*3.1. Smart Watch*

There has been an increase in the popularity of wrist-worn sensors, such as smart watches and bands, in recent years. The majority of these devices use inertial sensors, such as accelerometers, in conjunction with health monitoring sensors, such as galvanic skin response and heart rate sensors. In this work, we have chosen to use the Microsoft Band 2. This is a "smart band" type of device and is equipped with a wide range of sensors, including three-axis accelerometer, gyrometer, optical heart-rate sensor, Galvanic Skin Response sensor (GSR), ambient light sensor, ultraviolet light exposure sensor and skin temperature sensor. The device offers a choice among three sampling periods for the accelerometer, namely 16, 32 and 128 ms. During our experimental procedure, we selected a sampling period equal to 32 ms, which results in a sampling frequency of 31 Hz approximately. This is appropriate for our application area, since the frequency required to assess daily physical activities is 20 Hz [34].
