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Purpose: Symptom scores commonly measured following concussion were compared between male and female adolescents with (Hx+) and without (Hx−) a history of concussion, pre and post physical exertion testing. Methods: Eighty (males [n = 60; Hx+ = 19], female [n = 20; Hx+ = 5]) high school students (ages 15–17 y) completed the Buffalo Concussion Treadmill Test once and the modified shuttle run test twice. Symptom scores were collected using the 22-point Symptom Evaluation Scale on the Sport Concussion Assessment Tool (version 5) immediately pre and post physical exertion testing. Results: The symptoms most reported during preexertional testing were fatigue/low energy, feeling slowed down, and nervous/anxious, whereas feeling slowed down, fatigue/low energy, “pressure in head” (males only), and headache (females only) were most frequently reported during postexertion testing. Conclusion: An understanding of the common exertion-related symptoms at baseline in a laboratory or field-based setting in adolescents may be advantageous for clinicians as they manage individual recovery postconcussion. This is particularly important during an adolescent’s recovery and return to play when exertional testing may be implemented, especially since symptoms were reported pre and post exertional testing in both males and females regardless of concussion history.

Cerebral autoregulation (CA) refers to the control of cerebral tissue blood flow (CBF) in response to changes in perfusion pressure. Due to the challenges of measuring intracranial pressure, CA is often described as the relationship between mean arterial pressure (MAP) and CBF. Dynamic CA (dCA) can be assessed using multiple techniques, with transfer function analysis (TFA) being the most common. A 2016 white paper by members of an international Cerebrovascular Research Network (CARNet) that is focused on CA strove to improve TFA standardization by way of introducing data acquisition, analysis, and reporting guidelines. Since then, additional evidence has allowed for the improvement and refinement of the original recommendations, as well as for the inclusion of new guidelines to reflect recent advances in the field. This second edition of the white paper contains more robust, evidence-based recommendations, which have been expanded to address current streams of inquiry, including optimizing MAP variability, acquiring CBF estimates from alternative methods, estimating alternative dCA metrics, and incorporating dCA quantification into clinical trials. Implementation of these new and revised recommendations is important to improve the reliability and reproducibility of dCA studies, and to facilitate inter-institutional collaboration and the comparison of results between studies.

Currently, the standard approach for restricting exercise prior to cerebrovascular data collection varies widely between 6 and 24 h. This universally employed practice is a conservative approach to safeguard physiological alterations that could potentially confound one’s study design. Therefore, the purpose of this systematic review was to amalgamate the existing literature examining the extent and duration of postexercise alterations in cerebrovascular function, measured via transcranial Doppler ultrasound. Furthermore, an exploratory aim was to scrutinize and discuss common biases/limitations in the previous studies to help guide future investigations. Search strategies were developed and imported into PubMed, SPORTDiscus, and Medline databases. A total of 595 records were screened and 35 articles met the inclusion criteria in this review, which included assessments of basic cerebrovascular metrics ( n = 35), dynamic cerebral autoregulation (dCA; n = 9), neurovascular coupling (NVC; n = 2); and/or cerebrovascular reactivity (CVR-CO2; n = 1) following acute bouts of aerobic exercise. Across all studies, it was found that NVC was impacted for 1 h, basic cerebrovascular parameters and CVR-CO2 parameters for 2 h, and dCA metrics for 6 h postexercise. Therefore, future studies can provide participants with these evidence-based time restrictions, regarding the minimum time to abstain from exercise prior to data collection. However, it should be noted that other physiological mechanisms could still be altered (e.g., metabolic, hormonal, and/or autonomic influences), despite cerebrovascular function returning to baseline levels. Thus, future investigations should seek to control as many physiological influences when using cerebrovascular assessments, immediately following these time restraints. The main limitations/biases were lack of female participants, cardiorespiratory fitness, and consideration for vessel diameter.

The systematic review evaluated the evidence related to how physical activity affects recovery following a sport-related concussion (SRC) in adolescents. Databases indexed were PUBMED, MEDLINE, and SPORTDiscus. Inclusion criteria included 1) original research article, 2) ≥66% have an SRC diagnosed by a clinician, 3) human research, and 4) evaluated the effect of an SRC on physical activity in adolescents only (

