Serena Williams is on course to break the all-time grand slam record.br According to Billie Jean King, fitness could be the key to Serena Williams achieving that goal.br Williams has won a record 23 grand slam singles titles in tennis' Open era.br CNN reports that she could equal Margaret Court's all-time mark with an eighth Wimbledon title.br Williams has struggled with injury this season.br "I would say to everybody: 'You guys ... have to get totally fit.