Prefrontal cortex responses to different footwear comfort conditions: a feasibility study using functional near-infrared spectroscopy

Existing evaluation for footwear comfort relies on subjective self-reported measures like questionnaires, while objective neurophysiological real-time indicators have not been established yet. Even though functional near-infrared spectroscopy (fNIRS) signals on the prefrontal cortex have been investigated during locomotion tasks, there is limited research on the effects of footwear comfort levels on brain response using fNIRS. This study aims to investigate the effect of two varying footwear comfort conditions (manipulated by shoe size) on prefrontal cortex activation while walking, and to determine whether it is possible to distinguish between more comfortable and less comfortable footwear through prefrontal cortex fNIRS measurements. Twenty-seven participants walked at a set speed of 5 km/h while wearing less and more comfortable footwear to elicit differences in their perceived comfort level. Their prefrontal cortex real-time activation was recorded by a 15-channel fNIRS device. Signals from 23 participants were analyzed, because four participants failed to distinguish the comfort differences between the two shoes. Statistical analyses were performed on averaged oxy-Hb and deoxy-Hb concentration changes of subdivided walking task phases to compare the two footwear comfort conditions. For the more comfortable condition, data showed significantly enhanced hemodynamic responses, reflected by increased oxy-Hb levels and/or decreased deoxy-Hb levels in channels 2, 3, 11, 12 and 14, which are located in the left and right dorsal prefrontal cortex (dlPFC) and the left frontopolar prefrontal cortex (FPC). In conclusion, comfort level of footwear may influence prefrontal cortex activation, as observed through fNIRS measurements. The present study implies the possibility to distinguish more (or less) comfortable footwear through prefrontal cortex hemodynamic analysis, which may provide a novel method for footwear comfort evaluation.