Discussion
The results of the present study show that middle-aged subjects were more affected by the reduced light condition compared with young and old adults. Similar to old adults, middle-aged participants increased their stride time variability when walking in near-darkness, but were the only ones who increased lateral variability and anterior/posterior variability in near-darkness, whereas gait variability of young adults was not affected by the light condition. In addition, middle-aged individuals showed increased lateral variability in both lighting conditions compared with young adults.Our findings may suggest that age-related changes beginning in middle age impair the ability to regulate gait stability when visual perception is limited due to diminished lighting. Decreased ability of the somatosensory and vestibular systems to compensate for visual input has been suggested as a reason for slow walking speed and decreased postural instability under limited lighting conditions in the elderly population [In contrast to our findings, Reynard and Terrier [Another study that may not agree with our findings is the study by Kesler et al. [Performing an additional task simultaneously with walking did not affect gait stability in either age group under both normal and reduced light conditions. The literature on the effects of cognitive tasks on gait variability in healthy individuals is inconclusive. Some studies show a destabilizing effect, especially in the elderly [Although stability during walking was not affected by the additional cognitive task, serial 7 performance of older adults was lower than that of young adults during walking, whereas it did not differ during sitting. This result is consistent with the "posture-first" principle, which has shown that older people prefer to maintain stability when walking while performing another task [This study has several limitations. Our middle-aged group included subjects aged 45 to 65 years. Although middle age is associated with this stage of life, human performance can vary widely during this period. We believe that the results of the present study shed light on the effects of reduced lighting on gait stability in middle age. Nevertheless, future studies with a larger and varied sample may allow analysis of age subgroups within middle age. Another limitation of our study is that it was conducted in an indoor laboratory setting while subjects walked on a treadmill wearing a safety harness. It has already been shown that a non-weight-supporting harness does not alter gait dynamics [