###### Abstract
[26] showed that the reduction of toe flexor strength and the presence of toe deformities increased the risk of falling among older people. [PERSON] et al. [27] investigated the relationship between walking ability and falls in elderly Japanese people. Their results showed that lower toe-gap force was significantly associated with falling. [PERSON] et al. [28] presented a study showing that timed up-and-go test (a measure of functional ability) results were significantly correlated with toe grip strength. [PERSON] et al. [29] assessed the effect of toe flexor exercises on apical plantar pressure, and showed that such exercises can improve forefoot stability and gait efficiency. [PERSON] et al. [30] showed that the toe elevation angle of participants who had experienced a fall was significantly smaller compared with that of participants who did not fall. Plantar pressure is another important indicator in walking evaluation, such as for the diagnosis and determination of the course of a disease. [PERSON] et al. [31] showed that the claw/hammer toe deformity is associated with a distal-to-proximal transfer of load in the forefoot, and elevated the plantar pressure at the sub-metatarsal heads in neuropathic diabetic patients. [PERSON] et al. [32] developed predictive models to identify the potential etiological factors associated with elevated plantar pressure. [PERSON] et al. [33] investigated the factors associated with increased plantar pressure on the diabetic foot. [PERSON] et al. [34] compared plantar pressure among healthy individuals with normal, planus, or cavus feet. [PERSON] et al. showed that high plantar pressure may increase the risk of falls. However, the above observation methods can provide only specific data, including pressure or IMU data; thus, they yield a limited amount of information. Examples of unobservable information obtained by conventional measurements include accurate contact area, skin deformation, and skin color. It is difficult for pressure sensors to detect or identify the exact contact area when the load is low (for example, during the swing phase). Thus, we propose a novel wearable sensing system for direct observation of the plantar aspect while walking on any surface and condition [35]. The plantar image is reflected by a reflective film and captured by a camera embedded in a clog (shoe). Passive joints are embedded in the camera holder and around the tarsometatarsal joints to facilitate walking while wearing the system. However, the main contribution of this sensing system is the investigation of fall or stumbling risks, which were not considered previously. As a first step, we focus on toe activity, which is closely related to walking issues such as stumbling, which in turn is directly connected to falling [36; 37]. We did not find research that collected and analyzed visual data on toe movements in the above literature, because of the difficulty in directly obtaining visual data from the sensor. The utilization of the developed system is expected to provide clearer information on toe movements, especially in the swing phase. The movements in the swing phase are difficult to observe by conventional IMU or pressure sheet sensors. In this study, we investigated the relationship between toe-area activity and stumbling utilizing the developed sensing system. Specifically, we identify the features of toe-area activity while walking in elderly people with a history of stumbling. The main difference of this study from the previous one [35] is the utilization of the sensing system. The previous study provided only primary results among young male participants, whereas this study investigated the effects of aging to identify new features of walking in elderly people with a stumbling history. We also improved the sensing system.