▁of ▁the ▁body ▁as ▁well ▁like ▁weight , ▁memory , ▁daily ▁function , ▁and ▁many ▁more ▁processes ▁that ▁are ▁necessary ▁for ▁the ▁body ▁to ▁work . ▁Since ▁physical ▁activity ▁impact s ▁all ▁of ▁these ▁important ▁parts ▁of ▁the ▁brain , ▁this ▁form ▁of ▁exercise ▁keeps ▁the ▁neural ▁networks ▁function ing ▁well . ▁Ne ural ▁networks ▁allow ▁information ▁to ▁process ▁and ▁pass ▁to ▁the ▁hi pp oc amp us ▁in ▁order ▁to ▁retain ▁memory . ▁This ▁lets ▁the ▁brain ▁be ▁more ▁efficient ▁in ▁processing ▁and ▁more ▁mem ories ▁are ▁stored ▁this ▁way . ▁ ▁Tra uma ▁and ▁brain ▁expos ure ▁ ▁There ▁is ▁bare ly ▁any ▁re called ▁memory ▁in ▁cases ▁of ▁fear ▁and ▁tra uma ▁expos ure , ▁brain ▁injury , ▁post - tra um atic ▁stress ▁dis order , ▁pain , ▁or ▁anx iety . ▁Rec all ▁memory ▁is ▁very ▁limited , ▁since ▁the ▁only ▁memory ▁people ▁have ▁that ▁suffer ▁from ▁these ▁problems ▁is ▁the ▁flash ▁back s ▁of ▁what ▁happened ▁when ▁the ▁event ▁took ▁place . ▁People ▁can ▁only ▁recall ▁the ▁memory ▁that ▁happened ▁on ▁that ▁day ▁when ▁they ▁hear ▁or ▁see ▁something ▁that ▁brings ▁the ▁memory ▁into ▁existence . ▁They ▁cannot ▁recall ▁how ▁they ▁felt ▁or ▁what ▁they ▁saw , ▁but ▁through ▁images ▁or ▁audio ▁people ▁can ▁recall ▁that ▁trag ic ▁event . ▁For ▁example , ▁the ▁day ▁of ▁September ▁ 1 1 , ▁ 2 0 0 1 , ▁first ▁respond ers ▁remember ▁the ▁day ▁and ▁what ▁it ▁was ▁like ; ▁but ▁the ▁feelings ▁they ▁could ▁not ▁recall .