Ear-worn wearables (aka: earbuds, hearables, or earables) are commonly used by runners for entertainment, and many modern devices also include inertial sensors for user interaction. We propose harnessing the technology embedded in earbuds to capture fundamental aspects of running mechanics and make them available to the wider community of users, outside a lab setting. While other wearables such as insoles, or ankle/sacrum mounted IMUs have already been presented, ear-worn devices may have a better potential for adoption and therefore offer an optimal compromise between validity of running gait analysis and usability. Thirty healthy participants (18 male, 12 female) ran on an instrumented treadmill (54000 gait cycles) and floor-mounted force plates (2800 gait cycles) at a variety of speeds. Building on the information brought about by the vibrations transmitted to, and motion of the head, we devised a gait event detection algorithm and a regression model to predict vertical ground reaction force (vGRF) waveforms. The validation of outcomes against quantities from force plates shows an average MAPE of 4.8 % on temporal metrics and 9.0 % on scalar GRF derived metrics. Additionally, the model tracks the full vGRF curve well, achieving an NRMSE of 11.1 % on unseen participants. Overall, we show comparable accuracy from an ear-worn consumer device in temporal and kinetic gait parameter estimation to specialist devices, paving the way for accessible running gait monitoring.
Stuchbury-Wass et al. (Tue,) studied this question.