问题：
[单选] 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 most major cities. However, their54was not on aerobics, but rather on weight-training programsdesigned to develop muscular mass, 55, and endurance in their primarily male56. These fitness spas did not seem to benefit57from the aerobic fitness movement to better health, since medical opinion suggested that weight-training programs58few, if any, health benefits. In recent years, however, weight training has again become increasingly. 59for males and for females. Many60programs focus not only on developing muscular strength and endurance but on aerobic fitness as well.61, most physical fitness tests have usually included measures of muscular strength and endurance, not for health related reasons, but
primarily62such fitness components have been related to performance in athletics.63, in recent years,evidence has shown that training programs designed primarily to improve muscular strength and endurance might also offer some health64as well. The American College of Sports Medicine now65that weight training be part of a total fitness program for healthy Americans.
请在第__(51)__处填上正确答案。
A . affluently
B . eligibly
C . gorgeously
D . literally
