Women-only gyms, once seen as the exercise alternative for out of shape women of a certain age, are actively shedding that reputation, fitness experts say.

As for the workouts, Shear believes that while women are certainly capable of doing everything that men do, many find the gym equipment in weight rooms bulky, off-putting and ill suited to them.

Curves International, Inc., the large chain of fitness centers for women, is known for its 30-minute circuit of cardio, strength and stretching training.

Karass said Curves had initiated a rigorous, high-intensity interval training workout designed by trainer Jillian Michaels, of the TV reality show "The Biggest Loser," to attract younger women.

Karass, 50, believes women's gyms are simply less intimidating than co-ed clubs.

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