# Effects of Toe-Out and Toe-In Gaits on Lower-Extremity Kinematics, Dynamics, and Electromyography
## 4 Discussion  
This study used the experimental measurements and musculoskeletal modeling to study and compare the effects of toe-in and toe-out gaits at normal walking speeds on the lower-extremity kinematics, dynamics, and EMGs. The results showed that the toe-in and toe-out gaits indeed influenced these values, especially on the joint moments and EMGs. This study also showed that the peak value of JRFs does not decrease with reducing peak KAM, which is consistent with previous research findings [35]. Gait modification changed moments and angle of joints; for example, the toe-in gait changed joint rotation angles at the ankle and hip joints, as shown in Table 1, and knee adduction moments at knee joint, as shown in Figure 5. The obtained joint angles and joint moments during the natural gait are slightly different from those reported by [PERSON] et al. [25], who used the IK and residual reduction algorithm (RRA) tool to calculate joint angles during a running gait. Both the toe-in and toe-out gaits have no statistically significant effects on reducing the peak values of GRFs in the three directions except for the second peak ML force in the toe-out gait, as shown in Table 2.  
EMG is used to detect and assess muscle coordination and activation levels; EMG signal across different gaits may be able to provide insight into muscular force production and function of individual muscles during movement. The use of EMG has been controversial because of considerable variations between subjects; however, it still has reference value in individual cases where a baseline has been established. The EMG profiles recorded for the knee-crossing muscles revealed there were differences in EMG activations among the three gait patterns. As shown in Table 3, the toe-in and toe-out gaits resulted in higher values for quadriceps and peroneus longus; however, they reduced EMG values for biceps femoris and gastrocnemius lateralis. The toe-in and toe-out gaits resulted in the opposite effect on the activations of tibialis anterior, semitendinosus, and gastrocnemius medialis. Many studies suggested that an elevated KAM value represents an elevated TF contact force or medial TF contact force, which has been considered as one of the important contributors to knee osteoarthritis [36; 37; 38]. The toe-out gait increased the first peak KAM and decreased the second peak  
Figure 6: Knee joint reaction forces (JRFs; mean and standard deviation) calculated from the musculoskeletal model for the natural, toe-in, and toe-out gait patterns (12 participants and 5 trials for each gait patterns). KAM, as shown in Table 4, which is consistent with the existing literature [9]. The second peak value of the KAM, as shown in Figure 5, is higher than the first peak which is inconsistent with those in the literature during the natural and toe-in gaits. It might be due to variations in the placement of markers and because healthy individuals were measured in this paper while other studies measured subjects with OA or TKA [14; 17; 35]. However, the results in Figures 4 and 6 showed that the toe-in and toe-out gaits had little effects on the GRFs and TF joint contact forces (\(p>0.05\)) but that it has significant influence on the KAM and KFM during the stance phase (\(p<0.05\)), as shown in Figure 5. The toe-in and toe-out gaits, on the one hand, are able to relieve pain by laterally changing the center of contact location [31; 39; 40]. On the other hand, a shift in the bilateral contact point locations caused by the gait patterns also has a direct effect on the lower limb joint moment and redistribution of TF contact forces [41]. Based on the results of significant changes in KAM, KAM or a combination of KAM and KFM can be used as surrogate measures for TF medial contact force but not total contact force. Although very good outcomes were obtained in this paper, there are a number of shortcomings that should be addressed in future studies.