hyperextension

/HH AY0 P ER0 IH0 K S T EH1 N SH AH0 N/
noun
  1. 1

    The extension of a joint beyond its normal range; the condition of being hyperextended.

  2. 2

    An exercise performed by lying on the stomach, ideally inclined upwards as on a Roman chair to reach a higher range of motion, and raising and lowering the upper torso.

Source: https://en.wiktionary.org/wiki/hyperextension