Decreased Anticipatory Postural Adjustments During Gait Initiation Acutely Postconcussion

Abstract

Objective The purpose of this study was to investigate anticipatory postural adjustments (APA) during the transitional movement task of gait initiation (GI) in individuals acutely following a concussion. Design Cohort Study. Setting University Research Center. Participants A population based sample of 84 participants divided into two equal groups of acutely post-concussion (CONC) and healthy student athletes. Intervention Participants were tested on two occasions – a pre-injury baseline test and then the CONC group was retested acutely post-concussion and the control group again at a similar time. All participants completed 5 trials of GI on 4 forceplates. Main Outcome Measures The dependent variables were the displacement and velocity of the center of pressure (COP) during the APA phase and initial step kinematics. Comparisons were made with a 2 (Group) × 2 (Time) repeated measures ANOVA. Results There was a significant interaction for COP posterior displacement (P<0.001) and lateral displacement (P<0.001). Posteriorly, post-hoc testing identified a significant reduction in CONC (PRE: 5.7 ± 1.6 cm and POST: 2.6 ± 2.1 cm, P<0.001), but no difference in Control (PRE: 4.0 ± 1.6 cm and POST: 4.0 ± 2.5 cm, P=0.921). Laterally, post-hoc testing identified a significant reduction in CONC (PRE: 5.8 ± 2.1 cm and POST: 3.8 ± 1.8 cm, P<0.001), but no difference in Control (PRE: 5.0 ± 2.5 cm and POST: 5.2 ± 2.4 cm, P=0.485). Conclusions The results of this study suggest difficulty in the planning and execution of GI acutely post-concussion and posterior APA displacement and velocity are highly effective measures of impaired postural control. Finally, the APA phase is linked to the supplementary motor area which suggests a supraspinal contribution to post-concussion impaired postural control.

Clinical Assessments of Balance in Adults with Concussion: An Update

“…Individuals with concussion injury commonly have a reduction in the displacement and overall velocity of the CoP in both directions, reflecting a reduction in anticipatory postural control. 43 The anticipatory adjustment phase is controlled via higher level cortical processing and reductions in this pattern is consistent with other neurological disorders such as Parkinson's disease. [35][36][37][38] These reductions in both the CoP displacement and velocity indicate a more conservative stepping pattern where the brain actively constrains the postural system (reduction of the total degrees of freedom) as a protective mechanism against falls.…”

“…Gait is a stable motor task in adults and it routinely identifies postural control impairments across neurological populations. [35][36][37][38] However, gait evaluation postconcussion may require additional challenges such as the presence of a dual task [39][40][41][42] or during anticipatory postural control 7,43 for apparent issues to be observable postconcussion.…”

“…With an additional dual task to load cortical resources, acute and lingering postural control deficits have a greater potential to be identified. 7,39,40,43 Impairments in gait initiation are commonly observed as a reduction of the CoP displacement and velocity in both mediolateral and AP directions as the movement of stepping is initiated during the anticipatory adjustment phase. After movement initiation, the CoP translates posteriorly and laterally toward the initial swing limb (anticipatory adjustment phase).…”

Repetitive Head Impacts in Football Do Not Impair Dynamic Postural Control

“…The displacement of the center of pressure (COP) was divided into three segments based on two landmarks as frequently described in the literature. (23, 39) (Figure 2A) Briefly, the COP initially is displaced posteriorly and towards the initial swing limb and this represents the anticipatory postural adjustment (APA) component of GI. Thereafter, the transitional phase occurs as the COP shifted from the initial swing limb to the stance limb as the swing limb unloads.…”

“…The anterior/posterior (AP) and medial-lateral (ML) displacement was calculated for each of the three phases. (23, 39)…”