Martina Navratilova is always working.
Martina Navratilova ( Martina Navrátilová [ ˈmarcɪna ˈnavraːcɪlovaː ] ; born Martina Šubertová [ ˈmarcɪna ˈʃubɛrtovaː ] ; October 18 , 1956 ) is a Czech and American retired tennis player and coach . She was year-end singles No. 1 seven times , including a record five consecutive years , as well as year-end doubles No. 1 five times , including three consecutive years during which she held the ranking for the entire year . Over five consecutive seasons , she won 428 of 442 singles matches , averaging fewer than 3 losses per year to 87 wins , for a sustained winning percentage of 96.8 % .