teaching dance classes to Air Force wives, so she determined to start a new exercise program for officers' wives. She studied recent exercise publications including Kenneth H. Cooper's 1968 book Aerobics, which recommended jogging for a healthy heart. Sorensen took his Cooper test and scored "excellent" even though she had never jogged; she realized that her dancing was an equivalent exercise to jogging. She wrote to Cooper and he encouraged her, saying her idea of a dance-based exercise was better, since jogging by itself was not interesting enough for most women to maintain a steady regimen. He recommended that she administer his test to her students, to see how far they could run in 12 minutes. She later said that Cooper's book "changed my life... Dr. Cooper was saying that Americans don’t know what fitness is really all about. They’re worrying about the little muscles in their inner thighs, when they should be worrying about the most important muscle – their hearts."
