Greater exposure to repetitive subconcussive head impacts is associated with vestibular dysfunction and balance impairments during walking

Abstract

Exposure to repetitive subconcussive head impacts (RSHI), specifically soccer heading, is associated with white matter microstructural changes and cognitive performance impairments. However, the effect of soccer heading exposure on vestibular processing and balance control during walking has not been studied. Galvanic vestibular stimulation (GVS) is a tool that can be used to probe the vestibular system during standing and walking. The purpose of this study was to investigate the association of soccer heading with subclinical balance deficits during walking. Twenty adult amateur soccer players (10 males and 10 females, 22.3 ± 4.5 years, 170.5 ± 9.8 cm, 70.0 ± 10.5 kg) walked along a foam walkway with the eyes closed under 2 conditions: with GVS (∼40 trials) and without GVS (∼40 trials). Outcome measures included mediolateral center-of-mass (COM), center-of-pressure (COP) separation, foot placement, mediolateral ankle modulation, hip adduction, and ankle push off. For each balance mechanism, a GVS response was calculated (GVS, mean [without GVS]). In addition, participants completed a questionnaire, reporting soccer heading exposure over the past year. A linear regression model was used to determine if vestibular processing and balance during walking were related to RSHI exposure. Both foot placement (R2 = 0.324, p = 0.009) and hip adduction (R2 = 0.183, p = 0.50) were predicted by RSHI; whereby, greater exposure to RSHI was associated with greater foot placement and hip adduction responses. However, COM-COP separation (R2 < 0.001, p = 0.927), ankle modulation (R2 = 0.037, p = 0.417), and push off (R2 < 0.001, p = 0.968) were not related to RSHI exposure. Individuals who were exposed to greater RSHI were more perturbed by vestibular stimulation during walking, suggesting that there may be vestibular dysfunction and balance impairments with frequent heading; specifically, individuals with greater exposure to RSHI responded with larger foot placement and hip adduction responses to GVS.