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Background: Vestibular deficit is common following concussion and may affect gait. The purpose of this study was to investigate differences in head and pelvic center of mass (COM) movement during gait in military tactical athletes with and without concussion-related central vestibular impairment.Material and Methods: 24 patients with post-concussion vestibular impairment (20 males, 4 females; age: 31.7 ± 7.9 years; BMI: 27.3 ± 3.3) and 24 matched controls (20 males, 4 females; age: 31.8 ± 6.4 years; BMI: 27.2 ± 2.6) were included in the analyses. Three-dimensional head and pelvic displacement and velocities were collected at a 1.0 m/s standardized treadmill walking speed and assessed using Statistical Parametric Mapping t-tests. Maximum differences (dmax) between groups were reported for all significant kinematic findings.Results: The Vestibular group demonstrated significantly diminished anteroposterior head excursions (dmax = 2.3 cm, p = 0.02) and slower anteroposterior (dmax = 0.37 m/s, p = 0.01), mediolateral (dmax = 0.47 m/s, p = 0.02) and vertical (dmax = 0.26 m/s, p < 0.001) velocities during terminal stance into pre-swing phases compared to the Control group. Vertical pelvic excursion was significantly increased in midstance (dmax = 2.4 cm, p = 0.03) and mediolaterally during pre- to initial-swing phases (dmax = 7.5 cm, p < 0.001) in the Vestibular group. In addition, pelvic velocities of the Vestibular group were higher mediolaterally during midstance (dmax = 0.19 m/s, p = 0.02) and vertically during post-initial contact (dmax = 0.14 m/s, p < 0.001) and pre-swing (dmax = 0.16 m/s, p < 0.001) compared to the Control group.Significance: The Vestibular group demonstrated a more constrained head movement strategy during gait compared with Controls, a finding that is likely attributed to a neurological impairment of visual-vestibular-somatosensory integration.

We have previously identified three balance mechanisms that young healthy adults use to maintain balance while walking. The three mechanisms are: 1) The lateral ankle mechanism, an active modulation of ankle inversion/eversion in stance; 2) The foot placement mechanism, an active shift of the swing foot placement; and 3) The push-off mechanism, an active modulation of the ankle plantarflexion angle during double stance. Here we seek to determine whether there are changes in neural control of balance when walking at different cadences and speeds. Twenty-one healthy young adults walked on a self-paced treadmill while immersed in a 3D virtual reality cave, and periodically received balance perturbations (bipolar galvanic vestibular stimulation) eliciting a perceived fall to the side. Subjects were instructed to match two cadences specified by a metronome, 110bpm (High) and 80bpm (Low), which led to faster and slower gait speeds, respectively. The results indicate that subjects altered the use of the balance mechanisms at different cadences. The lateral ankle mechanism was used more in the Low condition, while the foot placement mechanism was used more in the High condition. There was no difference in the use of the push-off mechanism between cadence conditions. These results suggest that neural control of balance is altered when gait characteristics such as cadence change, suggesting a flexible balance response that is sensitive to the constraints of the gait cycle. We speculate that the use of the balance mechanisms may be a factor resulting in well-known characteristics of gait in populations with compromised balance control, such as slower gait speed in older adults or higher cadence in people with Parkinson’s disease.