Erin Baiano for The New York Times
TRACY ANDERSON, the tiny blond fitness guru perhaps best known as Gwyneth Paltrow’s trainer and business partner, is as bright and sparkly as the Swarovski crystal-encrusted iPhone case she was admiring one recent Thursday.
“I love this!” she squealed, bouncing on the sofa of the Greenwich Hotel. Then she turned the case over and spied a fighting word: Soul, short for SoulCycle, a popular chain of cycling studios in New York and Los Angeles.
She looked as if she had swallowed something sour, and nearly dropped the bejeweled case. Her girlishness disappeared, and she said flatly: “I can get you better legs than them.”
Ms. Anderson, 37, claims that SoulCycle, through a former employee of hers, uses one of her inventions: a system of resistance bands that hangs from the ceiling. (A SoulCycle spokeswoman had no comment.)
The cycling studios are just one target of the combative Ms. Anderson. At least half a dozen of her former employees have released exercise DVDs or have opened their own studios — their clients include Madonna, Anne Hathaway and Kelly Ripa — many peddling workouts she said were derived in “an opportunistic way” from the intense, heart-in-throat dance routines and minimal-weight, high-repetition “muscular structure” moves Ms. Anderson has spent 14 years perfecting.
Her influence can be found in almost any gym featuring the type of jump-heavy cardio dance classes she has popularized or a version of what Ms. Anderson calls her “weird free arms” — essentially waving the arms from every conceivable angle for minutes at a time.
“It makes me sad for humanity, actually, that people would take all my hard work and then pose like they have a method that they have tried and tested,” she said of her former employees, becoming so angry she struggled for words. “They’re not even lip-syncing what I do. They’re, like, karaokeing off my songs.”
She added: “But the nice thing about it is that as a company, Gwyneth and I have been really smart like Coca-Cola and we didn’t teach any of those trainers how or why I move the way I do.”
Ms. Anderson, who was born in Indiana, studied musical theater for two years at the American Musical and Dramatic Academy in New York. She insisted she did not owe anything to Jane Fonda, the original dance aerobics queen, because Ms. Fonda was “a motivator, but she never claimed to have a method.”
Ms. Anderson described her own philosophy as “the method,” and talked passionately about the science behind it, tossing around terms like “proprioception perception,” “strength of synapses” and “muscle confusion.”
“I move across the large muscles in a way like when you were a kid you got an Indian burn, building collective strength between muscle groups,” she explained with a smile.
Ms. Anderson has not sought certification in fields like exercise physiology or teaching, she said, because, “I am so hard on myself with not deviating the amount of time that I have for research and development of the method.”
As for coming up with moves to slim problem areas where women are predisposed to store fat (“disproportionate struggle,” in Ms. Andersonspeak), she painted a vivid picture.
“I’m completely focused on how can I get forces to travel from opposing directions and end up creating a contraction in a muscle that’s going to then pull in,” she said. “And then as we lose the fat the muscular structure will be vibrating so well that it will have the connective tissues pull the skin back to it.”
Richard Cotton, an exercise physiologist and the national director of training for the American College of Sports Medicine in Indianapolis, said there is “a ton of research that disputes the idea of spot-reduction.”
“You can’t choose where the body loses fat,” he said.
Gary Diffee, a professor of kinesiology at the University of Wisconsin-Madison who examined some of her claims, said, “Like many things of this type, the science seems to be a mixture of true, kind of true, true but irrelevant to the point she is trying to make, and wrong.”
“The main thing is that she is getting people to move,” Dr. Diffee said.