Monitoring of Posture Allocations and Activities by a Shoe-Based Wearable Sensor

TLDR

Monitoring posture and activity helps estimate energy expenditure and support obesity prevention, but current accurate devices rely on multiple body sensors, making them obtrusive. The study introduces a shoe‑based wearable sensor that accurately recognizes common postures and activities. The sensor captures heel‑acceleration and plantar‑pressure patterns, which uniquely identify postures and activities, and these signals were classified with support‑vector machines in a nine‑person test set. The device achieved 95.2 % overall accuracy and over 98 % on an optimized sensor set, maintained 98 % accuracy even when sampling was reduced to 1 Hz, and performed well across users with diverse shoe sizes and BMI.

Abstract

Monitoring of posture allocations and activities enables accurate estimation of energy expenditure and may aid in obesity prevention and treatment. At present, accurate devices rely on multiple sensors distributed on the body and thus may be too obtrusive for everyday use. This paper presents a novel wearable sensor, which is capable of very accurate recognition of common postures and activities. The patterns of heel acceleration and plantar pressure uniquely characterize postures and typical activities while requiring minimal preprocessing and no feature extraction. The shoe sensor was tested in nine adults performing sitting and standing postures and while walking, running, stair ascent/descent and cycling. Support vector machines (SVMs) were used for classification. A fourfold validation of a six-class subject-independent group model showed 95.2% average accuracy of posture/activity classification on full sensor set and over 98% on optimized sensor set. Using a combination of acceleration/pressure also enabled a pronounced reduction of the sampling frequency (25 to 1 Hz) without significant loss of accuracy (98% versus 93%). Subjects had shoe sizes (US) M9.5-11 and W7-9 and body mass index from 18.1 to 39.4 kg/m2 and thus suggesting that the device can be used by individuals with varying anthropometric characteristics.