Resistance training burns calories for more than an hour after a workout and may be as important as aerobic exercise for women in the fight against fat, according to researchers at Johns Hopkins and Arizona State universities.

After women did a series of resistance exercises involving weights, their bodies' energy expenditure was raised for up to two hours after the workout, the study found. Typically, exercises such as jogging or aerobics burn more calories during the workout, but increase metabolism for less than an hour afterward.

"Women who want to lose weight typically do aerobic exercises to raise their heart rate, thinking that's how they can burn the most calories," said Carol A. Binzen, lead author of the study and clinical exercise physiologist at Johns Hopkins. "To get the maximum benefit, women need a combination of cardiovascular workouts and resistance training."

Resistance training is especially important for women older than 25, who potentially can lose up to a half-pound of muscle mass every year, said Binzen.

"Resistance training could have a more lasting effect on metabolism than aerobic exercise. It burns fat and increases muscle mass," she said.

Researchers followed a dozen women ages 24 to 34 who regularly did weightlifting exercises. For the study, on one day the women performed three sets each of 10 repetitions of the following exercises: chest press, shoulder press, leg extension, leg press, seated row, latisimus dorsi pull-down, biceps curl, triceps extension and abdominal crunches. On another day, they sat still and watched a movie.

Binzen and colleagues compared the women's energy expenditures up to two hours after the exercises and while they watched the movie. On average, the resistance exercises burned 155 calories, compared with about 50 calories burned while watching the movie.

"It might not seem like the exercises burned many more calories, but up to two hours after their workout, the women continued to have elevated metabolism as compared to when they watched the movie," Binzen said.

"We studied regular women, not super fitness enthusiasts," she added, "so these results may apply to most moderately active women. Sedentary people would see even a greater benefit at first, but they should always check with their physician before starting an exercise program."

Study results appeared in the June 2001 issue of "Medicine, Science Sports and Exercise," a journal of the American College of Sports Medicine.