days      fitness    w   age                   
   29.0      low        1   18.3
   42.0      low        2   30.0
   38.0      low        3   26.5
   40.0      low        4   28.1
   43.0      low        5   29.7
   40.0      low        6   27.8
   30.0      low        7   19.8
   42.0      low        8   29.3
   30.0      medium     1   20.8
   35.0      medium     2   25.2
   39.0      medium     3   29.2
   28.0      medium     4   20.0
   31.0      medium     5   21.5
   31.0      medium     6   22.1
   29.0      medium     7   19.7
   35.0      medium     8   24.7
   29.0      medium     9   20.2
   33.0      medium    10   22.9
   26.0      high       1   22.7
   32.0      high       2   28.7
   21.0      high       3   18.9
   20.0      high       4   18.0
   23.0      high       5   21.7
   22.0      high       6   20.0