Repetitive subconcussive head impacts and changes in sensory processing for balance control

Background: Repetitive subconcussive head impacts (RHI) may be associated with current and future detrimental neurological effects. However, the effects of RHI on sensory processing for balance control is unknown and may have significant clinical implications if athletes are still participating in sport despite impairments. Research Question: Are there changes in sensory processing for balance control during standing and walking following RHI? Methods: Thirty healthy, adult, amateur soccer players (15 males, 15 females; M=21.8, SD=2.8 years; M=69.9, SD=11.5 kg; M=171.4, SD=8.2 cm) volunteered for the standing balance assessment (i.e., experiment 1). A distinct cohort of twenty healthy, adult, amateur soccer players (10 males, 10 females; M=22.3, SD=4.5 years; M=70.0, SD=10.5 kg; M=170.5, SD=9.8 cm) volunteered for the walking balance assessment (i.e., experiment 2). We used a repeated measures design across three time points (pre-heading, 0-hours post-heading, 24-hours post-heading). Participants were randomly assigned to an experimental (i.e., performed 10 soccer headers in 10 minutes) or a control group (i.e., did not perform any soccer heading between sessions). In experiment 1, participants stood in a virtual reality cave while experiencing simultaneous perturbations to their visual, vestibular, and proprioceptive systems. In experiment 2, participants walked blindfolded along a foam walkway and experienced a vestibular perturbation on the second heel strike of the right foot. Changes in sensory processing were assessed using repeated measures ANOVAs. Results: There were no changes in sensory reweighting during experiment 1 and no changes in balance responses to the vestibular stimulus in experiment 2. Significance: Although the cumulative effects of RHI may result in later-life cognitive, behavioral, and mood impairments, a single episode of repeated soccer headers does not appear to be associated with acute impairments in sensory processing for balance control.