contortion vs flexion

contortion

noun
  • The act of contorting, twisting or deforming something, especially oneself. 

  • A form of acrobatic display which involves the dramatic bending and flexing of the human body. 

flexion

noun
  • The state of being bent or flexed. 

  • Deviation from straightness. 

  • The act of bending a joint, especially a bone joint; the counteraction of extension. 

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