(a) A subject configured with both the wearable patch and the COSMED K5 system, with inset showing a zoomed-in image of the ECG electrodes. (b) The wearable patch top, bottom, and inside. The microSD (1), microUSB (2), and battery (3) are shown. (c) A map of the outdoor walking route across Georgia Institute of Technology with marked terrain. (d) An outline of the study protocol.