Standard practices for quantifying neurovascular coupling (NVC) with transcranial Doppler ultrasound (TCD) require participants to complete one-to-ten repetitive trials. However, limited empirical evidence exists regarding how the number of trials completed influences the validity and reliability of temporally derived NVC metrics. Secondary analyses was performed on 60 young healthy participants (30 females/30 males) who completed eight cyclical eyes-closed (20-seconds), eyes-open (40-seconds) NVC trials, using the “Where’s Waldo?” visual paradigm. TCD data was obtained in posterior and middle cerebral arteries (PCA and MCA, respectively). The within-day (n = 11) and between-day ( n = 17) reliability were assessed at seven- and three-time points, respectively. Repeat testing from the reliability aims were also used for the concurrent validity analysis ( n = 160). PCA metrics (i.e., baseline, peak, percent increase, and area-under-the-curve) demonstrated five trials produced excellent intraclass correlation coefficient (ICC) 95% confidence intervals for validity and within-day reliability (>0.900), whereas between-day reliability was good-to-excellent (>0.750). Likewise, 95% confidence intervals for coefficient of variation (CoV) measures ranged from acceptable (

Cerebral hemodynamics, e.g., cerebral blood flow, can be measured and quantified using many different methods, with transcranial Doppler ultrasound (TCD) being one of the most commonly used approaches. In human physiology, the terminology used to describe metrics of cerebral hemodynamics are inconsistent and in some instances technically inaccurate; this is especially true when evaluating, reporting, and interpreting measures from TCD. Therefore, this perspective article presents recommended terminology when reporting cerebral hemodynamic data. We discuss the current use and misuse of the terminology in the context of using TCD to measure and quantify cerebral hemodynamics and present our rationale and consensus on the terminology that we recommend moving forward. For example, one recommendation is to discontinue the use of the term “cerebral blood flow velocity” in favor of “cerebral blood velocity” with precise indication of the vessel of interest. We also recommend clarity when differentiating between discrete cerebrovascular regulatory mechanisms, namely, cerebral autoregulation, neurovascular coupling, and cerebrovascular reactivity. This will be a useful guide for investigators in the field of cerebral hemodynamics research.

We previously reported subtle dynamic cerebral autoregulation (dCA) alterations following 6 weeks of high-intensity interval training (HIIT) to exhaustion using transfer function analysis (TFA) on forced mean arterial pressure (MAP) oscillations in young endurance-trained men. However, accumulating evidence suggests the cerebrovasculature better buffers cerebral blood flow changes when MAP acutely increases compared to when MAP acutely decreases. Whether HIIT affects the directional sensitivity of the cerebral pressure-flow relationship in these athletes is unknown. In 18 endurance-trained men (age: 27 ± 6 years, VO

Accumulating evidence suggests asymmetrical responses of cerebral blood flow during large transient changes in mean arterial pressure. Specifically, the augmentation in cerebral blood flow is attenuated when mean arterial pressure acutely increases, compared with declines in cerebral blood flow when mean arterial pressure acutely decreases. However, common analytical tools to quantify dynamic cerebral autoregulation assume autoregulatory responses to be symmetric, which does not seem to be the case. Herein, we provide the rationale supporting the notion we need to consider the directional sensitivity of large and transient mean arterial pressure changes when characterizing dynamic cerebral autoregulation.

Sinusoidal squat-stand maneuvers (SSM) without resistance have been shown to produce ~30-50 mmHg swings in mean arterial pressure which are largely buffered in the brain via dynamic cerebral autoregulation (dCA). This study aimed to further elucidate how this regulatory mechanism is affected during SSM with added resistance (~20% bodyweight). Twenty-five participants (sex/gender: 13 females/12 males) completed two bouts of 5-min SSM for both bodyweight and resistance conditions (10% bodyweight in each arm) at frequencies of 0.05 Hz (20-s squat/stand cycles) and 0.10 Hz (10-s squat/stand cycles). Middle and posterior cerebral artery (MCA/PCA) cerebral blood velocities were indexed with transcranial Doppler ultrasound. Beat-to-beat blood pressure (BP) was quantified via finger photoplesmography. Transfer function analysis was employed to quantify dCA in both cerebral arteries across the cardiac cycle (diastole, mean, and systole). Two-by-two Analysis of Variance with generalized eta squared effect sizes were utilized to determine differences between resistance vs. bodyweight squats and between sexes/genders. Absolute mean and diastolic BP were elevated during the resistance squats (p 0.001); however, only the BP point-estimate power spectrum densities were augmented at 0.10 Hz (p 0.048). No differences were noted for phase and gain metrics between bodyweight and resistance SSM (p 0.067); however, females displayed attenuated systolic regulation (p 0.003). Despite augmented systemic BP during resistance SSM, the brain was effective at buffering the additional stress to mitigate overperfusion/pressure. Females displayed less dCA regulation within the systolic aspect of the cardiac cycle, which may be associated with physiological underpinnings related to various clinical conditions/presentations.

Background: Near point of convergence (NPC) assesses the vergence ability of the visuo-oculomotor system; however, little is known regarding: the extent and duration exercise impacts NPC and the be...

