Purpose: The exercise-induced increase in skin and body temperature, cutaneous blood flow and electrolyte accumulation on the skin affects the validity of bioimpedance analysis (BIA) to assess post-exercise changes in hydration. This study aimed to assess the influence of a 10-min cold (22°C) shower on the time course of impedance measurements after controlled exercise.
Methods: Ten male athletes (26.2±4.1 yr and BMI 23.9±1.7 kg/m2) were tested on two different days. During both trials, athletes ran for 30 min on a treadmill in a room at 22°C. In a randomized cross-over trial, the participants underwent a 10-min cold shower in the trial occasion and did not shower in the control trial. BIA variables were measured before running (i.e. baseline (T0)), immediately after exercising (T1), then at 20 (T2), 40 (T3) and 60 min (T4) after the exercise. The shower was performed after T1 in the shower trial.
Results: Body weight decreased similarly after running (-0.4±0.1%, p<0.001 and -0.4±0.1%, p<0.001). Resistance and vector length returned to baseline at T2 in the shower trial, whereas baseline values were achieved at T3 in the control trial (p>0.05). In the control trial, reactance remained at a lower level for the entire testing period (38.1±6.9 vs. 37.3±6.7, p<0.001). Forehead skin temperature returned to baseline values at T2 with shower, while it was still high at T4 without shower (p<0.001).
Conclusions: The present data show that a 10-min cold shower enables the stabilization of BIA measurements within 20 min after exercise, which might facilitate the assessment of hydration change after exercise.
Keywords: BIVA; dehydration; phase angle; reactance; resistance.