2.3. Bioelectrical Impedance Spectroscopy (BIS)
Fluid measurements of TBW, ECF, and ICF were obtained at each of the five visits using a multi-frequency BIS device (SFB7 ImpediMed, Queensland, Australia [10–500 kHz]). Subjects were asked to lay supine on the exam table with electrodes placed 5 cm apart at the right wrist and ankle, respectively. Height, weight, age, and sex were entered into the device prior to testing, during which the subject laid supine for 3–5 min prior to measurement to allow for the regulation of posture-related changes in fluid distribution. Device software reported TBW (L), ECF (L), and ICF (L), and an average of two trials was recorded. Reliability in our laboratory for these BIS outcomes within the current sample include: TBW: standard error of measure (SEM) = 0.708 L; ECF: SEM = 0.342 L; ICF: SEM = 0.454 L.