The volunteer, just before and just after a gun loaded with blanks was fired behind him, illustrates the SFLs involvement in the startle response. The Rectus Abdominus, sterna fascia, and SCM all spastically contract, bringing the pelvis into a posterior tilt, sternum down, flexing the cervicals and hyperextending the head. This armors our front and strengthens our back, while allowing our eyes to remain oriented to the horizon so we can spot any threats. This survival mechanism is cross cultural and exists in most animals as well.