Force Orientation on Changes of Direction: A Kinetic Comparison of the Penultimate, Final, and Acceleration Steps During a Modified 505 Test

ABSTRACT: Barrera-Domínguez, FJ, Paul A. Jones, Almagro, BJ, and Molina-López, J. Force orientation on changes of direction: A kinetic comparison of the penultimate, final, and acceleration steps during a modified 505 test. J Strength Cond Res XX(X): 000-000, 2026-The knowledge of the mechanical variables in the different phases of change of direction (COD) actions would provide useful data for improving the performance of multidirectional movements. The purpose of this study was to investigate the relationships between different mechanical characteristics and ground reaction force (GRF) orientations of the COD during penultimate (PFC), final (FFC), and first accelerating foot contact (AFC) with both performance and efficiency of COD. Twenty-five multidirectional male athletes (age, 23.5 ± 3.27 years; body height, 178 ± 9.76 cm; body mass, 79.4 ± 14.7 kg) performed 6 modified-505 trials, and GRFs were collected across the PFC, FFC, and AFC during the COD. Players were categorized as "Low-Group" (n = 13) and "High-Group" (n = 12) based on performance and efficiency in COD. Faster and more efficient performers demonstrated significantly lower vertical impact forces (VIF) in PFC (R2 ≥ 0.16; p ≤ 0.04), shorter ground contact times (GCT) in FFC (R2 ≥ 0.15; p ≤ 0.04), and greater horizontal propulsive force (HPF) during AFC (R2 ≥ 0.45; p < 0.01) than slower athletes. These findings suggest that different mechanical properties are required to produce faster and more efficient multidirectional speed performance. Training focused on developing the athletes' COD technique and stretching shorten cycle function to minimize VIF, shorten GCT, and increase HPF may be advantageous for turning performance.