A simple bodyweight squat is sufficient to cause substantial stress on the autonomic nervous system (ANS) via ~30-50 mmHg blood pressure (BP) oscillations. However, it is unknown to the extent of the ANS is impacted during and immediately following bodyweight and resistance squat-stand maneuvers (SSM) while considering chromosomal sex. Thirteen females and twelve males performed four, 5-minute bouts of squat-stand maneuvers (SSM); two at 0.05 Hz (10-second squat/10-second stand) and two at 0.10 Hz (5-s squat/5-s stand). The SSM were performed using bodyweight resistance and additional external resistance (~20% of bodyweight). Five-minutes of quiet-sitting and quiet-standing were completed immediately following both bodyweight and resistance squats. Heart rate variability (HRV) and baroreceptor sensitivity metrics were extracted from beat-to-beat electrocardiography and systemic BP recordings. Repeated measure Analysis of Variance with generalized eta-squared effect sizes assessed differences between SSM task type and chromosomal sex on ANS metrics. Despite added resistance eliciting greater elevations in blood pressure, no differences in ANS function were noted during competition and recovery between SSM tasks (all p 0.050; negligible/small effect sizes). During recovery, females had an elevated heart rate (p = 0.017; small effect size), greater time-domain HRV measures (p 0.047; small effect size), greater high-frequency domain HRV measures (p = 0.002; moderate effect size), and reduced low-frequency domain HRV measures (p = 0.002; moderate effect size). A healthy ANS can modulate repetitive cardiovascular stressors via squat-stand maneuvers in a harmonious manner irrespective of added low-level resistance. Females were more parasympathetically driven following low-level resistance exercise/stress, which may be a cardioprotective trait.

What is the central question of this study? Does habitual exercise modality affect the directionality of the cerebral pressure-flow relationship? What is the main finding and its importance? These data suggest the hysteresis-like pattern of dynamic cerebral autoregulation appears present in long-term sedentary and endurance-trained individuals, but absent in resistance-trained individuals. This is the first study to expand knowledge on the directional sensitivity of the cerebral pressure-flow relationship to trained populations.Evidence suggests the cerebrovasculature may be more efficient at dampening cerebral blood flow (CBF) variations when mean arterial pressure (MAP) transiently increases, compared to when it decreases. Despite divergent MAP and CBF responses to acute endurance and resistance training, the long-term impact of habitual exercise modality on the directionality of dynamic cerebral autoregulation (dCA) is currently unknown. Thirty-six young healthy participants (sedentary (n = 12), endurance-trained (n = 12), and resistance-trained (n = 12)) undertook a 5-min repeated squat-stand protocol at two forced MAP oscillation frequencies (0.05 and 0.10 Hz). Middle cerebral artery mean blood velocity (MCAv) and MAP were continuously monitored. We calculated absolute (ΔMCAv

We recently employed repeated squat-stands (RSS) to quantify directional sensitivity of the cerebral-pressure flow relationship (i.e. hysteresis) using a novel metric. Within-day reproducibility and diurnal variation impacts of this metric are unknown. We evaluated this metric for: 1) within-day reproducibility and the extent diurnal variation has in middle (MCA; ΔMCAvT/ΔMAPT) and posterior cerebral arteries (PCA; ΔPCAvT/ΔMAPT); 2) sex differences. Absolute (ΔMCAvT/ΔMAPT ; ΔPCAvT/ΔMAPT) and relative (%MCAvT/%MAPT, %PCAvT/%MAPT) metrics were calculated at seven time-points (08:00-17:00) in 18 participants (8 women; 24 ± 3 yrs) using the minimum-to-maximum MCAv/PCAv and MAP for each RSS at 0.05 Hz and 0.10 Hz. Reproducibility was evaluated with intraclass correlation coefficient (ICC). For all metrics, reproducibility was good (0.75-0.90) to excellent (>0.90). The metric in both arteries was impacted by MAP direction at 0.10 Hz (all p < 0.024). Time-of-day influenced ΔMCAvT/ΔMAPT (0.05 Hz: p = 0.0028; 0.10 Hz: p = 0.0009), %MCAvT/%MAPT (0.05 Hz: p = 0.035; 0.10 Hz: p = 0.0087), and ΔPCAvT/ΔMAPT (0.05 Hz: p = 0.0236). Sex differences in the MCA (p = 0.0028) vanished in relative terms and was absent in the PCA. These findings demonstrate within-day reproducibility of this metric in both arteries. Moreover, hysteresis is not impacted by sex.

Objective: This study examined the extent symptoms associated with potential traumatic brain injury (TBI) in intimate partner violence (IPV) survivors overlap with sport-related concussions...

