## 4 Discussion
### Biomechanical Gait Pattern of Elderly People with Lower Cognitive Function  
Although statistical significance between the two groups did not appear in the spatiotemporal parameters, the LC group showed lower gait performance compared to the NC group (Table 2). However, subdivisions of the gait cycle showed significant differences between the LC group and the NC group (Table 3). Compared with the NC group, the LC group had a shorter SLS and longer DLS, which was attributed to the change in the ratio of the LR and the MSt. The LC group showed a longer LR and shorter MSt than those of the NC group. Considering that only cognitive function showed a statistically significant difference between the two groups (Table 1), this means that the neuromotor control of the gait is different according to the status of cognitive function.  
In the LR, the LC group showed lower knee extensor moment and power than the NC group, whereas the hip joint showed higher extensor power (Figure 1). During the LR, tasks such as weight shifting and shock absorption are performed and, if these tasks are unsuccessful, a fall may be induced. The work of the concentric contraction of the knee extensor for shock absorption [23] was small in the early LR (i.e., mKPP-0 in Table 7). To compensate for this, the positive work of the hip extensor was in a burst (i.e., pHP-1 in Figure 1g).  
In the MS, the hip extensor work of the LC group was rapidly decreasing, unlike the maintained hip positive power of the NC group (Figure 1g). In particular, the LC group presented lower knee extensor moment and power than the NC group (Figure 1e,h). Although there is no statistical significance, it can be seen that the mKEM and mKPP-1 of the LC group are lower than in the NC group, as shown in Tables 6 and 7. During the MSt, the upright alignment of the segments of single-leg movement that supports the body must be achieved and maintained. Therefore, the low knee extensor moment and power of the LC groups means that the activation of the knee extensors of the LC group is lower than in the NC group. In other words, this means that the quadriceps muscle function was lower in the LC group than in the NC group. [PERSON] et al. [24] reported that the function of the quadriceps muscles decreases with aging. This low activation of the knee extensor can merely be regarded as a result of aging, but there was no statistical difference in age between the two groups. In other words, elderly people with cognitive decline show lower knee extensor function than elderly people without cognitive decline.  
In the second half of the stance phase (i.e., the TSt-PSw), the LC group presented more dorsiflexion and lower hip flexor power. pAA-2 and AAD-1 in Tables 4 and 5 show that the ankle joint is flexing more in the LC group than in the NC group from the TSt to PSw. This dorsiflexion leads to a faster initial contact of the contralateral limb and might contribute to the reduction of step length, as shown in Table 2. In addition, pHP-3 and mHPP-2 were lower in the LC group. Given that mHFM was similar between both groups, it can be presumed that the angular velocity of the femur, which is flexing when entering the swing phase, is lower in the LC group and thus contributes to a decrease in stride length. This can be attributed to the reduced positive power of plantar flexion in the PSw (Figure 1i).  
To summarize, significant differences between both groups were found in the subdivisions of the gait cycle. Furthermore, biomechanical differences were also found. The LC group has a longer DLS and LR and shorter SLS and MSt than the NC group. In the LR, MSt, and push-off, the extensor activity of the three lower-extremity joints was different between the two groups.