Abstract:
Context: Following a concussion, athletes are at higher risk for another concussion and musculoskeletal injuries. Altered perception of action boundaries, or the limits of one’s action capabilities, is one possible mechanism for this increase in injury risk following concussion. Objective: To evaluate differences in physical and emotional symptoms, neurocognitive performance, and action boundary behavior between subjects with no concussion history (NoHx) and concussion history (ConcHX). Design: Cross-sectional Setting: Research laboratory Patients or Other Participants: ConcHx (n = 22; age: 21.8 ± 3.0 years, height: 174.0 ± 8.3 cm, mass: 77.8 ± 14.8 kg) and NoHx athletes (n = 24; age: 21.6 ± 2.0 years, height: 176.0 ± 10.0 cm, mass: 72.0 ± 15.3 kg) participated. Interventions: Participants completed the Patient Health Questionnaire-9 (PHQ-9), General Anxiety Disorder-7 (GAD-7), Vestibular-Ocular Motor Screen (VOMS), Immediate PostConcussion Assessment and Cognitive Testing (ImPACT), Post-Concussion Symptom Score (PCSS) and the Perception Action Coupling Task (PACT). The PACT presents pairs of ‘virtual’ balls and holes of differing sizes, to assess the ability to accurately and quickly determine if a ball will fit inside a hole on an iPad. Eight “ballto-hole” aperture ratios are presented from 0.2 (ball is much smaller than the hole) to 1.8 (hole is much smaller than the ball). Main Outcome Measures: The PHQ-9 measures depression, the GAD-7 measures anxiety, VOMS assesses vestibular/oculomotor symptoms and impairment, and ImPACT assesses cognitive performance, which includes the PCSS to assess total symptom severity. Reaction time (period from stimulus presentation to removing finger from home button), movement time (period between home button finger removal and placing finger on the joystick), initiation time (period between finger touching the joystick and moving in the intended direction), and accuracy percentage are the PACT outcomes. Appropriate parametric/nonparametric independent-samples tests were used to assess significant differences (p < 0.05, a priori). Results: ConcHx reported 2.7 ± 1.5 previous concussions and 263.8 ± 228.9 days since last concussion at time of testing. ConcHx reported higher symptom severity (ConcHx: 12.1 ± 14.0, NoHx: 3.7 ± 5.2; p = 0.013), depression (ConcHx: 4.2 ± 4.2, NoHx: 1.4 ± 1.7; p < 0.001) and anxiety (ConcHx: 3.7 ± 3.9, NoHx: 1.7 ± 2.2; p = 0.03) scores than NoHx. ConcHx also reported more symptoms in response to vertical saccades (ConcHx: 0.9 ± 1.7, NoHx: 0.2 ± 0.4; p = 0.048), vertical vestibular-ocular reflex (ConcHx: 0.9 ± 1.2, NoHx: 0.2 ± 0.4; p = 0.019), and visual motion sensitivity (ConcHx: 1.1 ± 1.5, NoHx: 0.2 ± 0.5; p = 0.013). Average PACT movement time (ConcHx: 0.32 ± 0.10 msecs, NoHx: 0.25 ± 0.07 msecs; p = 0.02) and reaction time (ConcHx: 0.13 ± 0.03 msecs, NoHx: 0.11 ± 0.01 msecs; p = 0.01) were longer in ConcHx, while ConcHx were also less accurate at aperture ratios 0.4 (-2.6%), 0.6 (-2.7%) and 0.8 (-5.6%). No differences were observed on ImPACT. Conclusions: This study indicates that athletes with previous concussion experience impaired action boundary perception. However, further study is needed to determine cause and effect in this population. If dysregulated action boundary perception is confirmed as a concussion consequence, it could be a viable mechanism for increased musculoskeletal injury risk following concussion and inform subsequent treatments strategies to mitigate injury risk following concussion.