This study examined cerebral blood flow (CBF) and its regulation before and after a short-term periodized aerobic exercise training intervention in patients with chronic obstructive pulmonary disease (COPD). Twenty-eight patients with COPD (forced expiratory volume in 1 s/forced vital capacity < 0.7 and −1·mmHg−1, P = 0.02). After aerobic training, absolute peak O2 consumption increased in both groups, with a greater improvement in control subjects (1.7 ± 0.4 vs. 4.1 ± 0.2 ml·kg−1·min−1, respectively, P = 0.001). Despite these improvements in peak O2 consumption, there were no significant alterations in CBF or any measures of cerebrovascular function after exercise training in either group. In conclusion, patients with COPD have a blunted cerebrovascular response to hypocapnia, and 8 wk of aerobic exercise training did not alter cerebrovascular function despite significant improvements in cardiorespiratory fitness. NEW & NOTEWORTHY No study to date has investigated whether exercise training can alter resting cerebral blood flow (CBF) regulation in patients with chronic obstructive pulmonary disease (COPD). This study is the first to assess CBF regulation at rest, before, and after aerobic exercise training in patients with COPD and healthy control subjects. This study demonstrated that while exercise training improved aerobic fitness, it had little effect on CBF regulation in patients with COPD or control subjects.

In 1959, Niels Lassen illustrated the cerebral autoregulation curve in the classic review article entitled Cerebral Blood Flow and Oxygen Consumption in Man. This concept suggested a relatively broad mean arterial pressure range (~60–150 mmHg) wherein cerebral blood flow remains constant. However, the assumption that this wide cerebral autoregulation plateau could be applied on a within‐individual basis is incorrect and greatly variable between individuals. Indeed, each data point on the autoregulatory curve originated from independent samples of participants and patients and represented interindividual relationships between cerebral blood flow and mean arterial pressure. Nonetheless, this influential concept remains commonly cited and illustrated in various high‐impact publications and medical textbooks, and is frequently taught in medical and science education without appropriate nuances and caveats. Herein, we provide the rationale and additional experimental data supporting the notion we need to lose this dogmatic view of cerebral autoregulation., In 1959, Niels Lassen illustrated the cerebral autoregulation curve in the classic review article entitled Cerebral Blood Flow and Oxygen Consumption in Man. This concept suggested a relatively broad mean arterial pressure range wherein cerebral blood flow remains constant. Herein, we provide the rationale and additional experimental data supporting the notion we need to lose this dogmatic view of cerebral autoregulation.

Hysteresis in the cerebral pressure-flow relationship describes the superior ability of the cerebrovasculature to buffer cerebral blood flow changes when mean arterial pressure (MAP) acutely increases compared to when MAP acutely decreases. This phenomenon can be evaluated by comparing the change in middle cerebral artery mean blood velocity (MCAv) per change in MAP during either acute increases or decreases in MAP induced by repeated squat-stands (RSS). However, no real baseline can be employed for this particular protocol as there is no true stable reference point. Herein, we characterized a novel metric using the greatest MAP oscillations induced by RSS without using an independent baseline value and adjusted for time intervals (ΔMCAvT/ΔMAPT). We also examined whether this metric during each RSS transition were comparable between each other over a 5-min period. ΔMCAvT/ΔMAPTwas calculated using the minimum to maximum MCAv and MAP for each RSS performed at 0.05 Hz and 0.10 Hz. We compared averaged ΔMCAvT/ΔMAPTduring MAP increases and decreases in 74 healthy subjects [9 women; 32 ± 13 years]. ΔMCAvT/ΔMAPTwas lower for MAP increases than MAP decreases at 0.10 Hz RSS only (0.91 ± 0.34 vs. 1.01 ± 0.44 cm·s-1/mmHg; p = 0.0013). For both frequency and MAP direction, time during RSS had no effect on ΔMCAvT/ΔMAPT. This novel analytical method supports the use of the RSS model to evaluate the directional sensitivity of the pressure-flow relationship. These results contribute to the importance of considering the direction of MAP changes when evaluating dynamic cerebral autoregulation.News & NoteworthyRepeated squat-stand maneuvers are able to examine the directional sensitivity of the cerebral pressure-flow relationship. These maneuvers induce stable physiological cyclic changes where brain blood flow changes with blood pressure increases are buffered more than decreases. These results highlight the importance of considering directional blood pressure changes within cerebral autoregulation.

