Under ▁F SB PT ▁in ▁the ▁United ▁States ▁of ▁America ) ▁Ass ist ants ▁( Phys ical ▁Ther apy ▁Ass istant ▁or ▁P TA ) ▁may ▁use ▁these ▁tools . ▁There ▁are ▁some ▁modal ities ▁that ▁can ▁be ▁used ▁by ▁the ▁patient / client ▁on ▁themselves ▁with ▁instruction ▁and ▁training ▁such ▁as ▁super f icial ▁he ating ▁agents ▁or ▁hot ▁pack s . ▁However ▁the ▁Mod al ities ▁or ▁Phys ical ▁Ag ents ▁often ▁have ▁a ▁certain ▁setting ▁or ▁pres cribed ▁conditions ▁such ▁as ▁specific ▁temperature , ▁material ▁used , ▁duration ▁of ▁application ▁and ▁position ing ▁that ▁make ▁affect ▁the ▁effic acy ▁or ▁even ▁safety ▁of ▁home ▁use , ▁thus ▁the ▁need ▁for ▁instruction ▁prior ▁to ▁use . ▁ ▁Cont ra ind ic ations ▁Each ▁Phys ical ▁Agent ▁or ▁Mod ality ▁has ▁a ▁different ▁contra ind ic ation ▁based ▁on ▁how ▁the ▁tool ▁affect s ▁the ▁normal ▁phys i olog ic ▁function ▁of ▁the ▁body ▁and ▁how ▁the ▁tool ▁affect s ▁the ▁type ▁of ▁condition ▁possessed ▁by ▁the ▁site ▁to ▁be ▁treated ▁on ▁the ▁patient / client ▁of ▁the ▁P T . ▁Im pro per ▁and ▁un in formed ▁use ▁of ▁these ▁modal ities ▁can ▁sometimes ▁cause ▁severe ▁irre vers ible ▁damage . ▁EX : ▁ul tras ound / elect ro ther apy ▁on ▁the ▁ab d omen ▁of ▁a ▁pre gn ant ▁patient ▁can ▁harm ▁the ▁baby . ▁Ex cess ive ▁heat ▁with ▁use ▁of ▁hot ▁pack s ▁may ▁cause ▁first ▁to ▁second ▁degree ▁burn s . ▁ ▁C ategories ▁Th erm