Association between muscle hydration measures acquired using bioelectrical impedance spectroscopy and magnetic resonance imaging in healthy and hemodialysis population

Establishing the effect of fluctuating extracellular fluid ( ECF ) volume on muscle strength in people with end‐stage renal disease ( ESRD ) on hemodialysis ( HD ) is essential, as inadequate hydration of the skeletal muscles impacts its strength and endurance. Bioelectrical impedance spectroscopy ( BIS ) has been a widely used method for estimating ECF volume of a limb or calf segment. Magnetic resonance imaging ( MRI )‐acquired transverse relaxation times ( T 2 ) has also been used for estimating ECF volumes of individual skeletal muscles. The purpose of this study was to determine the association between T 2 (gold standard) of tibialis anterior ( TA ), medial ( MG ), and lateral gastrocnemius ( LG ), and soleus muscles and calf BIS ECF , in healthy and in people with ESRD / HD . Calf BIS and MRI measures were collected on two occasions before and after HD session in people with ESRD / HD and on a single occasion for the healthy participants. Linear regression analysis was used to establish the association between these measures. Thirty‐two healthy and 22 participants on HD were recruited. The association between T 2 of TA , LG , MG , and soleus muscles and ratio of calf BIS ‐acquired ECF and intracellular fluids ( ICF ) were: TA : β  = 0.30, P  > 0.05; LG : β  = 0.37, P  = 0.035; MG : β  = 0.43, P  = 0.014; soleus: β  = 0.60, P  < 0.001. For the HD group, calf ECF was significantly associated with T 2 of TA ( β  = 0.44, P  = 0.042), and medial gastrocnemius ( β  = 0.47, P  = 0.027) following HD only. Hence BIS ‐acquired measures cannot be used to measure ECF volumes of a single muscle in the ESRD / HD population; however, BIS could be utilized to estimate ratio of ECF : ICF in healthy population for the LG , MG , and soleus muscles.