Relationships Between Tibial Accelerations And Ground Reaction Forces During Loaded Walking

Peak vertical and resultant tibial accelerations (vTAs, rTAs) during running are strongly related with early stance vertical ground reaction forces (GRFs), which in turn are associated with musculoskeletal injury. Given this, peak vTAs are often used as a surrogate of forces in the absence of a force plate. However, few studies have examined these correlations during walking, and none have reported on walking with loads, a key activity leading to injury in the military. Peak rTAs may also be related to posterior GRFs, which have shown some association with injury. PURPOSE: To determine the correlations between vertical/posterior GRFs and TAs during loaded walking METHODS: 461 US Army trainees participated. An inertial measurement unit (IMU) was attached over their distal antero-medial tibia. Participants walked on an instrumented treadmill at 1.2-1.3 m/s with an Army-issued pack loaded with 18.1 kg, for a 3-min warm-up and 16 s of data collection. Impact variables were averaged over 7 strides. Pearson correlations were calculated for peak vTAs/rTAs with vertical load rates (VLRs) and 1st peak force. Due to the position of the IMU, posterior GRFs were correlated with peak rTAs, as opposed to posterior TAs. RESULTS: The highest correlations were between VLRs and peak vTAs. However, these correlations were lower than has been reported for running (r > 0.7), and the variance explained was low (28-29%). While significant, correlations between posterior GRFs and rTAs were low. CONCLUSION: Our results show moderate correlations between vTAs and vertical load rates during walking with loads. Further studies are still needed to determine the utility of TAs during loaded walking for injury risk prediction and targeted feedback to lower load rates through gait retraining. Supported by US DoD award W81XWH-20-C-0123 P0001. The opinions/assertions in this manuscript are the private views of the authors and are not to be construed as official policy or reflecting the views of the US Army.