Electrode placement in bioimpedance spectroscopy

In order to maintain a homeostatic environment in human cells, the balance between absorption and separation of water must be retained. Imbalance will have consequences on both the cellular and organ levels. Studies performed on athletes have shown coherence between their hydration status and ability to perform. A dehydration of 2-7% of total body weight resulted in a marked decrease in performance. Measurement and monitoring of hydration status may be used to optimize athlete performance. Therefore, in this current study bioimpedance spectroscopy is used to determine the hydration status of athletes. Trials were made to investigate alternative ways of electrode placement when performing bioimpedance spectroscopy in order to measure relative dehydration. A total of 14 test subjects underwent measurements before, during, and after a cycle test of 3×25 min. Electrodes where placed to measure body impedance in three different ways: wrist-ankle (recommended method), wrist-wrist, and transthoracic. Furthermore, the relative loss in weight of the subjects during the trial was registered. The study showed no relation between relative weight loss and the wrist-wrist and transthoracic placement method, using bioimpedance spectroscopy to measure relative dehydration. The inability of the method to detect such relative changes in hydration may be due to the bioimpedance spectroscopy technology being extremely sensitive to changes in skin temperature, movement artifacts, thoroughness in placing the electrodes, and the physiological impact on the human body when performing exercise. Therefore, further research into the area of bioimpedance spectroscopy is needed before this methodology can be applied in monitoring active athletes. Hence, a simple weight measurement still seems a more useful way of determining a relative change of hydration in an active setting.