Effects of socks which improved foot sensation on velocity and stride length of elderly subjects crossing obstacles.

[Purpose] We developed socks which improve foot sensation and investigated their effect on the velocity and stride length of elderly women crossing obstacles. [Subjects] Ten community-dwelling, elderly women who could walk independently were recruited. [Methods] We measured velocity and stride length using the GAITRite system while the participants crossed obstacles under three conditions: barefoot, wearing ordinary socks, and wearing the socks which improve foot sensation.
[Results] Velocity and stride length in bare feet and when wearing the sense-improving socks increased significantly compared to their values when wearing standard socks. Velocity and stride length did not differ between the bare foot and improved sock conditions.
[Conclusion] Wearing socks helps protect the foot, but can decrease foot sensory input. Therefore, the socks which improve foot sensation were useful for preventing falls and protecting the feet of the elderly women while they crossed obstacles.

INTRODUCTION

Walking is an essential requirement for independent activities of daily living (ADLs) and quality of life of the elderly1). Effective walking requires energy efficiency to minimize fatigue, stability to prevent falls or injury, and the ability to adapt to challenging environments, such as avoiding obstacles1). Navigating obstacles is a common challenge, and the inability to maintain balance during ADLs is a frequent cause of falls among older adults2, 3). Falls occur frequently during walking, particularly while trying to avoid an obstacle or when changing direction. Falls when turning are 7.9-times more likely to cause a hip fracture than falls while walking straight ahead4, 5). Afferent sensory input signals, such as those from the visual, proprioceptive, and vestibular systems, play important roles in maintaining balance and navigating or stepping over obstacles6). Somatosensory inputs from all parts of the body contribute to postural control and body orientation6, 7). The sole of the foot is a particularly important proprioceptive input area for maintaining posture, and sensory information from the ankle is important for adjusting gait frequency and avoiding obstacles.6) In this study, we developed socks with improved foot sensation and investigated their effect on the velocity and stride length of elderly women crossing obstacles.

SUBJECTS AND METHODS

Ten community-dwelling, elderly women (mean ± standard deviation; age 64.2 ± 2.1 years; height 164.2 ± 3.2 cm; and body weight 62.5 ± 5.2 kg), who could walk independently without assistive devices, were recruited. No participant had a neurological disease, major orthopedic diagnosis (i.e., bone fracture, joint fusion or replacement, or limb amputation) in the lower back, pelvis, or lower extremities, or significant visual, auditory, or vestibular impairment. The study purpose and methods were explained to all the subjects, who provided their informed consent according to the principles of the Declaration of Helsinki before participating. Velocity and right stride length were measured using the GAITRite System (CIR System, Easton, PA, USA), which is a valid, reliable tool for measuring temporal and spatial gait parameters. The active area of the system is 61 cm wide and 366 cm long. A total of 13,824 sensors are sited 1.27 cm apart and covered with a roll-up carpet to provide a measurement area that detects mechanical foot pressure on the mat. Data from the activated sensors were collected by a computer at a sampling rate of 80 Hz, and gait parameters are identified and calculated automatically. Three obstacles, each a 28-mm-diameter, 120-cm-long steel pipe fixed to a piece of wood, were placed at a height of 10 cm on the second, fourth, and sixth pressure-activated sensor pads of the GAITRite system. The subject crossed the obstacles under three conditions: 1) bare foot; 2) wearing standard socks (G model of K company); and 3) wearing the improved sensory socks. The improved socks developed for this study were designed using a standard sock as a model (G model, K company). The improved socks had 3-mm-diameter silicone dots on the inner side of the foot surface at regular 1-cm intervals. The gait parameters for the three conditions were analyzed using one-way repeated-measures analysis of variance, followed by the post-hoc Bonferroni correction to detect differences. Differences in gait parameters among the groups were analyzed using the independent t-test; p < 0.05 was considered significant.

RESULTS

Velocity under the bare foot and improved sock conditions (64.2 ± 5.6 and 61.9 ± 9.2 cm/s, respectively) was significantly higher than that of the standard sock condition (55.1 ± 11.3 cm/s) (p < 0.05). The difference in velocity between the bare foot and improved sock conditions was not significant. Right stride length was significantly greater under the bare foot and improved sock conditions (92.2 ± 6.0 and 88.9 ± 10.8 cm, respectively), than that of the general sock condition (81.0 ± 8.6 cm) (p < 0.05). The difference in stride length between the bare foot and improved sock conditions was not significant.

DISCUSSION

In this study, the effect of foot sensory improved socks on the velocity and stride length of elderly women while they crossed obstacles was investigated. The velocity and stride length under the bare foot and improved sock conditions increased significantly compared to the standard sock condition. Gait velocity and stride length are crucial for evaluating balance control during walking by older adults, and they predict the risk of falls8, 9). When people increase their walking speed, they typically lengthen their step and increase their cadence. People use both strategies simultaneously until they reach a comfortable step length and then adjust the velocity with the cadence1). Somatosensory inputs also contribute to postural control and body orientation. The sole of the foot is a particularly important contributor to proprioceptive input and provides contact surface information for the maintenance of postural control7, 10). Sensory information from the ankle also plays important roles in adjusting gait and avoiding obstacles10). The age-related decrease in balance is influenced by inappropriate sensory input, meaning that older adults have to adopt a conservative strategy related to gait and navigating obstacles11). The bare foot condition is the best for preventing falls by elderly people. However, socks are useful for absorbing sweat when wearing shoes and allow the feet to breathe. Velocity and stride length did not differ between the bare foot and improved sock conditions. The socks with improved foot sensation had silicone dots placed on the inner side of the foot surface. The profile of the silicone dots made an important contribution to proprioceptive input and provided a contact surface information which helped subjects maintain postural control.