Sedentary Sphere
The Sedentary Sphere is a method for visualising the output of a wrist-worn triaxial accelerometer. It aids the development of algorithms for the analysis and identification of sedentary behaviours.
It is well known that the output of an accelerometer within a moving wearable can be used to approximate energy expenditures, steps taken and activity type. However, when stationary the predominant signal is from the Earth’s gravitational field and this can be used to determine the wearer’s posture.
The Sedentary Sphere describes all the possible outputs of a static, wrist-worn, tri-axial accelerometer commonly described in terms of wrist rotation and arm elevation. The further the signal moves away from the sphere’s surface the more energy is present in the motion.