Comparison of footstrike impact sound between forefoot, midfoot and rearfoot strike

![CDATA[Rationale/Objectives: Traditionally, running coaches use the footstrike impact sound as an auditory feedback to modify running technique with an intention to reduce the impact loading and injury risk. Runners are instructed to modify footstrike pattern such that they can land quieter and softer. Interestingly, previous studies demonstrated that a quieter impact sound might not be necessarily equivalent to a softer footfall. Hence, this study compared the impact sound between forefoot (FFS), midfoot (MFS) and rearfoot (RFS) strike landings. Methods: Twenty-two runners (12 females and 10 males) completed overground running trials with three footstrike patterns (FFS, MFS, RFS) in a randomized sequence. We used a force plate to collect the running kinetics data, while a shotgun microphone was used to collect the impact sound data. The peak sound amplitude, onset time to peak amplitude, sound duration, median frequency at initial contact and peak, vertical average (VALR) and instantaneous (VILR) loading rates were calculated, averaged and compared across the three footstrike patterns. Results: In FFS and MFS, the peak sound amplitudes were higher than RFS (FFS vs RFS: p<0.001); MFS vs RFS: p<0.001) while the onset times to peak amplitude were longer (FFS vs RFS: p<0.001; MFS vs RFS: p<0.001). MFS had a significantly higher median frequency at initial contact (MFS vs FFS: p=0.025; MFS vs RFS: p<0.001) and peak (MFS vs RFS: p=0.003). There was no significant difference in sound duration (p=0.163). Biomechanically, FFS had lower VALR (FFS vs MFS: p=0.004; FFS vs RFS: p<0.001) and VILR (FFS vs MFS: p<0.001; FFS vs RFS: p<0.001). Conclusions: Non-rearfoot strikes have a louder sound, higher medium frequency and lower impact loading during running.]]