Repetitive head impact exposure and sensory reweighting for upright stance

Abstract

ObjectiveTo compare sensory reweighting between soccer players who report higher exposure to soccer heading and those who report lower exposure to soccer heading.BackgroundExposure to repetitive head impacts (RHI), such as through routine soccer heading, may have potentially detrimental effects.Design/MethodsThirty participants completed a self-reported questionnaire to estimate the number of RHI sustained weekly, and were divided into low-, medium-, and high-RHI groups based on their responses. Sensory reweighting was compared between low-RHI (N = 10, 4 males, 22.9 ± 3.0 years, 170.5 ± 7.7 cm, 70.0 ± 12.14 kg, 2 ± 2 RHI) and high-RHI groups (N = 10, 5 males, 20.0 ± 1.1 years, 170.4 ± 7.4 cm, 69.6 ± 13.4 kg, 60 ± 37 RHI). Participants experienced a visual stimulus at 0.2 Hz, a ±1 mA binaural monopolar galvanic vestibular stimulus (GVS) at 0.36 Hz, and a vibratory stimulus to their bilateral Achilles tendons at 0.28 Hz during standing. The visual stimulus was presented at different amplitudes (0.2, 0.8 m translation in the anterior-posterior direction) to measure the change in leg gain to vision, gain to vibration, and gain to GVS. A repeated-measures ANOVA was used to compare sensory reweighting between groups.ResultsThere were group differences in sensory reweighting for leg gain to GVS (i.e. condition X group effect; F3,54 = 5.068, p = 0.004, η2 = 0.220), whereby the high-RHI group did not reweight gain to GVS across conditions, and gain to vision (F3,54 = 3.397, p = 0.024, η2 = 0.159), whereby the high-RHI group had higher gains than the low-RHI group in the 0.2 m visual stimulus condition. There were no group differences in sensory reweighting for gain to vibration (F1,18 = 0.045, p = 0.834, η2 = 0.003).ConclusionsRoutine soccer heading is associated with relatively high head accelerations. These results suggest that exposure to frequent RHI may induce adaptation that diminishes reliance on vestibular function. Consequently, visual feedback is upweighted to maintain balance during upright stance.