Understanding Balance Control in Response to Gait Perturbations in Adults with Attention Deficit Hyperactivity Disorder

Individuals with attention deficit hyperactivity disorder (ADHD) are at higher risk of injury compared to neurotypical individuals. Additionally, children with ADHD become injured from falls with more frequency and severity, which may be an indication of balance dysfunction. Gait and standing studies done in children and adults with ADHD found higher variability in baseline walking parameters in children, as well as deficits in balance responses to perturbations and greater postural instability in children and adults. Additionally, this postural instability is associated with higher levels of regional cerebellar grey matter volume, and low neurotransmitter dopamine. There are currently no studies investigating balance during gait in adults with ADHD, even though falls frequently occur during walking within this group. The purpose of the current study was to understand the effects of ADHD on balance control in adults to inform the direction of future research. The aim was to investigate differences in balance responses between individuals with ADHD and those without during unexpected gait perturbations. It was hypothesized that adults with ADHD will exhibit impaired balance control, longer onset latency and greater muscle activation in comparison to control (non-ADHD). To test the hypotheses, twenty-two (22) participants (12 ADHD, 10 non-ADHD) were instructed to walk across an 8-meter walkway for 24 walking trials, 12 of which contained unexpected uneven walking surface perturbations in one of four directions (medial, lateral, anterior, posterior). The other 12 trials included random/no perturbations and were interspersed between to ensure unpredictability. Center of mass (COM), lateral base of support (BOS) and center of pressure (COP) was measured using force plate and kinematic data. Surface electromyography (EMG) was taken for four muscles of each leg (tibialis anterior, medial gastrocnemius, rectus femoris and medial hamstrings). The Adult ADHD Self Report Scale (ASRSv1.1) was also used to record ADHD symptom severity. Results showed that the ADHD group had a significantly higher COM-COP separation maximum in the anteroposterior direction (AP), a higher COM-BOS range, and a lower COM-BOS maximum and minimum in comparison to controls. There were no differences in the EMG measurements. This indicates adults with ADHD do exhibit balance deficits in comparison to adults without ADHD during both steady-state overground walking and in response to perturbations. Participants with ADHD also had more conservative balance responses when they encountered perturbations with greater threats to balance. In summary, this study demonstrates that ADHD is associated with balance control deficits in adults and provides insight on specific differences in stability during walking perturbations. These are findings that can be used to inform further areas of research in the topic.