Analysis of Free-Living Mobility in People with Mild Traumatic Brain Injury and Healthy Controls: Quality over Quantity.

Balance and mobility issues are common non-resolving symptoms following mild traumatic brain injury (mTBI). Current approaches for evaluating balance and mobility following an mTBI can be subjective and suboptimal as they may not be sensitive to subtle deficits, particularly in those with chronic mTBI. Wearable inertial measurement units (IMU) allow objective quantification of continuous mobility outcomes in natural free-living environments. This study aimed to explore free-living mobility (physical activity and turning) of healthy and chronic mild traumatic brain injury (mTBI) participants using a single IMU. Free-living mobility was examined in 23 healthy control (48.56 ± 23.07 years) and 29 symptomatic mTBI (40.2 ± 12.1 years) participants (average 419 days post-injury, persistent balance complaints) over 1 week, using a single IMU placed at the waist. Free-living mobility was characterized in terms of macro (physical activity volume, pattern and variability) and micro-level (discrete measures of turning) features. Macro-level outcomes showed those with chronic mTBI had similar quantities of mobility compared with controls. Micro-level outcomes within walking bouts showed that chronic mTBI participants had impaired quality of mobility. Specifically, people with chronic mTBI made larger turns, had longer turning durations, slower average and peak velocities (all