Impact sound across rearfoot, midfoot, and forefoot strike during overground running

Context: There are three common foot strike techniques in runners. Whether these techniques generate different sounds at the point of impact with the ground may influence lower limb kinetics. No previous studies have determined whether such relationships exist. Objectives: To determine foot-ground impact sound characteristics and to compare the impact sound characteristics across foot strike techniques and the relationships between impact sound characteristics and vertical loading rates. Design: Cross-sectional study Setting: Gait analysis laboratory Patients or Other Participants: Thirty runners (50% female, age=23.5±4.0 yrs, mass=58.1±8.2kg, height=1.67±0.1m) completed overground running trials with rearfoot strike (RFS), midfoot strike (MFS) and forefoot strike (FFS) techniques in a gait analysis laboratory. Main Outcome Measure(s): Impact sound was measured by a shotgun microphone and the peak sound amplitude, median frequency and sound duration were analysed. Separate linear regression, clustering participants repeated measures were used to compare the sound parameters across foot strike techniques. Kinetic data was collected from a force plate and the vertical loading rates were calculated. Pearson's correlation was used to determine relationship between sound characteristic and kinetics. Results: Landing with a MFS or FFS resulted in greater peak sound amplitude (ps<0.001) and shorter sound duration (ps<0.001) than RFS. MFS exhibited the highest median frequency among the three foot strike patterns, followed by FFS (ps<0.001). We did not find a significant relationship between vertical loading rates and any impact sound parameters (ps>0.115). Conclusions: The results suggest that impact sound characteristics may be used to differentiate foot strike patterns in runners. However, this did not relate to lower limb kinetics. Therefore, clinicians should not solely rely on impact sound to infer impact loading.