Postural control is maintained despite a season of sub-concussive head impacts

  • Jill K Dierijck School of Health and Exercise Sciences, University of British Columbia - Okanagan
  • Alexander D Wright School of Health and Exercise Sciences, University of British Columbia - Okanagan
  • Kelsey Bryk MD/PhD Program, University of British Columbia
  • Jonathan D Smirl Souther
  • Michael Jakovac School of Health and Exercise Sciences, University of British Columbia - Okanagan
  • Paul van Donkela School of Health and Exercise Sciences, University of British Columbia - Okanagan

Abstract

Although balance control has been studied extensively following an acute concussion, little is currently known about the influences of multiple sub-concussive head impacts on postural control. Twenty-four elite male football players (age range 18-22) were recruited for the study. Quiet stance data was collected prior to and upon completion of the competitive season. Two one-minute trials with feet hip-width apart and hands-on-hips were performed on a force plate (NDI True Impulse) with A) eyes-open and B) eyes-closed. Biomechanical head-impact exposure was indexed using the xPatch (X2 Biosystems). Centre-of-pressure (COP) metrics included anterior/posterior (AP) and medial/lateral (ML) root-mean-square displacement (RMSd) and mean velocity (COPvel). Biomechanical head-impact exposure data was evaluated for all impacts above 20g. Cumulative peak linear acceleration (PLA) and peak rotational acceleration (PRA) were estimated across the competitive season. RM-ANOVA revealed an effect of condition (eyes-open vs eyes-closed) in AP-RMSd (p=0.035) ML-RMSd (p<0.0001) and ML mean velocity (p<0.0001). However, despite exposure to a cumulative 8147.2 ± 6215.5g in linear acceleration and 34.5x106 ± 59.0x105 rad/s2 in rotational acceleration, there were no significant differences across COP outcomes between pre- and post-season balance metrics. In contrast to the prolonged alterations in quiet stance COP metrics observed following acute concussion, there were no discernable effects of sub-concussive trauma on COP sway in the same population. This is an important finding as it reveals that quiet stance balance is not impaired by one season of participation in contact-sport.