The Battle Of Distal & Proximal Peak Tibial Acceleration: Inclusion Of All Acceleration Components

Abstract

Peak tibial acceleration (PTA) is considered a surrogate measure for impact forces during running and therefore associated with lower extremity injuries. Commonly, only accelerometers are used distally or proximally on the tibia for measuring PTA. Centripetal acceleration is therefore often ignored in PTA estimation distally due to an assumed low contribution or is not included at all proximally resulting in an underestimation of PTA. PURPOSE: To look into the contribution of each PTA component (longitudinal, centripetal, gravitational) for both a distal and proximal sensor during running. Furthermore, the possibility towards estimating PTA at the tibia with rigid body kinematics (RBK), independent of sensor location, is explored. METHODS: 8 recreational runners (3F/5M, running >10 km p/w > 1 year; heel strikers) ran 90 s on a treadmill at 12 kph. Two IMUs (240 Hz) were placed distal-medial (±10 cm above ankle joint) and proximally on the medial surface of the tibia, respectively, where each acceleration component (norm) of the dominant leg was calculated according to Lafortune (1991). Furthermore, with RBK, acceleration on any location on the assumed rigid tibia segment can be estimated based on one sensor to evaluate both sensor location measurements. RESULTS: Both sensors showed similar total impact acceleration including all PTA components (table 1). RBK showed greater longitudinal acceleration distally (p = 0.02) but still a similar impact acceleration (87.82 m/s2 distally vs. 80.12 m/s2 proximally, p = 0.22). CONCLUSION: Inclusion of all components is needed to accurately estimate PTA. Here, there is a similar impact PTA for both sensor locations, therefore it seems that the position does not matter if all components are included. Further research is needed to clarify and validate RBK acceleration estimations based on influence of external factors on reliability of both sensor locations and its potential towards estimating PTA at any location of the tibia.