Comparing the Force–Time Characteristics Between Countermovement and Assisted Countermovement Jump with Different Landing Strategies

Researchers comparing countermovement (CMJ) and assisted countermovement (ACMJ) jumps reported conflicting findings on the landing impact force (LIF). This was likely due to differences in the landing strategies used. As the magnitude of LIF may have implications on neuromuscular adaptations, the purpose of this study was to compare the LIF between CMJ and ACMJ while adopting soft and stiff landing strategies. Thirteen resistance-trained athletes (sex: female = 5, male = 8, 26.4 ± 3.7 years, 68.4 ± 13.6 kg, 167 ± 5.1 cm) performed three CMJ and ACMJ each at 60%, 70%, 80% and 90% of bodyweight with instructions to either land soft or stiff on a force plate. Repetitions were separated by 30 s and conditions by 3 min. Resistance bands were used to induce the required weight during ACMJ. Data obtained regarding the average of the two closest trials based on jump height was analysed. Jump height significantly increased with increasing assistance during ACMJ for both landing conditions (<i>p</i> < 0.001). Propulsion duration (PD) was significantly shorter with increasing assistance during ACMJ for both landing conditions (<i>p</i> < 0.001). Peak and mean propulsion force significantly decreased with increasing assistance during ACMJ for both landing conditions (<i>p</i> < 0.001 and <i>p</i> < 0.001, respectively). The LIF was significantly greater with increasing assistance during ACMJ in the stiff-landing condition only (<i>p</i> < 0.001). Greater assistance allowed participants to jump higher while reducing PD. The higher LIF observed during stiff landing with greater assistance during ACMJ could be attributed to greater jump height and downward velocity during landing.