Date of Award

Spring 2026

Document Type

Open Access Dissertation

Department

Exercise Science

First Advisor

Robert Davis Moore

Abstract

Concussions, or mild traumatic brain injuries, are common amongst adolescent populations. Despite the qualifier of “mild”, these injuries can have a lasting impact on quality of life and school function. It has long been suggested that females experience poorer outcomes following concussion compared to their male counterparts, yet much research focuses primarily on male populations. Various theories have been proposed to explain these reported sex differences in concussion outcomes, ranging from socio-cultural differences in symptom reporting to neuroanatomical differences and the influence of sex hormones. Cardiac autonomic function (C-ANS) has emerged as a potential contributing mechanism to post-concussive symptoms. Although C-ANS function is known to differ between males and females in healthy populations, our understanding of how this may present following concussion remains incomplete.

The C-ANS plays an important role in regulating cardiovascular adaptations to changing situational demands, such as during exercise and physical exertion. As such, the purpose of the present work was to examine sex differences in C-ANS function during conditions involving varying levels of physical exertion in adolescents recently incurring a concussion. To investigate the potential contribution of the C-ANS to sex differences in concussion, these studies also examined the differential association between C-ANS function and concussion symptoms in males and females. Study 1 investigated sex differences in heart rate recovery following acute submaximal aerobic exercise. Results revealed that females achieved a lower percentage change in heart rate than males, but did not differ from males on recovery of heart rate over time. Exercise-related variables were also unrelated to post-exercise clinical measures for males and females.

Study 2 was a longitudinal study of heart rate variability (HRV) evaluated during rest, deep breathing, and isometric handgrip contraction. The secondary aim of this study was to evaluate the influence of menstrual cycle phase at time of concussion on such outcomes. There were no sex differences in HRV recovery over time; however, females with a recent concussion displayed lower HRV during handgrip than males, regardless of time. Males and females also displayed different relationships between HRV and clinical measures. In male participants, HRV was associated with both self-reported symptoms and cognitive task performance, but in female adolescents, HRV was only associated with cognitive task performance. Additionally, females who were injured during the luteal phase of their menstrual cycle displayed lower HRV coherence during deep breathing compared to those injured during the follicular phase and males. The present work highlights the need to consider sex as a moderating variable when assessing C-ANS function following concussion. These results can have important implications when administering interventions with a basis in C-ANS function, such as aerobic exercise or HRV biofeedback.

Rights

© 2026, Kiersten Isabella Mangold

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