Acute effects of different loading protocols upon performance and kinematics of 180 degrees change of direction

This study examined the acute effects of different loading protocols on 180 degrees change of direction (COD) performance in eleven male handball players. Participants performed a 10-0-5 COD test under seven conditions: without an external load, and with 3, 6, and 9 kg loads applied under two modes-assisted into the COD and resisted out of it and resisted into the COD and assisted out of it. While total COD time was not affected (p = 0.098; eta(2) = 0.16), significant phase effects were observed (p < 0.001; eta(2) >= 0.55). Loading protocols significantly influenced velocity, acceleration, and their distances from COD (p < 0.001; eta(2) >= 0.37). Significant phase effects were observed for all step kinematic variables (p <= 0.037; eta(2) >= 0.67), except contact time, and significant interaction (phase*condition) effects for all variables (p <= 0.004; eta(2) >= 0.08), except for step frequency. Assisted-resisted protocols increased deceleration demands through higher COD entry velocities, displaying fewer but longer steps in the acceleration phase and greater steps taken during the deceleration phase. Resisted-assisted protocols decreased deceleration demands due to lower COD entry velocities, displaying shorter, but more steps taken in the acceleration phase, and fewer steps taken in the deceleration phase. These findings suggest that assisted-resisted and resisted-assisted loading protocols can be used to selectively overload specific phases of COD performance.