A kinematic method to detect foot contact during running for all foot strike patterns.

The biomechanics of distance running are studied in relation to both understanding injury mechanisms and improving performance. Kinematic methods must be used to identify the stance phase of running when data are recorded during running on a standard treadmill or outside the laboratory. Recently, a focus on foot strike patterns has emerged in the field. Thus, there is a need for a kinematic method to identify foot contact that is equally effective for both rearfoot and non-rearfoot strike patterns. The purpose of this study was to determine whether a new kinematic method could accurately determine foot contact during running in both rearfoot and non-rearfoot strikers. Overground gait data were collected at on 22 runners, 11 with a rearfoot strike pattern and 11 with a non-rearfoot strike pattern. Data were processed to identify foot contact from: vertical ground reaction force, two previously published kinematic methods, and our new kinematic method. Limits of agreement were used to determine bias and random error of each kinematic method compared to ground reaction force onset. The new method had comparable random error at 200 Hz sampling frequency (5 ms per frame) to the previous methods (7 frames vs 6-9 frames) and produced the same offset for both strike patterns (3 frames), while the existing methods had different offsets for different strike patterns (4 or 7 frames). Study findings support use of this new method, as it can be applied to all running strike patterns without adjusting the frame offset, simplifying data processing.