# The Effects of Decreasing Foot Strike Angle on Lower Extremity Shock Attenuation Measured with Wearable Sensors

## TL;DR

This study shows that changing foot strike angle affects how the lower leg absorbs impact during running, as measured by wearable sensors.

## Contribution

The study introduces a novel method to assess lower extremity shock attenuation using wearable sensors during gait modifications.

## Key findings

- Forefoot striking significantly increased resultant shock attenuation at the ankle and below/knee sensor combinations.
- No significant changes were observed in vertical shock attenuation or the ankle/knee sensor combination.
- Shock attenuation may reflect overall lower extremity loading changes but not joint-specific loading.

## Abstract

Shock attenuation may be a clinically feasible method to assess changes in lower extremity joint loading induced by gait modifications, such as decreasing foot strike angle (forefoot striking). The purpose of this study was to identify changes in lower extremity shock attenuation between habitual and forefoot strike gait conditions. Eighteen participants ran on a treadmill with their habitual gait and an instructed forefoot strike gait. Shock attenuation was measured with inertial measurement units as the ratio of proximal to distal peak resultant/vertical accelerations, with three sensor combinations: ankle to below/above knee (BK/A; AK/A) and AK/BK. Three participants were excluded who were habitual forefoot strikers or failed to decrease their foot strike angle by at least 5° in the forefoot strike condition. The results showed significantly greater resultant shock attenuation in the forefoot strike compared to the habitual condition for BK/A (mean Δ = 0.13, p = 0.004) and AK/A (mean Δ = 0.23, p = 0.007). No significant differences were found for AK/BK or vertical shock attenuation. These results suggest that shock attenuation may not reflect joint-specific loading changes that have been shown for forefoot striking (i.e., increased ankle/shank and decreased knee moments). However, it may capture changes in overall lower extremity loading (i.e., decreased vertical ground reaction forces).