20 This investigation assessed whether a Technique Refinement Intervention designed to 21 produce pronounced vertical hip displacement during the kicking stride could improve 22 maximal instep kick performance. Nine skilled players (age 23.7 ± 3.8 years, height 23 1.82 ± 0.06 m, body mass 78.5 ± 6.1 kg, experience 14.7 ± 3.8 years; mean ±SD) 24 performed 10 kicking trials prior to (NORM) and following the intervention (INT). 25 Ground reaction force (1000Hz) and three-dimensional motion

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... (250Hz) data 26 were used to calculate lower limb kinetic and kinematic variables. Paired t-tests and 27 statistical parametric mapping (SPM) examined differences between the two kicking 28 techniques across the entire kicking motion. Peak ball velocities (26.3 ± 2.1 m·s -1 vs 29 25.1 ± 1.5 m·s -1 ) and vertical displacements of the kicking leg hip joint centre (0.041 30 ± 0.012 m vs 0.028 ± 0.011 m) were significantly larger (P<0.025) when performed 31 following INT. Further, various significant changes in support and kicking leg 32 dynamics contributed to a significantly faster kicking knee extension angular velocity 33 through to ball contact following INT (70-100% of total kicking motion, P<0.003). 34 Maximal instep kick performance was enhanced following INT and the mechanisms 35 presented are indicative of greater passive power flow to the kicking limb during the 36 kicking stride. 37 38 39 40 41 The maximal instep kick is an important variation of the kicking skill in soccer, as it 43 is the most commonly used technique when attempting a direct shot at goal. The ability 44 to generate a fast ball velocity represents a distinct advantage for a player when 45