###### Abstract
Compared with landing using both legs, previous studies have shown that landing with a single leg will increase knee and hip flexion and extension moments, peak VGRF and power, which result will increase tension and stress of the knee ligament, thus increasing the risk of ACL injury [21; 22; 23]. However, there is a lack of research on the biomechanical differences caused by volleyball players landing on a single-leg after a spike, and it is also not clear that landing following a volleyball spike would make a greater difference than a typical landing. The injury risk of volleyball players while jumping and landing is determined by the spatial and temporal characteristics of the sport. This has been observed especially during landing after blocking and spiking and increases the probability of ACL injury of volleyball players [24]. In landing tasks, previous studies have shown that ACL injury is believed to occur 30-50 ms after initial ground contact [21]. In the biomechanical analysis of landing tasks that may cause damage, the timing of post-landing damage needs consideration. However, current kinematic and kinetic analyses only partially focus on the peak point data and assume that the peak point time in line with the critical time at the injury occurs. [PERSON] and [PERSON] et al. compared and analyzed the peak joint angle and moment (knee and hip flexion, knee and hip moment) between single-leg and double-leg landing tasks [25; 26; 27; 28]. Most of them focus on analyzing peak data. [PERSON] and [PERSON] et al. also compared the peak VGRF and peak knee proximal tibia shear force during different landing tasks [19; 29; 30]. This analysis method is widely accepted in research, but the comparative peak misses the important time fluctuations that may happen in the whole landing phase. At present, great progress has been made in the study of biomechanics spatial and temporal variability, and a relatively complete model framework has been presented [11; 31; 32]. Statistical parametric mapping (SPM) is a method, which can test the statistical differences of continuous data such as kinematics and kinetics over the whole period of motion to calculate accurately the significance threshold [33; 34]. Therefore, based on the one-dimensional character of joint motion changing with time, combining traditional discrete analysis with statistical parametric mapping of one-dimensional (SPM 1d) was used to conduct statistical analysis on the sagittal biomechanical data of the landing task of volleyball players. This can reveal ACL injury mechanics of volleyball players during landing tasks after a spike and provide injury prevention strategies. Therefore, the main aim of our study was to investigate the VGRF and kinematics and kinetics of the lower extremity sagittal plane movement in the whole landing stage of volleyball players following a spike landing with single-leg landing (SL) and double-leg landing (DL). This will be achieved using traditional discrete kinematic and kinetics analysis and statistical parametric mapping of one-dimensional (SPM 1d) analysis. We hypothesized that significant biomechanical differences may be observed in the sagittal plane between SL and DL after a spike. Compared with DL, the SL could show smaller knee and hip flexion angles and angular velocities as well as greater moment, power, VGRF and loading rates. Meanwhile, most of these differences may be observed within the 30-50 milliseconds time frame of initial contact with the ground. Our hypothesized results may provide some clues to reveal the injury mechanism of ACL from the temporal kinematic and kinetic differences during landing phase.