▁Le an ▁Mass , ▁if ▁strict ▁gu idel ines ▁are ▁ad her ed ▁to . ▁ ▁Historical ▁background ▁ ▁Elect rical ▁properties ▁of ▁t issues ▁have ▁been ▁described ▁since ▁ 1 8 7 2 . ▁These ▁properties ▁were ▁further ▁described ▁for ▁a ▁wider ▁range ▁of ▁frequencies ▁on ▁a ▁larger ▁range ▁of ▁t issues , ▁including ▁those ▁that ▁were ▁dam aged ▁or ▁under going ▁change ▁after ▁death . ▁ ▁In ▁ 1 9 6 2 , ▁Thom asset ▁conducted ▁the ▁original ▁studies ▁using ▁elect rical ▁imped ance ▁measurements ▁as ▁an ▁index ▁of ▁total ▁body ▁water ▁( TB W ), ▁using ▁two ▁sub cut ane ously ▁inserted ▁need les . ▁ ▁In ▁ 1 9 6 9 , ▁Hof fer ▁concluded ▁that ▁a ▁whole ▁body ▁imped ance ▁measurements ▁could ▁predict ▁total ▁body ▁water . ▁the ▁equation ▁( the ▁squ ared ▁value ▁of ▁height ▁divided ▁by ▁imped ance ▁measurements ▁of ▁the ▁right ▁half ▁of ▁the ▁body ) ▁showed ▁a ▁correlation ▁coefficient ▁of ▁ 0 . 9 2 ▁with ▁total ▁body ▁water . ▁This ▁equation ▁Hof fer ▁proved ▁is ▁known ▁as ▁the ▁imped ance ▁index ▁used ▁in ▁B IA . ▁ ▁In ▁ 1 9 8 3 , ▁Ny ober ▁valid ated ▁the ▁use ▁of ▁whole ▁body ▁elect rical ▁imped ance ▁to ▁assess ▁body ▁composition . ▁ ▁By ▁the ▁ 1 9 7 0 s ▁the ▁found ations ▁of ▁B IA ▁were ▁established , ▁including ▁those ▁that ▁under p inned ▁the ▁relationships ▁between ▁the ▁imped ance ▁and ▁the ▁body ▁water ▁content ▁of ▁the ▁body . ▁A ▁variety