## 4 Discussion
Furthermore, fatigue might increase the injury risk to the Achilles tendon which is crucial in propelling the body forward and plantarflexing the foot [15]. During the landing phase, almost all differences between pre- and post-fatigue were increased joint angles, except the peak abduction angle of the hip joint. As fatigue progressed, knee abduction increased during not only the push-off phase but also during the landing phase. In addition, an increased frontal-plane of motion of the knee joint also occurred. All these changes placed the individuals under a greater risk of injuries to the anterior cruciate ligament (ACL) [42]. After prolonged running, foot pronation increased which is an indicator of several running related injuries [19]. Regarding the kinetic changes under fatigue conditions, peak vertical GRF were not significantly different, the peak knee flexion moment and peak hip extension moments were decreased during the landing phase. Landing motions increased forces and moments to the lower limbs, and thus caused the collapse of the lower extremities [43]. Compared to post-fatigue, the peak hip extensor moment and peak knee flexor moment of pre-fatigue were increased, which indicated a stiffer landing [43]. Furthermore, a stiffer landing pattern might be beneficial in attenuating the high impulse loads [44]. Thus, we suspect that the landing pattern after fatigue might not be able to deal with the high impulse loads and increased risk of injuries. In the current study, the peak vertical GRF were not influenced by the intervention of running-induced fatigue. The peak extension moment of the knee joint was not significantly affected by fatigue, which agreed with a previous study [45]. Fatigue caused increased knee valgus moments, decreased knee flexion angles, and increased peak proximal tibial anterior shear forces, resulting in increased injury risk of the ACL [45]. According to previous researches, the changes in GRF during the fatigued motion were still controversial. [PERSON] et al. [46] found that not only the vertical and antero-posterior horizontal but also the resultant vector of these two forces were decreased during the landing phase of single leg hopping as fatigue set in. [PERSON] et al. [47] found that fatigue resulted in greater peak values of GRF and loading rate, and these changes increased the stress fracture injury risk. The type of fatigue protocols was the reason for the different changesin GRF. Different fatigue protocols influenced neuromuscular and kinematic landing performance characteristics, while the magnitudes of GRF change remained uncertain [48]. While the results of this study interpreted the changes in lower extremities after running-induced fatigue intervention, several inherent limitations should be acknowledged. First, only males were included in this study. Therefore, the results were not appropriate to apply to female populations. Once fatigued, females use a more quadriceps-dominant strategy compared to males [49]. Second, we investigated jump height and the biomechanics of lower extremities when running-induced fatigue occurred, which might help to provide insight into the performance related characteristics of the basketball match. Further studies could use a fatigue protocol utilizing sprint performance, which may be more related to basketball matches. Furthermore, participants were limited to physically active males, and other athletes might present different lower limb biomechanical profiles. Another limitation is that the FPI values were not measured post-fatigue. FPI values have been proven to contribute to increased pronation after long distance running [19]. The changes in the FPI values post-fatigue might be a potential influencing factor to the changes in lower limb biomechanics. Finally, only the peak values of variables in three planes were analyzed, and further studies may incorporate further biomechanical analysis considering greater detail and the investigation of more variables.