2026 Theses Doctoral

Effects of Aerobic Exercise on Executive Function and Autonomic Regulation in Children with Attention Deficit Hyperactivity Disorder: A Systematic Review and Experimental Investigation of Acute Exercise Dose and Mechanisms

Khodaverdi, Zeinab

Attention-Deficit/Hyperactivity Disorder (ADHD) is a common neurodevelopmental condition marked by chronic inattention, hyperactivity, and impulsivity, and it is frequently accompanied by executive function (difficulties in domains such as working memory, inhibitory control, and cognitive flexibility. Pharmacological and psychosocial treatments are helpful but not sufficient for many children, motivating interest in low-risk, scalable adjuncts that support self-regulation in daily life. Aerobic exercise (AE) is a promising candidate, yet current guidance for children with ADHD is limited by inconsistent specification of acute and chronic exercise “doses” (intensity, duration, frequency), sparse attention to when executive function is tested after exercise, and limited mechanistic work on autonomic regulation. Cardiac vagal control, indexed by heart rate variability (HRV), has been proposed as a peripheral marker of neurovisceral integration that may link exercise-induced shifts in autonomic state to executive function.

This dissertation examined whether AE can be used in a more targeted way to support executive function in children with ADHD and whether cardiac vagal regulation plays a meaningful role in this process. It combines one systematic review and two small mechanistic crossover trials. The systematic review synthesized acute and chronic AE interventions with executive function outcomes in youth with ADHD, organizing findings by intensity, duration, frequency, and post-exercise executive function testing window. Across heterogeneous protocols, 20–30 minute bouts of moderate-to-vigorous AE were most often associated with small-to-moderate, short-term improvements in inhibitory control when executive function was assessed within the first half hour after exercise, while chronic programs tended to yield broader, more consistent gains in executive function and ADHD symptom ratings, albeit with substantial variability in methods and reporting.

Chapters 3 and 4 report a randomized, within-participant crossover study in which ten children aged 8–11 years with ADHD completed three 20-minute treadmill sessions at light (30–40% VO₂Reserve), moderate (50–60% VO₂Reserve), and vigorous (70–80% VO₂Reserve) intensities prescribed from cardiopulmonary exercise testing and verified via continuous heart-rate monitoring. Executive function (Flanker, Dimensional Change Card Sort, and List Sorting Working Memory from the NIH Toolbox) was assessed immediately and 30 minutes post-exercise. Linear mixed-effects models with pre-specified contrasts indicated that, within this pilot sample, no single intensity produced reliably superior short-term executive function performance once multiplicity was controlled; confidence intervals were wide, constraining only large intensity differences and leaving smaller effects unresolved.

In a parallel analysis, continuous R–R interval recordings from a Polar H10 chest strap heart rate monitor were used to derive short-term HRV segments immediately before and during executive function tasks, focusing on pre-task lnRMSSD (the natural-log–transformed root mean square of successive differences) and task-evoked vagal withdrawal as candidate mechanistic markers. Within the same crossover framework, pre-task lnRMSSD was consistently lower when executive function was assessed immediately post-exercise than when assessed 30 minutes post-exercise, indicating a timing-related difference in starting autonomic state. In contrast, task-onset vagal withdrawal (on-task lnRMSSD adjusted for pre-task lnRMSSD) did not show reliable condition-specific differences across intensities or executive function testing windows, suggesting that exercise-related modulation of task-evoked lnRMSSD was limited in this mechanistic pilot.

Taken together, the three studies support AE as a feasible, low-risk adjunctive strategy for children with ADHD, while challenging overly simple claims about a single “best” acute intensity or a single dominant autonomic mechanism. Rather than prescribing a narrow target, the findings point toward prioritizing achievable, heart rate-guided moderate-to-vigorous activity, allowing flexibility in scheduling executive function-demanding tasks during early post-exercise recovery, and pursuing larger, better-powered trials that integrate richer time courses, multi-level mechanistic measures (e.g., HRV and neural indices), and person-level moderators such as fitness and medication status.