While cardiac pulsations are widely present within physiological and neuroimaging data, it is unknown the extent this information can provide valid and reliable heart rate and heart rate variability (HRV) estimates. The objective of this study was to demonstrate how a slight temporal shift due to an insufficient sampling frequency can impact the validity/accuracy of deriving cardiac metrics.Twenty-two participants were instrumented with valid/reliable industry-standard or open-source electrocardiograms. Five-minute lead II recordings were collected at 1000 Hz in an upright orthostatic position. Following artifact removal, the 1000 Hz recording for each participant was downsampled to frequencies ranging 2-500 Hz. The validity of each participant's downsampled recording was compared against their 1000 Hz recording ("reference-standard") using Bland-Altman plots with 95 % limits of agreement (LOA), coefficient of variation (CoV), intraclass correlation coefficients, and adjusted r-squared values.Downsampled frequencies of ≥ 50 and ≥ 90 Hz produced highly robust measures with narrow log-transformed 95 % LOA (±0.01) and low CoV values (≤3.5 %) for heart rate and HRV metrics, respectively. Below these thresholds, the log-transformed 95 % LOA became wider (LOA range: ±0.1-1.9) and more variable (CoV range: 1.5-111.6 %).These results provide an important consideration for obtaining cardiac information from physiological data. Compared to the "reference-standard" ECG, a seemingly negligible temporal shift of the systolic contraction (R wave) greater than 11-milliseconds (90 Hz) away from its true value, lessened the validity of the HRV. Further research is warranted to determine the minimum sampling frequency required to obtain valid heart rate/HRV metrics from pulsatile waveforms.

A one size fits all methodological approach to quantify HRV metrics appears to be inappropriate, where study design considerations need to be conducted upon a variable-by-variable basis. The present results found 60 s (heart rate), 240 s (time-domain parameters), and 300 s (relative frequency-domain parameters) were required to obtain accurate and reproducible metrics. The lower validity/reliability of the ultra-short-term metrics was attributable to measurement error and/or confounding from extraneous physiological influences (i.e., respiratory and hemodynamic variables).

There is growing concern repetitive head contacts sustained by soccer players may lead to long-term health ramifications. Therefore, this preliminary investigation examined the impact an acute soccer heading bout has on dynamic cerebral autoregulation (dCA) metrics.In this preliminary investigation, 40 successful soccer headers were performed in 20 min by 7 male elite soccer players (24.1 ± 1.5 years). Soccer balls were launched at 77.5 ± 3.7 km/h from JUGS soccer machine, located 35 m away from participants. Linear and rotational head accelerations impacts were measured using an accelerometer (xPatch). The SCAT3 indexed concussion symptom score and severity before and after: soccer headers, sham (body contact only), and control conditions. Squat-stand maneuvers were performed at 0.05 Hz and 0.10 Hz to quantity dCA through measures of coherence, phase, and gain.Cumulative linear and rotational accelerations during soccer headers were 1574 ± 97.9 g and 313,761 ± 23,966 rads/sThese preliminary results indicate an acute bout of soccer heading resulted in alterations to dCA metrics. Therefore, future research with larger sample sizes is warranted to fully comprehend short- and long-term physiological changes related to soccer heading.

Objective: The current investigation examined how a bout of soccer heading may impact brain function. Design: Semi-randomized crossover cohort. Setting: Controlled soccer heading. Participants: Seven male soccer players (24.1 ± 1.5 years). Intervention: 40 successful soccer headers were performed in 20 min (25 m, launch velocity ~80 km/h). X2 xPatch recorded linear and rotational head accelerations during each impact. A contact control “sham” condition – ball made body contact, but not by the head; and a no activity time “control” condition were also completed. Main Outcome Measures: Posterior and middle cerebral artery (PCA and MCA, respectively), cerebral blood velocity (CBV) was recorded during a visual task (neurovascular coupling: NVC) alongside SCAT3 symptoms scores pre/post a controlled bout of soccer heading. Results: Cumulative linear and rotational accelerations were 1,574 ± 97.9 g and 313,761 ± 23,966 rads/s2, respectively, during heading and changes in SCAT3 symptom number (pre: 2.6 ± 3.0; post: 6.7 ± 6.2, p = 0.13) and severity (pre: 3.7 ± 3.6, post: 9.4 ± 7.6, p = 0.11) were unchanged. In the PCA, no NVC differences were observed, including: relative CBV increase (28.0 ± 7.6%, p = 0.71) and total activation (188.7 ± 68.1 cm, p = 0.93). However, MCA-derived NVC metrics were blunted following heading, demonstrating decreased relative CBV increase (7.8 ± 3.1%, p = 0.03) and decreased total activation (26.7 ± 45.3 cm, p = 0.04). Conclusion: Although an acute bout of soccer heading did not result in an increase of concussion-like symptoms, there were alterations in NVC responses within the MCA during a visual task. This suggests an acute bout of repetitive soccer heading can alter CBV regulation within the region of the brain associated with the header impacts.

