Effects of subthreshold electrical stimulation with pink noise on postural control in lumbar spinal stenosis: a pilot study.

Subthreshold electrical stimulation with a pink-noise structure has been shown to attenuate postural sway and improve feedback control in healthy young adults. This stimulation may benefit patients with lumbar spinal stenosis (LSS), who often experience impaired postural control. However, its effects on this population remain unclear. This cross-sectional study aimed to explore the effects of subthreshold pink-noise stimulation on postural control in patients with LSS. Sixteen patients with LSS stood quietly for 40 s with and without pink-noise stimulation. The root mean square (CoPrms) and mean velocity (CoPmv) of the foot center of pressure (CoP) in the anteroposterior (AP) direction were evaluated. The contribution of somatosensory input and strength of feedback control were evaluated using the somatosensory energy index (SEI) via wavelet transform method and the scaling exponent (Hyl) via stabilogram-diffusion analysis, respectively. Pink-noise stimulation significantly reduced postural sway (CoPrms and CoPmv) and increased SEI, indicating enhanced somatosensory engagement. While no overall change was observed in Hyl, post hoc analysis showed significantly lower Hyl in participants whose postural sway was decreased with stimulation. In conclusion, pink-noise stimulation reduced AP postural sway in patients with LSS, likely by enhancing feedback control. This imperceptible stimulation may be a valuable tool for rehabilitation.