The Relationship Between Landing Sound, Vertical Ground Reaction Force, and Kinematics of the Lower Limb During Drop Landings in Healthy Men

STUDY DESIGN: Controlled laboratory study, cross-sectional. BACKGROUND: Soft-landing instruction, which is advocated in several injury prevention programs, is thought to have a qualitative relationship with decreased vertical ground reaction forces (vGRFs) and increased lower-limb joint excursions. OBJECTIVE: To quantify the relationships among landing sound, vGRFs, and lower-limb kinematics during a drop-landing task. METHODS: Twenty-six asymptomatic men aged 18 to 35 years were asked to perform 15 single-leg drop landings from a 30-cm height. Five trials were collected under 3 sound conditions: normal, quiet, and loud. The vGRF, lower-limb kinematics (sagial plane), and impact sound were recorded during the deceleration phase. RESULTS: A simple linear regression revealed a significant relationship between landing sound and vGRF (R-2 = 0.42, P<.001). A repeated-measures analysis of variance showed that ankle and knee excursion significantly increased by 7.0 degrees and 11.7 degrees, respectively, during quiet landing (compared to normal landing; P<.001). During the loud landing condition, ankle joint excursion significantly decreased by 9.4 degrees compared to the normal landing condition (P<.001), and hip joint excursion significantly increased by 4.0 degrees compared to normal landing condition (P<.045). CONCLUSION: As landing sound decreases, so does vGRF during a drop-landing task. These reductions were achieved by increasing ankle and knee joint excursions. Conversely, as the landing sound increases, so does vGRF. This was the result of decreasing ankle joint excursion and increasing hip joint excursion.