A common inclusion criterion when assessing cerebrovascular (CVR) metrics is for individuals to abstain from exercise for 12–24 hr prior to data collections. While several studies have examined CVR during exercise, the literature describing CVR throughout post‐exercise recovery is sparse. The current investigation examined CVR measurements in nine participants (seven male) before and for 8 hr following three conditions: 45‐min moderate‐continuous exercise (at ~50% heart‐rate reserve), 25‐min high‐intensity intervals (ten, one‐minute intervals at ~85% heart‐rate reserve), and a control day (30‐min quiet rest). The hypercapnic (40–60 mmHg) and hypocapnic (25–40 mmHg) slopes were assessed via a modified rebreathing technique and controlled stepwise hyperventilation, respectively. All testing was initiated at 8:00a.m. with transcranial Doppler ultrasound measurements to index cerebral blood velocity performed prior to the condition (pre) with serial follow‐ups at zero, one, two, four, six, and eight hours within the middle and posterior cerebral artery (MCA, PCA). Absolute and relative MCA and PCA hypercapnic slopes were attenuated following high‐intensity intervals at hours zero and one (all p .13), aside from a reduced relative hypercapnic MCA slope at hours zero and one following moderate‐continuous exercise (all p, Absolute and relative MCA and PCA cerebrovascular reactivity hypercapnic slopes were attenuated following high‐intensity intervals at hours zero and one (all p .13), aside from a reduced relative hypercapnic MCA slope at hours zero and one following moderate‐continuous exercise (all p

Numerous studies have examined heart rate variability (HRV) and cardiac baroreceptor sensitivity (BRS) variables during recovery both acutely (under 3 h) and long-term (24, 48, and 72 h) postexercise. However, there is little literature examining HRV and BRS measures between these timepoints. Spontaneous short-term HRV and cardiac BRS measures were collected in 9 participants before and at zero, 1, 2, 4, 6, and 8 h after 3 separate conditions: moderate-intensity continuous exercise (MICE; 45 min at 50% heart rate reserve), high-intensity interval exercise (HIIE; 25 min including ten 1-min intervals at 85% heart rate reserve), and control (30 min quiet rest). HRV measures in the time domain were only affected immediately following HIIE and MICE at hour zero (all p < 0.043), whereas frequency-domain metrics were unaltered (all p > 0.102). These measures were highly consistent across the control day (all p > 0.420). Cardiac BRS was assessed via low-frequency (LF) gain, and revealed reductions following HIIE at hour zero (p < 0.012). Cardiac BRS LF gain remained consistent following MICE and control interventions (all p > 0.280). The common practice of waiting 12 to 24 h is overly conservative as the current findings demonstrate measures return to baseline at ∼60 min after exercise. Moreover, these metrics demonstrated high levels of within- and between-day reliability. Novelty Previously a 12-h minimum restriction from exercise was required before participation in HRV/BRS studies. Recovery from moderate-intensity exercise for HRV and BRS metrics was

Objective To determine the effects of repetitive subconcussive head trauma on neurovascular coupling (NVC) responses. Design Prospective cohort study collected between September 2013 and December 2016. Setting University laboratory. Participants One hundred seventy-nine elite, junior-level (age, 19.6 ± 1.5 years) contact sport (ice hockey, American football) athletes recruited for preseason testing. Fifty-two nonconcussed athletes returned for postseason testing. Fifteen noncontact sport athletes (age, 20.4 ± 2.2 years) also completed preseason and postseason testing. Exposure(s) Subconcussive sport-related head trauma. Main outcome measures Dynamics of NVC were estimated during cycles of 20 seconds eyes closed and 40 seconds eyes open to a visual stimulus (reading) by measuring cerebral blood flow (CBF) velocity in the posterior (PCA) and middle (MCA) cerebral arteries via transcranial Doppler ultrasound. Results Both athlete groups demonstrated no significant differences in PCA or MCA NVC dynamics between preseason and postseason, despite exposure to a median of 353.5 (range, 295.0-587.3) head impacts (>2g) over the course of the season for contact sport athletes. Conclusions Within the context of growing concern over detrimental effects of repetitive subconcussive trauma, the current results encouragingly suggest that the dynamics of NVC responses are not affected by 1 season of participation in junior-level ice hockey or American football. This is an important finding because it indicates an appropriate postseason CBF response to elevated metabolic demand with increases in neural activity.

