Where health and energy conservation meet: Hong Kong’s California Fitness.

A health club here is hoping that a car battery, some StairMasters and dozens of gym rats can help ease the world’s energy problems.

Rita Wong is doing her part. One evening recently, the fit 27-year-old, dressed in black spandex, pedaled furiously on an elliptical machine at the California Fitness health club. As she worked up a sweat to a Madonna song blasting on the gym’s sound system, the energy she created was transformed into electricity and stored in a battery that powers some of the gym’s lights.