Sub-concussive trauma, acute concussion, and history of multiple concussions: Effects on quiet stance postural control stability

Although balance control has been studied extensively following acute concussion, little is known regarding repetitive sub-concussive head impacts or chronic exposure to multiple concussive events. Quiet stance postural control was characterized in contact sport athletes at pre-season (n = 135) and post-season (n = 48) to evaluate the effects of subconcussive trauma to the head. To determine the impact of acute concussion on postural control, athletes diagnosed with a concussion during the season (n = 12) were tested at 72-h, 2-weeks, and 1 month post-injury. Because only 4 of the concussed athletes completed baseline testing, control athletes (n = 12) matched for sport, age, body mass index (BMI), and previous concussion history served as a comparison group. Finally, the effects of previous concussion history on quiet stance postural control were determined by comparing pre-season data in contact sport athletes with either zero (Hx(0), n = 50) or three or more (Hx(3+), n = 25) previous concussions. A force plate was used to compare changes in centre-of-pressure root-mean-square displacement (RMSdisp) and mean-velocity (COPvel) in the anterior/posterior (AP) and medial/lateral (ML) directions. One-minute trials were performed with feet hip-width apart, hands-on-hips, and A) eyes-open and B) eyes-closed. Biomechanical head-impact exposure (impacts over 10 g) was indexed over the season using mastoid-fixed impact sensors. In acutely injured athletes, repeated-measures ANOVA revealed a significant effect of time for RMSdisp AP with increased displacement at 2 weeks compared to 72 h (p = 0.008, 95% CI:-0.180, -0.310 cm). No other COP variables were affected by acute concussion. Moreover, there was no effect of concussion history or repeated sub-concussive impacts on any quiet stance metric. Additionally, head-impact exposure metrics were not correlated with COP metrics. Taken together, the data suggests alterations in COP sway during quiet stance persist in the acute 2-week period after injury. These findings were not present with either a history of multiple concussions or exposure to sub-concussive head impacts indicating acute concussion does not have appear to have long term effects for these measures.