This study aimed to investigate the immediate effect of wearing textured insoles on gait and double-limb standing balance in older people with a history of falling. Gait velocity, step length and stride length were significantly reduced when wearing the textured insoles. We did not find any significant differences between the control and textured insoles in any of the standing balance parameters.
To the authors’ knowledge, one previously published study explored the effect of a footwear intervention on gait in older fallers , showing significant improvements in gait timing variability when walking in vibrating shoe insoles. The difference between the previous work  and the current study may be related to the characteristics of the sensory stimuli. Galica et al.  used sub-threshold vibratory sensors in the insole, whilst the current study used textured insoles. In the current study, the plantar surface of the feet remained in contact with the indentations of the textured insole: this may have stimulated slow-adapting mechanoreceptors, which are reported to respond to maintained and prolonged skin indentation . In comparison, vibrotactile footwear interventions permit manipulation of the frequency, intensity, phase and duration of stimuli , and may consequently affect fast-adapting mechanoreceptors which show burst responses to stimuli, only at the point of application or removal from the foot . Vibratory stimuli may also affect intrinsic foot proprioceptors, in addition to cutaneous mechanoreceptors . It is unlikely that textured insoles work on this same principle as they provide neither mechanical nor electrical stimuli.
Furthermore, the primary outcome variables were also different between our study and Galica et al. , who measured gait variability. In the current study we did not calculate gait variability, as there is lack of consensus as to which measures of variability are most useful when quantifying changes in gait performance. The mean baseline gait speed of Galica et al.  was over 100 cm.s-1 compared to 66.3 cm.s-1 in the current study. However, baseline gait speed of older fallers in this study was similar to that reported for frail older people in previous work [30–32]. Therefore, we could speculate that older people with substantially impaired gait performance at baseline, may not benefit from this type of intervention, but for those with less impairment, footwear interventions may be more useful.
There was no significant difference of the textured insole on standing balance, unlike in our previous study with healthy older people, which showed statistically significant effects with the same texture, when used as a floor surface . It is unclear whether this is due to the delivery of the textured intervention: as a floor surface versus an insole. There is much debate relating to the effect of footwear features on postural stability. Menant et al.  reported that shoe characteristics, including an elevated heel and high-heel collar, could alter balance performance in older people. In comparison, Horgan et al.  concluded that footwear features were not associated with changes in balance scores in older women. In the current study, it is possible that incorporating a textured insole into footwear may have brought about a dampening effect of the sensory stimulus, contributing to the non-significant findings. However, the fact that participants were measured using their own shoes, and that benefits were independent of shoe types, makes the results more generalizable and relevant to daily life. Lack of agreement between the current study findings and our previous work  may also be due to differential effects between the two populations; or due to relatively greater variance in the current data masking similarly small effect sizes.
It may be that the older fallers in the current study had difficulty processing the extra sensory information, delivered through a new medium, the textured insoles, which could have constrained the sensorimotor system . It may be that the unfamiliar sensory stimulus on the plantar surface of the foot may have caused older people to walk more cautiously (with shorter steps and at a slower velocity), rather than produce an actual decline in balance ability.
The study has a number of limitations. Due to the lengthy test procedures, we did not want to risk fatigue in this first study with older fallers and, therefore, used one repetition rather than multiple trials for gait and standing balance tests. Whilst this may have resulted in relatively large measurement error in the data, it appears that the magnitude of the textured effect on gait was larger than the measurement error, suggesting this is a true finding. Our findings are specifically about the effects when the insoles were worn for the first time and should not be extrapolated outwith that context, as we did not investigate the effects of prolonged exposure to the insoles. The finding that textured insoles had an immediate effect on gait variables in older fallers supports the need for further investigation into their long-term effects.