Effects of stochastic resonance on reflexive and perceptual outcomes in chronic ankle instability

Introduction Abnormal lower-limb cutaneous reflex characteristics following stimulation during gait have been observed among those with chronic ankle instability (CAI), which have been linked to perceptions of instability. These outcomes have the potential to serve as biomarkers of CAI or functional measures of sensorimotor recovery following lateral ankle sprain or clinical rehabilitation. However, no studies, to date, have identified a targeted intervention to regulate cutaneous reflexes in this population. Therefore, the purpose of this study was to explore the effects of stochastic resonance (SR) on lower-limb cutaneous reflexes and perceived instability during gait in those with CAI and healthy controls. Methods Participants walked on a treadmill at 4 km/h while receiving random, non-noxious sural nerve stimulations throughout the stance phases of gait, reporting their perceived instability following each stimulation on an 11-point numeric rating scale. Mixed-factor ANOVAs were used to determine if a subthreshold stimulation applied to the ankle via an SR device affected ipsilateral lower leg reflexes and perceptions of ankle instability between groups. Results Results indicate that the CAI group exhibited elevated PL facilitation and gastrocnemius reflex variability during midstance as well as increased perceptions of instability following sural stimulation. Discussion SR may enhance consistency of cutaneous reflexes and reduce perceptions of instability following sural stimulation among those with CAI, indicating this intervention should be explored in a clinical setting as an accessible intervention to improve sensorimotor and patient-reported outcomes.