Sensory reweighting for upright stance in soccer players: A comparison of high and low exposure to soccer heading.

The purpose of this study was to compare sensory reweighting for upright stance between soccer players who report higher soccer heading exposure to those who report lower soccer heading exposure. Thirty participants completed a self-reported questionnaire to estimate the number of soccer headers experienced over the prior year and were divided into "low exposure" and "high exposure" groups based on their responses. Sensory reweighting for upright stance was assessed by simultaneously perturbing visual, vestibular, and proprioceptive systems. The visual stimulus was a sinuosoidal translation of the visual scene at 0.2Hz, the vestibular stimulus was ±1mA binaural monopolar galvanic vestibular stimulation (GVS) at 0.36Hz, and the proprioceptive stimulus was Achilles tendon vibration at 0.28Hz. The visual stimulus was presented at two amplitudes (0.2m, 0.8m). Center of mass (COM) gain/phase to each modality, total power, 95% area and velocity were compared between "low exposure" (N=15, 6 males, 21.5±1.9years, 27.7±31.6headers) and "high exposure" groups (N=15, 10 males, 22.1±3.5years, 734.9±877.7headers). Without vibration, COM 95% area (F=5.861, p=.022*, partial η²=.173), velocity (F=14.198, p=.001, partial η²=.336), and total power (F=13.491, p=.001, partial η²=.325) for the "high exposure" group were higher than for the "low exposure" group and postural sway lagged the vestibular stimulus in the "high exposure" group rather than leading it as in the "low exposure" group (F=4.765, p=.038, partial η²=.145). There were no differences in sensory reweighting and no differences in COM gain/phase between groups. These findings lend empirical evidence to a detrimental effect of soccer heading exposure on balance control during upright stance.