Devices, systems, and, methods for measuring deformation variation in an insole to determine characteristics of a user, including weight and gait, are described herein. In some embodiments, a device includes an insole having a fluid reservoir configured to be disposed in a shoe, a deformation sensor, and a communications module. The fluid reservoir includes a first portion and a second portion. The deformation sensor is coupled to the fluid reservoir and is configured to measure a deformation in at least one of the first portion and the second portion. The communications module is configured to receive the measured deformation from the deformation sensor and transmit the measured deformation to a remote device.
