fitness vs prime of life

fitness

noun
  • The cultivation of an attractive and/or healthy physique. 

  • The condition of being attractive, fanciable or beautiful. 

  • The condition of being fit, suitable or appropriate. 

  • An organism's or species' degree of success in finding a mate and producing offspring. 

prime of life

noun
  • The period of one's mature life when one is at a peak of health and performance. 

How often have the words fitness and prime of life occurred in a corpus of books? (source: Google Ngram Viewer )