Kelsey M. Evans

Evidence of a conservative gait strategy in athletes with a history of concussions

Background A history of 3 or more concussions is frequently associated with numerous short- and long-term neuropathologies. Impairments in postural control are a known acute consequence of concussion; however, limited evidence exists on the effects of multiple concussions on gait. The purpose of this study was to assess gait stepping characteristics in collegiate aged student-athletes based on concussion history. Methods There were 63 participants divided into 3 even groups based on concussion history: ≥3 concussions, 1–2 concussions, and 0 concussion. All participants completed 10 trials of gait on a 4.9 m instrumented walkway. The dependent variables of interest included both gait stepping characteristics (step velocity, length, and width, double support time, and the percentage of the gait cycle in stance) and coefficient of variability (CoV) measures (step length, time, and width). The gait stepping characteristics were compared first with a MANOVA with follow-up 1-way ANOVAs and Tukey post hoc tests as appropriate. The CoV measures were compared with 1-way ANOVAs and Tukey post hoc tests. Results There were main effects for group for step velocity, length, width, and double support time. Overall, the 0 concussion group displayed typical healthy young gait parameters and performed significantly better than either concussion group. The 0 concussion group had a significantly greater step length CoV, but there were no differences in the step time or width CoV. Conclusion This finding provides evidence of subtle impairments in postural control during gait among individuals with prior history of concussion which could be an early indicator of future neurological deficiencies. The limited difference in the variability measures is consistent with prior static stance studies and could suggest the individuals constrain their motor systems to reduce variability. Taken together, these findings suggest a conservative gait strategy which is adopted by individuals with a history of concussions.

Altered dynamic postural control during gait termination following concussion

Impaired postural control is a cardinal symptom following concussion. Planned gait termination (GT) is a non-novel, dynamic task that challenges postural control in individuals with neurological deficits, and it could be an impactful measure for identifying dynamic postural control impairments following concussion. Therefore, the purpose of this study was to assess acute post-concussion dynamic postural control utilizing a planned GT task. The concussion participants (n=19, age: 19.0±0.8years, height: 177.0±10.1cm, weight: 83.3±20.0kg) completed five planned GT trials during preseason baseline testing (Baseline) and on Day 1 post-concussion (Day-1). Healthy control participants (n=19, age: 20.4±1.2years, height: 173.8±8.9cm, weight: 80.2±17.6kg) completed the same trials a week apart. The dependent variables of interest included COP displacement and velocity in the mediolateral (ML) and anteroposterior (AP) axes during the three phases (braking, transitional, stabilization) of planned GT. There were significant interactions observed in both the braking ML and transitional AP displacement (p=0.042, p=0.030) and velocity (p=0.027, p=0.030). These results suggest a conservative post-concussion motor control strategy during planned GT. Further, these results support the use of dynamic postural control tasks as measures of post-concussion impairments.

Sport-Related Concussion Induces Transient Cardiovascular Autonomic Dysfunction

Recent evidence suggests that concussions may disrupt autonomic cardiovascular control. This study investigated the initial effects of concussion on cardiovascular function using three autonomic reflex tests. Twenty-three recreational athletes (12 women, 11 men) were divided into concussed (n = 12) and control (n = 11) groups. Concussed participants performed forced breathing, standing, and Valsalva autonomic tests four times: 1) within 48 h of injury; 2) 24 h later; 3) 1 wk after injury; and 4) 2 wk after injury. The controls performed the same tests on the same schedule. Differences in heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) responses to the tests were continuously measured using finger photoplethysmography and were analyzed using repeated-measures multivariate ANOVAs and ANOVAs. Within 48 h of injury, the concussed group had significantly greater resting SBP (t21 = 2.44, P = 0.02, d = 1.03), HR (t21 = 2.33, P = 0.03, d = 1.01), and SBP responses to standing (t21 = 2.98, P = 0.01, d = 1.24), and 90% SBP normalization times (t21 = 2.64, P = 0.02, d = 1.10) after the Valsalva, but those group differences subsided 24 h later. There was also a significant interaction with the HR responses to forced breathing (F3,60 = 4.13, P = 0.01, ηp2 = 0.17), indicating the concussed responses declined relative to the controls over time. The results demonstrate that concussion disrupted autonomic cardiovascular control, and that autonomic reflex tests are practical means by which to evaluate that dysfunction.

Relationship between Information Processing and Postural Stability in Collegiate Division I NCAA Athletes: Does Concussion History Matter?

Background: Concussions have been associated with deficits in balance and postural stability. Subjects sustaining mild to moderate head injuries showed an increase in inhibition of the primary motor cortex which has been associated with sensorimotor organization and movement execution changes. Purpose: The purpose of this study was to examine the relationship between postural stability and information processing in collegiate athletes with and without a history of concussion. Methods: One-hundred and sixty-five Division I student-athletes completed balance and neurocognitive baseline testing. Thirty-four had a previous history of concussion. Postural sway and spatio-temporal characteristics of center of pressure were measured under four conditions: eyes open firm surface, eyes closed firm surface, eyes open foam surface, eyes closed foam surface. Information processing data came from two composite scores from a neurocognitive assessment tool and from a somatosensory stimulation test. Results: Results showed that student-athletes with a history of concussions, although healthy at the time of testing, had differences in postural control compared to student-athletes without a history of concussion. While sway index scores were not significantly different, spatio-temporal measures showed larger displacements in CoP in previously concussed student-athletes. Reaction times and visual motor speeds were significantly correlated with sway index scores suggesting that processing time does influence balance control in all participants. Conclusion: Sustained balance control differences in previously concussed student-athletes may have implications for compensation strategies and risk of additional injuries.

Decreased Anticipatory Postural Adjustments During Gait Initiation Acutely Postconcussion

OBJECTIVE To investigate anticipatory postural adjustments (APAs) during the transitional movement task of gait initiation (GI) in individuals acutely after a concussion. DESIGN Cohort study. SETTING University research center. PARTICIPANTS A population-based sample of participants (N=84) divided into 2 equal groups of acutely postconcussion and healthy student athletes. INTERVENTION Participants were tested on 2 occasions: a preinjury baseline test and then the concussion group was retested acutely postconcussion and the healthy student athlete 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 analysis of variance. RESULTS There was a significant interaction for COP posterior displacement (P<.001) and lateral displacement (P<.001). Posteriorly, post hoc testing identified a significant reduction in the concussion group (pretest: 5.7±1.6cm; posttest: 2.6±2.1cm; P<.001), but no difference in the healthy student athlete group (pretest: 4.0±1.6cm; posttest: 4.0±2.5cm; P=.921). Laterally, post hoc testing identified a significant reduction in the concussion group (pretest: 5.8±2.1cm; posttest: 3.8±1.8cm; P<.001), but no difference in the healthy student athlete group (pretest: 5.0±2.5cm; posttest: 5.2±2.4cm; P=.485). CONCLUSIONS The results of this study suggest difficulty in the planning and execution of GI acutely postconcussion, 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 postconcussion impaired postural control.

Virtually transforming detect: moving a 2-D gamified health assessment to virtual reality

Researchers from Georgia Tech, Emory University, and Georgia Tech Research Institute previously collaborated on a 2D Heads-Up Display based gamified health assessment focused on determining neurologic impairment. As a part of continuing gamification of the assessment, the entire project was translated to 3D Virtual Reality under significant constraints. The system needed to test the same neural pathways in the same manner as the previous assessment in order to use data from the 2D system as validation for the approach. Some aspects of user response to immersion required significant changes to gameplay mechanics. Iterative, collaborative development was critical to increasing gamification while maintaining an effective assessment tool.