The use of multi-directional footfall sound recordings to describe running vertical impact properties

This study investigated whether the use of multi-directional sound recordings could provide sound amplitudes of superior quality for the assessment of vertical impact properties during running. Thirty-four young adults performed overground running at the preferred speed (HS) and while intentionally reducing volume of footfalls (LS). Ground reaction forces and sounds from four microphones surrounding the force platform were recorded. Vertical loading rate, foot strike pattern and peak sound amplitudes from anterior, posterior, medial, and lateral recordings were analysed. Peak vertical force(a), peak propulsion force(b) and running speed(c) showed significant correlations with peak sounds from anterior microphones during HS (r_a = 0.35, r_b = -0.49, r_c = 0.61). Conversely, these variables were correlated with peak sounds from posterior microphones during LS (r_a = 0.39, r_b = -0.50, r_c = 0.70). Moreover, the sensitivity in determining changes in peak sounds vary across microphone locations, as reductions in peak sounds during LS varied from 31% and 49% across locations. Therefore, the relationships between running sounds and force parameters can be highly influenced by the number and location of microphones. Furthermore, anterior and posterior sound perspectives reveal the most significant interactions between sound and force parameters.