Electrodermal Activity and Electrocardiogram during submaximal exercise test

Subjects for whom exercise represents a low risk level, based on standardized guidelines from the American College of Sports Medicine (ACSM) [20], were asked to participate in the study. Eighteen healthy subjects, 11 males and 7 females, age 21 ± 3 years were enrolled. Participants were asked to avoid caffeine and alcohol during the 48 hours preceding the test, and were instructed to fast (water only) for at least 3 h before testing. The study was conducted in a quiet, comfortable room (ambient temperature, 18-20 °C, and relative humidity between 30-50%). All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study. This protocol was approved by the Institutional Review Board of the University of Connecticut.

Before the exercise test began, the subjects were asked to lay in the supine position for 5 min to procure hemodynamic stabilization prior to 5 minutes of data collection in this position. ECG and EDA were measured simultaneously for each subject throughout the entire experiment. The ECG signal was used to monitor subjects’ HR throughout the experiment. An HP ECG monitor (HP 78354A) and GSR ADInstruments module were used. Three hydrogel Ag-AgCl electrodes were used for ECG signal collection. The electrodes were placed on the shoulders and lower left rib. In addition, a pair of stainless steel electrodes were placed on index and middle fingers of the right hand to collect the EDA signal. Subjects were instructed to keep their right hand stable, raised at chest height. The skin was cleaned with alcohol before placing the ECG and EDA electrodes. The leads were taped to the subject’s skin using latex-free tape, to avoid movement of the cables, which can corrupt the signals. All signals were acquired through the ADInstruments analog-to-digital converter, and compatible PowerLab software, while the sampling frequency was fixed to 400 Hz for all signals. Participants were asked to wear their own active wear/gym clothes during the protocol with the shirt covering the electrodes and cables during the experiment.

Subjects were first monitored for 5 min at rest (supine, without any movement or talking) to measure resting HR and EDA. The subjects then performed the incremental test on a motorized treadmill (Life Fitness F3). 85% HRmax was calculated from the equation HRmax = 206.9-(0.67*age).

The incremental running began with an initial warm-up, followed by walking at 3mi/h (~ 4.82 km/h). The speed was increased to 5 mi/h (~ 8 km/h) and increased 0.6 mi/h (about 1 km/h) every subsequent minute until the subjects reached 85% of their HRmax. When a subject reached 85% of HRmax within 2 min of running, the data were excluded because at least 2 minutes of data are required for processing. The 18 subjects enrolled for this study represents those who were able to provide at least 2 minutes of data prior to reaching 85% of HRmax. After subjects reached 85% of their HRmax, treadmill speed was reduced to 5 mi/h (~ 8 km/h) for another 4 min to start the recovery phase, followed by walking at 3 mi/h (about 4.82 km/h) for 5 minutes. A final 10 min period (or more if needed to achieve baseline HR) in the supine position was utilized to allow HR to return to baseline. The duration of the experiment was approximately one hour.