Abstract

Objective: This study examined the effects of stochastic resonance (SR) stimulation on postural stability of subjects with functional ankle instability (FAI).

Design: Experimental research design.

Setting: Sports medicine research laboratory.

Participants: Twelve subjects with FAI who reported a history of recurrent ankle sprains and “giving way” sensations at the ankle participated in this study.

Interventions: Subjects performed 20-second single leg balance tests under SR stimulation at 0.05 mA, SR stimulation at 0.01 mA, and control conditions. Testing order was randomized. Stimulators were worn that delivered subsensory stimulation to subjects’ ankle muscles and ligaments. Subjects were blinded to test conditions, as SR stimulation was subsensory and stimulators were turned off during the control condition.

Main Outcome Measurements: Anterior/posterior and medial/lateral centre-of-pressure velocities (COPV) were combined to form a resultant vector (COPV-R). The COPV-R differences between the optimal SR stimulation and control conditions were analysed. Optimal SR stimulation was defined as the SR stimulation input intensity level (0.05 mA or 0.01 mA) that produced the greatest percent change in improving postural stability compared to the control condition. Slower velocities indicated enhanced postural stability.

Results: Nine subjects’ optimal input intensity was 0.05 mA, while 3 subjects’ optimal input intensity was 0.01 mA. The optimal SR stimulation significantly (p<0.05) improved COPV-R compared to the control condition (SR=6.60±1.06 cm/s; Control=7.20±1.03 cm/s).

Conclusion: Stochastic resonance stimulation might enhance signal detection of sensorimotor signals associated with postural stability. This result has clinical relevance as improvements in postural instabilities associated with FAI might decrease ankle sprain injury.