Relationship Between Wearable Sensor Foot Strike Outcomes And Ankle Sagittal Plane Kinematics During Treadmill Running

Abstract

PURPOSE: Wearable sensors are capable of measuring biomechanical running outcomes. Traditional gait analyses have determined a strong relationship between ankle angle at initial contact and foot strike. However, there is currently no information available on how sensor-derived metrics of foot strike type relate to ankle sagittal motion during running as a means of validation. Therefore, the purpose of this study was to validate the sensor-derived foot strike type outcome by determining the relationship between foot strike type and ankle sagittal plane kinematics during a treadmill running analysis. We hypothesized that a rearfoot strike (RFS) would highly correlate to increased ankle dorsiflexion, while a forefoot strike (FFS) would highly correlate to increased ankle plantarflexion. METHODS: Twenty collegiate cross-country athletes (12 females) ran on an instrumented treadmill with 3-D motion capture at standard (2.68 m/s) and fast (3.60 m/s) speeds. Foot strike outcomes were obtained bilaterally using running wearable sensors, and sagittal plane ankle kinematics were simultaneously recorded. Pearson’s r correlation coefficients were used to determine the relationship between sensor-derived foot strike categories (1 to 16), and ankle angles at initial contact. Dorsiflexion was defined as in the positive axis. Alpha was set a priori to .05 for all analyses. RESULTS: Eight hundred total steps were included for analysis. Foot strike type and ankle angles at initial contact had a strong, inverse correlation, such that a higher foot strike value was strongly related to increased ankle plantarflexion angles (r = -0.85, p<.001, Figure). CONCLUSIONS: Sensor-derived foot strike metrics were highly correlated to sagittal plane ankle measures, thus confirming our initial hypotheses. These outcomes support that the running wearable sensors are a valid means to assess foot strike patterns during distance running.