## 4 Discussion
[29] investigated the effect of shoes with various heel lifts relative to forefoot (0 mm, 4 mm, 8 mm, and 12 mm) on running biomechanics and found no systematic changes across heel lifts. While no significant difference was found between the large (12 mm) and small (0 mm) heel lift conditions, the authors found that the medium heel lift condition (8 mm) was significantly higher foot strike angle than small heel lift (0 mm) and significantly longer stride length than the large heel lift (12 mm) in self-preferred speed running. When heel lift increases, the windlass effect is activated and produced a relative shortening of longitudinal arches that is suggested to alter the plantar loading and joint positioning transmitted from the rearfoot to the forefoot [16]. These changes of joint kinematics lead to different relative points of force application and shift the GRF vector, resulting in the similar pattern with rearfoot and knee moments in our study. Our results, along with previous findings, suggest that optimal range of heel lift seems to exist to optimize running mechanics and performances. Wearing arch-support orthoses lead to smaller peak rearfoot version moment but larger peak knee extension moment when compared to wearing flat orthoses. This is in line with previous studies [56; 57], which suggested that wearing foot orthosis reduced peak rearfoot version moment but increased peak knee extension moment. Foot orthosis with arch-support could sustain the medial longitudinal arch and control excessive promotion [56]. The significant reduction in the peak ankle version moment facilitated by the orthosis could alleviate further pronation and progression [56; 58], which could be difficult to obtain by surgical intervention alone [59]. On the other hand, the larger extension moment when wearing arch-support orthoses could be resulted from restricted plantarflexion of ankle [57]. [PERSON] and his colleagues [60] stated it is possible that increasing the knee extension moment could be deleterious to patellofemoral dynamics. However, in the studies of [PERSON] et al. study [56] and [PERSON] et al. study [57], only participants with flatfoot and post-stroke hemiplegia were recruited. Hence, further studies may consider conducting studies on the use of arch-support orthoses by injury-free and healthy participants before a viable conclusion can be made. When interpreting our results, it is important to consider several limitations in our study. Firstly, only male habitual rearfoot strikes were recruited in this study. The findings may not be generalizable to habitual midfoot/forefoot strikers and female population as biomechanical data differ across various foot strikes and between gender. Females are expected to have larger Q-angle and lower heel pad stiffness that may predispose distinct biomechanics pattern and loading characteristics and thus different running injuries [14; 17; 22; 61]. Secondly, we did not measure comfort perception variables. Comfort perception has been received considerable interest by coaches and sports scientists as increase in perceived comfort was related to better running economy [7] and impact attenuation and performance during running [62]. Thirdly, we compared a large number of biomechanical variables to provide a comprehensive analysis of the orthotic effect in running. There is an increased chance of type I error when interpreting our study findings. Fourthly, while there are well over 40 different ways of foot type classification and there is no international standard on which method is the most appropriate [63], our study screened the participants using only single foot type classification method and instructed the participants to run with their preferred running speed. It should pay particular attention when comparing the orthotic effects across the studies which had different foot type classification methods and running speeds. Finally, the study was conducted without using incorporated arch-support on different medial-lateral wedge orthoses.