## 4 Discussion  
This study determined the temporal errors of heel contact from the presentation of the metronome beat in the elderly and young adults. In addition, differences in between-group and within-group temporal errors when performing additional cognitive tasks were studied. The results revealed that there were significant differences in mean and CV of the temporal errors between the young adults and the elderly under both gait conditions. Furthermore, the mean temporal errors under MET and MET + BC conditions within each group were significantly increased in both young adults (MET: 128.8 \(\pm\) 29.0 ms; MET + BC: 200.2 \(\pm\) 37.0 ms) and the elderly (MET: 156.9 \(\pm\) 52.2 ms; MET + BC: 351.0 \(\pm\) 153.9 ms). However, while the CV of the temporal errors in the elderly was significantly higher under MET + BC conditions than under MET conditions (102.4 \(\pm\) 54.0% and 50.8 \(\pm\) 22.5%, respectively), the CVs in the young adult group did not change under both conditions (26.9 \(\pm\) 8.0% and 23.9 \(\pm\) 8.9%, respectively). According to previous studies related to these results, the human body receives various sensory inputs from visual, vestibular, and proprioceptive systems while walking, and moves the joints, which are under tight regulation of the neuro-muscular-skeletal system, as required. Gait in the elderly exhibits decreased step length and symmetry compared to gait in young adults as well as an increased step time and step width. It is also known that gait variability increases with age [1,10,18]. This cause is considered to have changed the shape of the gait according to the overall compensatory adaptations as the muscle strength weakens and energy consumption increases with age [10]. According to [PERSON] et al., factors involved in gait disturbance can be broadly divided into lower-, intermediate-, and higher-level disturbances [1,19]. Based on such sequential categories, lower-level disturbances include peripheral effectors of locomotion, while intermediate-level disturbances include efferent and afferent sensorimotor pathways of the central nervous system. Higher-level disturbances include anxiety and cortical control involved in gait. According to previous studies, gait abnormality and disorder can occur due to deterioration in one or more of these categories, and even more severe disturbance may occur when performing a cognitive-motor dual-task [2,17,20,21]. In other words, gait reflects the overall state of the  
Figure 3: Cumulative distribution of the temporal errors between the metronome beat and the heel contact for each gait condition by age for all participants (15 time data bundles per bar; YG: young adults group, EG: the elderly group). neuro-muscular-skeletal system, and changes in gait are closely related to physical health. Regarding gait control, it can be seen that the movement control of the lower extremities for gait indicates the ability to accurately control and determine the position and time point of the landing foot at the target point according to the throw-and-catch theory. [15, 22]. In addition, the increase in cognitive load caused by performing additional cognitive tasks can be inferred as the difference in motion accuracy due to the difference in the cognitive-motor processing capacity [8]. From this point of view, it may be inferred that the error time of the walking time used in the results of the present study reflects the cognitive-motor processing capacity of each group according to the simultaneous cognitive task during walking of young adults and the elderly [8, 15, 22]. Therefore, gait disorders in the elderly could work as a predictor and diagnostic marker of physical abnormality due to aging. However, clinical diagnostics of aging or neuropathy using relative mean differences between subjects is yet to be attained. This calls for a clear distinction between healthy young adults and the elderly (or patients with neuropathy) [10].