Objective To examine how sub-concussive head trauma throughout a contact-sport season affects quiet stance centre of pressure (COP) sway

Design Prospective cohort

Setting Laboratory

Participants: Twenty-four elite male football players (age range 18–22) were recruited for the study

Intervention Quiet stance data was collected at the start and at the end of the competitive season. One-minute trials were performed with eyes-open and eyes-closed on a force plate (NDI True Impulse) with feet hip-width apart and hands-on-hips. Biomechanical head-impact exposure was indexed using the xPatch (X2 Biosystems)

Outcome measures COP measures: Anterior/posterior (AP) and medial/lateral (ML) root-mean-square displacement (RMSd) and mean velocity. Biomechanical head-impact data: For hits above 20g, peak linear acceleration (PLA), and peak rotational acceleration (PRAwere estimated across the competitive season. Independent variables included time (2) and condition (2)

Results RM-ANOVA reveal an effect of condition (eyes-open vs eyes-closed) in AP-RMSd (p=0.035, 95% CI: 0.006, 0.159), ML-RMSd (p<0.0001, CI: 0.083, 0.250), and ML mean velocity (p<0.0001, 95% CI: 0.111, 0.308). However, despite exposure to a cumulative 8147.2±6215.5 g in linear acceleration and 34.5 x 106 ± 59.0x106 rad/s2 in rotational acceleration, there were no significant differences between conditions for COP measures at post-season

Conclusions In contrast to the prolonged COP alterations observed following acute concussions, there were no discernable effects of sub-concussive trauma on COP sway during quiet stance in the same population. This is an important finding as it reveals that participation in contract-sport does not impair quiet stance balance

Competing interests None.