根据材料，完成题。 Fitness Movement The fitness movement that began in the late 1960s and early 1970s centered around aerobic exercise.Millions of individuals became engaged in a variety of aerobic activities, and51thousands of health spas developed around the country to capitalize on his52interest in fitness, particularly aerobic dancing for females. A number of fitness spas existed53to this aerobic fitness movement, even a national chain with spas in mo