Effects of Gender and Verbal Instruction on Soft Landing Biomechanics in Two Different Jumps

Abstract

Soft landing has been denned as increased knee flexion during landing. The details contributing to and affected by soft landing are not yet clear. PURPOSE: To determine the effect of instruction and gender on landing mechanics. METHODS: Twenty five college aged subjects were recruited. In the first session, subjects descended from vertical leaps (VL) or 50cm height drop jumps (DJ) and landed on two forceplates. In the second session, they repeated the tasks after being instructed about soft landing. Data were collected with a 3-D motion analysis system and forceplates. For each jump type, kinematic, temporal and kinetic variables were submitted to three 2 (gender) x 2 (instruction) MANOVA with repeated measures on last factor. RESULTS: Significant instruction main effects were found in all groups of dependent variables in both jumps (Table 1) and gender main effect was in kinetic variables [p=0.019] for VL. Univariate tests for instruction indicated significant increases of knee extension at touchdown (?Ktd) in VL and hip extension (?Htd) in DJ, significant increases of ankle plantar flexion (?Atd), knee flexion during landing phase OtWpA times for maximal flexion of all j oints (tA, tK, tH) and decreases of peak vertical GRF (VGRFP), axial hip joint force (AHFP) and knee extensor moments (KMF/E) in both jumps with instruction. Univariate tests for gender indicated VGRFP of males were significantly greater than those of females [14.9 ± 1.9 vs. 12.8 ± 2.5 (N/kg), p=0.03] in instruction condition of VL.Table 1: Significant multivariate and univariate tests for instructionCONCLUSION: Pre-landing extension of distal joints in VL, proximal and distal joints in DJ may activate soft landing to pre-contract muscles to prepare landing. Soft landing strategy for males can increase VGRFP which is fit for plyometrics and that of females is for absorbing type landing. Instructions given to subjects regarding soft landing may be improved by providing information about pre-planned joint stiffness and control of angular velocity of lower limb joints, in addition to increased joint excursions.