KEY POINTS: Chronic mountain sickness (CMS) is a maladaptation syndrome encountered at high altitude (HA) characterised by severe hypoxaemia that carries a higher risk of stroke and migraine and is associated with increased morbidity and mortality. We examined if exaggerated oxidative‐inflammatory‐nitrosative stress (OXINOS) and corresponding decrease in vascular nitric oxide bioavailability in patients with CMS (CMS+) is associated with impaired cerebrovascular function and adverse neurological outcome. Systemic OXINOS was markedly elevated in CMS+ compared to healthy HA (CMS−) and low‐altitude controls. OXINOS was associated with blunted cerebral perfusion and vasoreactivity to hypercapnia, impaired cognition and, in CMS+, symptoms of depression. These findings are the first to suggest that a physiological continuum exists for hypoxaemia‐induced systemic OXINOS in HA dwellers that when excessive is associated with accelerated cognitive decline and depression, helping identify those in need of more specialist neurological assessment and targeted support. ABSTRACT: Chronic mountain sickness (CMS) is a maladaptation syndrome encountered at high altitude (HA) characterised by severe hypoxaemia that carries a higher risk of stroke and migraine and is associated with increased morbidity and mortality. The present cross‐sectional study examined to what extent exaggerated systemic oxidative‐inflammatory‐nitrosative stress (OXINOS), defined by an increase in free radical formation and corresponding decrease in vascular nitric oxide (NO) bioavailability, is associated with impaired cerebrovascular function, accelerated cognitive decline and depression in CMS. Venous blood was obtained from healthy male lowlanders (80 m, n = 17), and age‐ and gender‐matched HA dwellers born and bred in La Paz, Bolivia (3600 m) with (CMS+, n = 23) and without (CMS−, n = 14) CMS. We sampled blood for oxidative (electron paramagnetic resonance spectroscopy, HPLC), nitrosative (ozone‐based chemiluminescence) and inflammatory (fluorescence) biomarkers. We employed transcranial Doppler ultrasound to measure cerebral blood flow (CBF) and reactivity. We utilised psychometric tests and validated questionnaires to assess cognition and depression. Highlanders exhibited elevated systemic OXINOS (P < 0.05 vs. lowlanders) that was especially exaggerated in the more hypoxaemic CMS+ patients (P < 0.05 vs. CMS−). OXINOS was associated with blunted cerebral perfusion and vasoreactivity to hypercapnia, impaired cognition and, in CMS+, symptoms of depression. Collectively, these findings are the first to suggest that a physiological continuum exists for hypoxaemia‐induced OXINOS in HA dwellers that when excessive is associated with accelerated cognitive decline and depression, helping identify those in need of specialist neurological assessment and support.

The central nervous system preplans postural responses to successfully perform complex multi-joint movements. These responses have been termed anticipatory postural adjustments (APAs), and they constitute a general type of response to stabilize posture prior to movement initiation. APA sequences are elicited with shorter latency when a startling acoustic stimulus is applied, demonstrating their preplanned nature. Increasing task complexity using a simple reaction time (RT) paradigm has been shown to delay limb movement RT as a result of additional planning or sequencing requirements; however, the effect of task complexity on APA dynamics is unclear. The purpose of the present study was to investigate if task complexity modulates APA onset in a manner analogous to that observed in the primary effector. 13 participants completed 150 trials of simple (1-target) and complex (2- or 3-target) arm movements while standing on a force plate. Results indicated participants had significantly faster arm movement RTs in the simple versus the most complex condition. Similar to the primary effector, APA RTs were longer in the most complex (3-target) movement compared to both the 1-target and 2-target movements. Furthermore, APA excursion velocities were scaled to the complexity of the upcoming movement: the rate of APAs increased from simplest to most complex movements. These findings clearly demonstrate APAs are sensitive to task complexity, further elucidating their preplanned role in stabilizing posture which enables the successful completion of intended movements.

Ocular near point of convergence (NPC) has been shown to be sensitive to the effects of concussion and subconcussive impacts. To determine if NPC is also sensitive to a previous history of concussion, male contact-sport athletes either with (n=26) or without (n=16) a history of at least one previous concussion had their NPC assessed. The results showed that participants with a history of concussion displayed NPC values (9.4±1.6 cm) indistinguishable from those with no history of concussion (8.4±2.1 cm, t-test, p=0.09). This was the case regardless of whether 1, 2, or 3 or more concussions had occurred and despite the fact participants with concussion (mean time since last concussion: 1136 days) suffered from an increased number and severity of symptoms as assessed with the SCAT 3 (3.6±2.2 vs. 2.13±1.89 symptoms, 6.1±4.1 vs. 3.19±2.99 severity, t-test, p

In the present study we investigated how attention contributes to the interaction between reach planning and execution, and postural control. Reaching movements were generated while standing and were performed either in isolation or in conjunction with a secondary reaction time (RT) task. In addition, to better understand how online movement control is affected by this interaction, the reaching movements could be unexpectedly perturbed medial-laterally. Postural kinetic, arm kinematic and RT, and secondary RT measures were used to characterize the responses. Results indicate task performance worsened when both the reaching and secondary tasks were completed simultaneously. Our results imply the generation of reaching movements while standing requires attentional resources to properly coordinate the interaction between the reaching task and postural control.

