A Two-Stage Regression Using Bioimpedance and Temperature for Hydration Assessment During Sports

Bio impedance analysis (BIA) estimates the amount of total body water (TBW) in the human body. During sports, however, the increased skin temperature distorts bio impedance measurements and, thus, prevents the application of BIA. In this paper, we propose a two-stage regression that includes temperature information in order to correct the temperature-distorted bio impedance. In detail, the first regression stage corrects temperature-distored bio impedance using information of skin and core temperature. The second regression stage estimates TBW loss on basis of the corrected bio impedance. The two-stage regression was evaluated using data of an ongoing study. The results showed that estimations of TBW loss during sports can be considerably improved if temperature information is included. However, a remaining error was still observed. Therefore, additional measurements, e.g., skin blood flow, are discussed because they also influence bio impedance and could further reduce the error.