Use Of Inertial Magnetic Sensors To Implement Kinematic Methods To Detect Foot Contact During Running

Abstract

Biomechanics of the stance phase of running is of interest in relation to injury development. Studying the stance phase requires proper detection of foot contact (FC). The onset of vertical ground reaction force (GRF) is considered the gold standard in a laboratory setting to detect FC. In the absence of GRF data, motion analysis can be used to measure peak downward velocity of the pelvis (PDVP) with a 15ms offset which showed good relation with FC during treadmill running at one speed (1). Inertial sensors can measure kinematic parameters like PDVP outside the laboratory setting. Peak tibial acceleration (PTA) is a parameter of interest in running injury development which can be measured with inertial sensors and may also be used to detect FC outside the laboratory. PURPOSE: To assess the effectiveness of these kinematic methods using inertial measurement units (IMUs) to detect FC during running at different speeds. METHODS: 3 male runners (28 ± 8.5 yrs) ran on an instrumented treadmill at 6 speeds (10-15 km/h) for 1 minute each, wearing a suit equipped with IMUs at the tibia and sacrum. FC was determined based on GRF data of the treadmill (1000 Hz; threshold of 20N) and IMU data (240Hz). PDVP was obtained from a single integration of pelvic acceleration in the global frame. PTA was determined from the acceleration data measured in the local tibia frame. The 95% limits of agreement were used to compare each method to the gold standard (i.e., GRF). RESULTS:Table 1: The offset and 95% limits of agreement for the two kinematic methods with respect to the gold standard for 6 running speeds.CONCLUSION: This study showed that a novel IMU-based method of detecting FC using PTA and PDVP showed good similarity with FC detection based on GRF at all running speeds. The different time offsets among running speeds should be considered when implementing these kinematic methods to detect FC. This opens up new possibilities for studying running mechanics outside the laboratory. REFERENCES: 1. Milner CE, Paquette MR. A kinematic method to detect foot contact during running for all foot strike patterns. J Biomech. 2015. 18; 48(12): 3502–5