Publications by authors named "Jonathan D Smirl"

Sport-related concussion (SRC) poses a barrier to otherwise health-promoting sport participation. Tackle Football (American Football) is a popular sport with an elevated risk of SRC, which prioritises strength and conditioning. The association between physical performance, notably lower body maximal muscle power and concussion rate, is not well understood in youth tackle football.

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Intimate partner violence (IPV) frequently results in brain injury (IPV-BI) among survivors, with potential long-term effects for both physical and psychological health. This study aimed to examine the impact of chronic IPV-BI on postural control with (eyes open, [EO]) and without (eyes closed, [EC]) visual cues. We hypothesized that more exposure to a history of IPV-BI would be associated with greater postural control disruptions.

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Objectives: Preliminary investigation of exercise and diurnal effects on neurofilament light, glial fibrillary acidic protein, ubiquitin carboxy-terminal hydrolase L1 and total tau.

Methods: Plasma biomarkers were assayed from blood drawn before, during, immediately following, and 1, 2, 4, 6, 8, 24, and 48-h following three exercise conditions completed on a cycle ergometer (control [stationary], moderate intensity interval training and high intensity interval training). Participants with no prior concussion history completed each condition randomized four weeks apart.

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The magnitude of changes in middle cerebral artery mean blood velocity (MCAv) is attenuated when mean arterial pressure (MAP) increases compared with when MAP decreases. This directional sensitivity has been characterized using a time-corrected ratio calculated on MCAv and MAP changes induced by repeated squat-stands (RSS) at 0.05 and 0.

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Alterations in autonomic cardiovascular function may result following mild traumatic brain injury (mTBI), but there is a lack of data evaluating autonomic function in adults with persisting post-concussive symptoms (PPCS). We collected resting measures of heart rate (HR), heart rate variability (HRV), blood pressure (BP) and cardiac baroreceptor sensitivity in 50 adults with PPCS (42.8 (11.

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Dynamic cerebral autoregulation (dCA) reacts differently when mean arterial pressure (MAP) increases versus decreases (i.e., directional sensitivity).

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This investigation explored the impact of partial pressure of end-tidal carbon dioxide (PCO) alterations on temporal neurovascular coupling (NVC) responses across the cardiac cycle and the influence of biological sex via a complex visual scene-search task (""). 10 females and 10 males completed five puzzles, each with 40 seconds of eyes open and 20 seconds of eyes closed, under PCO clamped at ∼40 mmHg (eucapnia), ∼55 mmHg (hypercapnia), and ∼25 mmHg (hypocapnia). Cerebral blood velocity (CBv) in the middle and posterior cerebral arteries (MCAv, PCAv) were measured via Transcranial Doppler ultrasound.

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Background: Although guidelines support aerobic exercise in sub-acute mild traumatic brain injury (mTBI), evidence for adults with persisting post-concussive symptoms (PPCS) after mTBI is lacking. The objective was to evaluate the impact of a sub-symptom threshold aerobic exercise intervention on overall symptom burden and quality of life in adults with PPCS.

Methods: This prospective cohort study was nested within the ACTBI Trial (Aerobic Exercise for treatment of Chronic symptoms following mild Traumatic Brain Injury).

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. The current paper describes the creation of a simultaneous trimodal neuroimaging protocol. The authors detail their methodological design for a subsequent large-scale study, demonstrate the ability to obtain the expected physiologically induced responses across cerebrovascular domains, and describe the pitfalls experienced when developing this approach.

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Background: Little is known regarding long-term consequences (≥5 years) of sport-related concussion (SRC) sustained during adolescence. Adolescent SRC has been linked to athlete considerations of sport participation and subsequent retirement from sport during this critical developmental period. Prolonged SRC symptoms can reduce ability to perform physical activity, and research suggests inactivity can extend years post-injury.

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This study applied alterations in partial pressure of end-tidal carbon dioxide ( ) to challenge dynamic cerebral autoregulation (dCA) responses across the cardiac cycle in both biological sexes. A total of 20 participants (10 females and 10 males; aged 19-34 years) performed 4-min bouts of repeated squat-stand manoeuvres (SSMs) at 0.05 and 0.

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Background: This study explored a novel multimodal neuroimaging approach to assess neurovascular coupling (NVC) in humans using electroencephalography (EEG), functional near-infrared spectroscopy (fNIRS), and transcranial Doppler ultrasound (TCD).

Methods: Fifteen participants (nine females; age 19-32) completed concurrent EEG-fNIRS-TCD imaging during motor (finger tapping) and visual ("Where's Waldo?") tasks, with synchronized monitoring of blood pressure, capnography, and heart rate. fNIRS assessed microvascular oxygenation within the frontal, motor, parietal, and occipital cortices, while the middle and posterior cerebral arteries (MCA/PCA) were insonated using TCD.

