aerobics vs keep fit

aerobics

noun
  • A form of exercise, designed to enhance one's cardiovascular fitness, normally performed to music. 

keep fit

noun
  • exercises designed to promote physical fitness if performed regularly. 

  • Organised group aerobics class 

verb
  • To exercise for physical fitness. 

How often have the words aerobics and keep fit occurred in a corpus of books? (source: Google Ngram Viewer )