break a sweat vs perspire

break a sweat

verb
  • To start sweating. 

  • To put effort into something. 

perspire

verb
  • To emit (sweat or perspiration) through the skin's pores. 

  • To be evacuated or excreted, or to exude, through the pores of the skin. 

How often have the words break a sweat and perspire occurred in a corpus of books? (source: Google Ngram Viewer )