## 4 Discussion
### Effect of Drop Height on Landing Biomechanics  
The first hypothesis of this study was that the magnitude of biomechanical variables would increase with increasing drop height. This hypothesis is supported as peak vGRF and vertical loading rate of both forefoot and rearfoot, as well as peak flexion moments of the ankle, knee and hip joints, and eccentric work of the ankle, knee, and hip joints increased with the elevated drop height. The findings on kinetic variables are in good agreement with previous studies which also reported that peak vertical GRF and respective loading rate were influenced by drop height [2; 3]. The progressive increase in the magnitude of vertical loading was expected due to the increasing input energy from higher drop heights [3; 4; 11]. As participants largely adopted a toe-to-heel landing style [12; 20; 28], it is of interest to report the vGRF variables associated with the forefoot and rearfoot separately. Peak vGRF and loading rate of both forefoot and rearfoot were higher as the drop height increased, which is in line with previous work [20]. For joint kinetics, the moments and total eccentric work of the lower limb showed a significant height effect, specifically, the higher the drop height the larger the magnitude. As a large  
Figure 4: Correlation analyses of perceived landing impact with log transformed vertical loading variables across all platform height and midsole hardness conditions (106). \(\rm{r_{s}}\) denotes [PERSON]’s correlation coefficient, and was interpreted as negligible (\(0<|\rm{r_{s}}|\leq 0.30\)), low (\(0.30<|\rm{r_{s}}|\leq 0.50\)), moderate (\(0.50<|\rm{r_{s}}|\leq 0.70\)), high (\(0.70<|\rm{r_{s}}|\leq 0.90\)), or very high (\(0.90<|\rm{r_{s}}|\leq 1.00\)). knee flexion moment was reported to be associated with the increase in anterior cruciate ligament (ACL) injuries [37], athletes and coaches should be aware of the heightened risk during landing from jumps. When using DVJs as a pyjometric training exercise, previous studies recommended a drop height of no more than 0.6 m [38]. Hence, the platform heights (31 cm, 46 cm, and 61 cm) used in this study were within a safe and meaningful range. In the present study, height-dependent kinematic modifications to the landing strategy were evident only at the ankle joint, emphasizing its role in impact attenuation during landing. At the ankle joint, plantar flexion at initial contact increased with input energy (i.e., higher drop heights), allowing for a larger range of motion to support impact attenuation. This indicates that the role of the forefoot becomes more important for impact attenuation when drop height is increased. Participants adopted similar landing strategies at the knee and hip joints and kept kinematics consistent across the three drop heights. These observations are similar to the work by [PERSON] and colleagues [4] who found no height effect on sagittal plane knee ROM during drop landings. Findings from the present study also parallel the results of the study by [PERSON] and co-workers [30], in which a substantial increase in the vGRF variables but only subtle changes in the lower limb kinematics were found when increasing the drop height from 0.15 to 1.05 m. In contrast, [PERSON] et al. [3] reported a significant height effect on the sagittal knee ROM, though their reported sagittal ROM at the knee (approximately 35 degrees) was much smaller than those in the present study (around 75 degrees, Table 2) as well as in [PERSON] and co-workers' study (roughly 70 degrees) [4], thus not allowing for a plausible comparison of findings. Regarding neuromuscular response, a significant height effect was found in the increased EMG activation level across all lower limb muscles tested in the present study. These findings reaffirmed a previous study which reported higher quadriceps activation prior to landing with an increased drop height [5].