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Article Synopsis
  • - This review synthesizes research using multimodal neuroimaging to study the relationship between neuronal activity and blood flow during tasks, emphasizing the importance of neurovascular coupling and accounting for physiological factors.
  • - It includes a comprehensive analysis of 364 studies published before July 31, 2023, focusing on combinations like EEG and fMRI, predominantly during cognitive and visual tasks.
  • - The review highlights that most studies poorly controlled for factors like blood pressure and heart rate, underscoring the need for improved methodology and suggesting further research into sex differences and other physiological influences.
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  • There are different opinions on how high the frequency cut-off point of dynamic cerebral autoregulation (CA) is, with one method suggesting it's around 0.07 Hz and another saying it could be as high as 0.24 Hz.
  • A study looked at how these limits are accurate by having 16 people perform squat-stand exercises at different frequencies while measuring blood flow in their brains.
  • The results showed that while there were some differences between males and females, the overall upper frequency limit for CA was similar regardless of sex, the type of blood vessel, or the heartbeat phase.
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  • Cerebrovascular reactivity (CVR) measures how blood vessels respond to stimuli, with this study focusing on differences during the cardiac cycle rather than just average data.
  • Involving 71 participants, techniques included assessing responses to increased and decreased CO2 levels, revealing that CVR was higher during systole while relative responses varied across diastole and systole.
  • Results indicated that females showed stronger absolute CVR responses, particularly in certain cardiac phases, suggesting that sex-related biological factors may influence these vascular responses.
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Neurovascular coupling (NVC) is the perturbation of cerebral blood flow (CBF) to meet varying metabolic demands induced by various levels of neural activity. NVC may be assessed by Transcranial Doppler ultrasonography (TCD), using task activation protocols, but with significant methodological heterogeneity between studies, hindering cross-study comparisons. Therefore, this review aimed to summarise and compare available methods for TCD-based healthy NVC assessments.

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To examine the feasibility, utility and safety of superimposed lower body negative pressure (LBNP) and tilt during supine cycling in individuals suffering from persisting post-concussive symptoms (PPCS). Eleven individuals aged 17-31 (6 females/5 males) participated in two randomized separate visits, 1 week apart. A ramp-incremental test was performed during both visits until volitional failure.

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Cerebral hemodynamics have been quantified during exercise via transcranial Doppler ultrasound, as it has high-sensitivity to movement artifacts and displays temporal superiority. Currently, limited research exists regarding how different exercise modalities and postural changes impact the cerebrovasculature across the cardiac cycle. Ten participants (4 females and 6 males) ages 20-29 completed three exercise tests (treadmill, supine, and upright cycling) to volitional fatigue.

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Introduction: Concussion is known to cause transient autonomic and cerebrovascular dysregulation that generally recovers; however, few studies have focused on individuals with an extensive concussion history.

Method: The case was a 26-year-old male with a history of 10 concussions, diagnosed for bipolar type II disorder, mild attention-deficit hyperactivity disorder, and a history of migraines/headaches. The case was medicated with Valproic Acid and Escitalopram.

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Frequency-domain near-infrared spectroscopy (FD-NIRS) has been used for non-invasive assessment of cortical oxygenation since the late 1990s. However, there is limited research demonstrating clinical validity and general reproducibility. To address this limitation, recording duration for adequate validity and within- and between-day reproducibility of prefrontal cortical oxygenation was evaluated.

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Numerous driven techniques have been utilized to assess dynamic cerebral autoregulation (dCA) in healthy and clinical populations. The current review aimed to amalgamate this literature and provide recommendations to create greater standardization for future research. The PubMed database was searched with inclusion criteria consisting of original research articles using driven dCA assessments in humans.

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A directional sensitivity of the cerebral pressure-flow relationship has been described using repeated squat-stands. Oscillatory lower body negative pressure (OLBNP) is a reproducible method to characterize dynamic cerebral autoregulation (dCA). It could represent a safer method to examine the directional sensitivity of the cerebral pressure-flow relationship within clinical populations and/or during pharmaceutical administration.

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Wearable technology and neuroimaging equipment using photoplethysmography (PPG) have become increasingly popularized in recent years. Several investigations deriving pulse rate variability (PRV) from PPG have demonstrated that a slight bias exists compared to concurrent heart rate variability (HRV) estimates. PPG devices commonly sample at ~20-100 Hz, where the minimum sampling frequency to derive valid PRV metrics is unknown.

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