▁et ▁al . ▁remarked ▁in ▁ 2 0 1 3 ▁that ▁signs ▁of ▁the ▁after - effect ▁could ▁be ▁measured ▁before ▁foot - s led ▁contact , ▁suggesting ▁that ▁the ▁after - effect ▁is ▁what ▁they ▁label led ▁a ▁' pre - empt ive ▁post ural ▁response '. ▁ ▁The ▁after - effect ▁is ▁pre - empt ive ▁in ▁that ▁it ▁anticip ates ▁a ▁threat ▁to ▁balance ▁rather ▁than ▁being ▁triggered ▁by ▁one . ▁Post ural ▁control ▁is ▁usually ▁generated ▁by ▁an ▁external ▁threat , ▁for ▁example ▁a ▁sli pp ery ▁surface ▁will ▁lead ▁to ▁a ▁more ▁ca ution ary ▁g ait , ▁but ▁in ▁this ▁case ▁the ▁post ural ▁adaptation ▁is ▁an ▁a vers ive , ▁' just ▁in ▁case ' ▁strategy . ▁When ▁ste pping ▁onto ▁the ▁broken ▁es cal ator , ▁the ▁person ▁will ▁anticip ate ▁its ▁movement , ▁just ▁to ▁make ▁sure ▁they ▁would ▁not ▁fall ▁if ▁the ▁es cal ator ▁were ▁to ▁move . ▁The ▁person ▁undert akes ▁a ▁' wor st ▁case ▁scenario ' ▁which ▁seems ▁the ▁most ▁strateg ic ▁option : ▁prepar ing ▁for ▁the ▁platform ▁to ▁move ▁even ▁though ▁it ▁won ' t ▁is ▁better ▁than ▁the ▁opposite . ▁ ▁Indeed , ▁as ▁well ▁as ▁the ▁distinction ▁between ▁the ▁motor ▁and ▁cogn itive ▁systems , ▁another ▁factor ▁leading ▁to ▁the ▁after - effect ▁has ▁been ▁argued ▁to ▁be ▁fear - related ▁mechan isms . ▁The ▁fear ▁of ▁falling ▁if ▁somehow ▁the ▁es cal ator ▁moved ▁could ▁be ▁enough ▁to ▁adopt ▁a ▁pre ca ution ary