She was the first woman to officially win the Boston Marathon, 1972. Alongside Beth Bonner, Kuscsik became the second American woman to complete a marathon in under three hours, running a time of 2:56:04 at the 1971 New York City Marathon (Bonner did so in the same race with 2:55:22).
In addition to her running feats, she was New York State women's speed skating champion, New York State women's roller-skating champion, and New York State women's bicycling champion, all in same year. She was instrumental in influencing the U.S. Amateur Athletic Association, in late 1971, to increase its maximum distance for sanctioned women's races, leading to official participation by women in marathons, beginning at Boston in 1972.