Abstract: Vertical center of mass movement measuring apparatus comprising an inertial sensing device, for producing outputs relating to rotation and acceleration in its local frame of reference and configured for fastening to the back of an animal, preferably a person, a memory and a processor, wherein the processor is programmed to provide a quaternion corresponding to the rotation of the inertial sensing device and a first acceleration, both based on an output of the rotation sensing device, and the processor is programmed to combine the quaternion and the first acceleration and based on the result of the combination to provide, when the device is fastened close enough to the center of mass of a moving object such as a person, an estimate of vertical displacement, or a derivative of vertical displacement, of the center of mass in a global reference frame.

Abstract: A system for measuring variation in the gait of a subject comprises a sensor arranged to measure variations in vertical position of the subject while the subject takes a series of steps, a processor, and a display. The processor is arranged to identify a plurality of points in a first one of the steps and a plurality of points in a second one of the steps, to identify a plurality of pairs of the points, each pair comprising one point in each of the steps, to determine a value of height for each of the points in each of the pairs, and to control the display to produce a display plotting the heights of the two points in each pair against each other.

Abstract: Vertical centre of mass movement measuring apparatus comprising an inertial sensing device, for producing outputs relating to rotation and acceleration in its local frame of reference and configured for fastening to the back of an animal, preferably a person, a memory and a processor, wherein the processor is programmed to provide a quaternion corresponding to the rotation of the inertial sensing device and a first acceleration, both based on an output of the rotation sensing device, and the processor is programmed to combine the quaternion and the first acceleration and based on the result of the combination to provide, when the device is fastened close enough to the centre of mass of a moving object such as a person, an estimate of vertical displacement, or a derivative of vertical displacement, of the centre of mass in a global reference frame.