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

Context: Three foot-strike techniques are common in runners. If these techniques generate different sounds at the point of impact with the ground, lower limb kinetics may be influenced. No previous authors have determined whether such relationships exist. Objectives: To determine foot-ground impact sound characteristics and 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: A total of 30 runners (15 women, 15 men; age ¼ 23.5 6 4.0 years, height ¼ 1.67 6 0.1 m, mass ¼ 58.1 6 8.2 kg) completed overground running trials with rearfoot-strike, midfoot-strike (MFS), and forefoot-strike (FFS) techniques in a gait analysis laboratory. Main Outcome Measure(s): Impact sound was measured using a shotgun microphone, and the peak sound amplitude, median frequency, and sound duration were analyzed. Separate linear regressions, clustering participants due to repeated measures, were used to compare the sound characteristics across foot-strike techniques. Kinetic data were collected from a force plate, and the vertical loading rates were calculated. Pearson correlation was used to determine the relationship between sound characteristics and kinetics. Results: Landing with an MFS or FFS resulted in greater peak sound amplitude (P, .001) and shorter sound duration (P, .001) than a rearfoot strike. The MFS exhibited the highest median frequency among the 3 foot-strike patterns, followed by the FFS (P, .001). We did not find a significant relationship between vertical loading rates and any impact sound characteristics (P . .115). Conclusions: The results suggest that impact-sound characteristics may be used to differentiate foot-strike patterns in runners. However, these did not relate to lower limb kinetics. Therefore, clinicians should not solely rely on impact sound to infer impact loading.