April 2019

Peak Tibial Accelerations as Real-time Measure of Impact Loading

Figure 1: At the common running speed of 11.5 km/h, [left] the 1D peak tibial acceleration (encircled) is about 7 g. [right] The 3D peak tibial acceleration is always greater, reaching almost 10 g during foot-ground contact. Image is complements of the author. Image provided by author.

By Pieter Van den Berghe

Studies seeking to determine the effects of gait retraining through biofeedback on peak tibial acceleration (PTA) assume that this biometric trait is a valid measure of impact loading that is reliable both within and between sessions. However, data was lacking for the validity and reliability of these measures at the speed of endurance runners.

To test the issue, researchers at Ghent University in Belgium developed a wearable system that accurately measures and monitors impact loading in endurance runners in real-time. The system consists of a lightweight 3D accelerometer, which attaches to the runner’s legs, and an application for the real-time detection of PTA. The system was compared to stationary lab equipment.

The researchers, from the Biomechanics of Human Movement Research Group, tested 13 rearfoot runners at various speeds over 2 sessions, which required re-attachment of the system (see Figure 1). Their findings were reported in the January 2019 issue of the Journal of Biomechanics.

The team found moderate to strong correlations between the wearable system and the criterion measure (Figure 2). Although other studies have linked the axial component of peak tibial acceleration to a lab-based measure of impact loading, none had done so for the resultant component. Impact loading measures remained similar between both running sessions. The wearable system provides valid and reliable surrogate measurements of impact loading in real-time, from a few steps to complete training sessions in- or outside a sports laboratory or clinical environment.

We believe our study on shocks impacting the lower extremity is of interest for practitioners and scientists in the fields of physical therapy and sports medicine. What is really interesting is that the wearable system permits synchronization to motion capture and comes with biofeedback modality.

Figure 2: Time series of (a) axial and (b) resultant tibial accelerations. Averaged signals of unfiltered tibial acceleration during the stance phase of running at 2.55 (blue), 3.20 (green) and 5.10 (red) ms1. Stance was normalized to mean contact time. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article at www.sciencedirect.com/science/article/pii/S0021929019300764?via%3Dihub). Reprinted with permission from Elsevier Ltd. All rights reserved.

Pieter Van den Berghe is a doctoral researcher in the Department of Movement & Sports Sciences,  Biomechanics of Human Movement research group, at Ghent University in Belgium. The group focuses on understanding the neuromechanical interaction of the moving body and the environment to answer questions related to the optimization of learning processes, (sports) performance, and musculoskeletal loading. By collaborating with the institute for systematic musicology at Ghent University, a research project on over-ground running retraining by means of music-based biofeedback on impact loading was initiated. The study described above is the first milestone achieved by the multi-disciplinary team. Preliminary findings were presented at the 2018 World Congress of Biomechanics.

Source: Van den Berghe P, Six J, Gerlo J, Leman M, and De Clercq D. Validity and Reliability of Peak Tibial Accelerations as Real-time Measure of Impact Loading During Over-ground Rearfoot Running at Different Speeds. J Biomech. 2019:86:238–242.

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