Background Heart rate variability (HRV) is a popular tool to quantify autonomic function. However, this typically requires an expensive 3–12 lead electrocardiogram (ECG) and BioAmp system. This investigation sought to determine the validity and reliability of an OpenBCI cyton biosensing board (open source) for accurately quantifying HRV. New method A cyton board with a 3-lead ECG was employed to acquire heart rate waveform data, which was processed to obtain HRV within both time- and frequency-domains. The concurrent validity was compared to a simultaneous recording from an industry-standard 3-lead ECG (ADInstruments) (n = 15). The reliability of the cyton board was compared between three days within a 7-day timespan (n = 10). Upright quiet-stance short-term HRV metrics were quantified in time- and frequency-domains. Results The two devices displayed excellent limits of agreements (all log mean differences ±0.4) and very high between-device variable associations (all r2 > 0.98). Between the three time points in the same subjects, no differences were noted within time- (all p > 0.71) or frequency-domains (all p > 0.88) across testing points. Finally, all HRV metrics exhibited excellent levels of reliability through high Cronbach's Alpha (all ≥0.916) and intraclass correlation coefficients (all ≥0.930); and small standard error of the measurement (all ≤0.7) and typical error of the measurement (all ≤0.1) metrics. Comparison with existing methods The cyton board with 3-lead ECG was compared with an industry-standard ADInstruments ECG during HRV assessments. There were no significant differences between devices with respect to time- and frequency-domains. The cyton board displayed high-levels of between-day reliability and provided values harmonious to previous ECG literature highlighting the applicability for longitudinal studies. Conclusion With proper background knowledge regarding ECG principles and a small degree of set-up complexity, an open source cyton board can be created and employed to perform multimodal HRV assessments at a fraction of the cost (~4%) of an industry-standard ECG setup., Heart rate variability, Electrocardiography, Cyton board, Open source, Validity, Reliability.

Women exhibit higher prevalence of orthostatic hypotension with presyncopal symptoms compared to men. These symptoms could be influenced by an attenuated ability of the cerebrovasculature to respond to rapid changes in blood pressure (BP) [dynamic cerebral autoregulation (dCA)]. However, the influence of sex on dCA remains equivocal. We compared dCA in 11 women (25 ± 2 y) and 11 age-matched men (24 ± 1 y) using a multimodal approach including a sit-to-stand maneuver and forced oscillations (5 min of squat-stand performed at 0.05 and 0.10 Hz). The prevalence of initial orthostatic hypotension (IOH; decrease in systolic ≥ 40 mmHg and/or diastolic BP ≥ 20 mmHg) during the first 15 sec of sit-to-stand was determined as a functional outcome. In women, the decrease in mean middle cerebral artery blood velocity (MCAvmean) following the sit-to-stand was greater (−20 ± 8 vs. -11 ± 7 cm sec-1; p=0.018) and the onset of the regulatory change (time lapse between the beginning of the sit-to-stand and the increase in the conductance index (MCAvmean/mean arterial pressure(MAP)) was delayed (p=0.007). Transfer function analysis gain during 0.05 Hz squat-stand was ∼48% higher in women (6.4 ± 1.3 vs. 3.8 ± 2.3 sec; p=0.017). The prevalence of IOH was comparable between groups (4/9 vs. 5/9, p=0.637). These results indicate the cerebrovasculature of healthy women has an attenuated ability to react to large and rapid changes in BP in the face of preserved orthostasis, which could be related to a higher cerebrovascular reserve to face a rapid transient hypotension.NEWS & NOTEWORTHYThe novel findings of this study are that healthy women have impaired dynamic cerebral autoregulation, although the prevalence of orthostatic intolerance was similar in women and men. These results indicate the cerebrovasculature of healthy women has an attenuated ability to react to large and rapid changes in blood pressure in the face of preserved orthostasis, which could be related to a higher cerebrovascular reserve to face a rapid transient hypotension.

ObjectivesTo determine the effect of heading a soccer ball on serum neurofilament light (NF-L) protein, plasma tau protein and symptom metrics including total number of symptoms reported and symptom severity scores on the Standardized Concussion Assessment Tool— 3rd edition (SCAT3).MethodsEleven male collegiate soccer players were recruited to take part in three experimental conditions including heading, sham and control conditions. Participants were required to perform 40 headers in 20 min in the heading condition, and control 40 soccer balls directed at them with their hands, chest or thigh in the sham condition. No ball contact was made during the control condition. Blood sampling and SCAT3 symptom assessments were completed prior to and 1 hour following conditions. A subset of participants returned 3 weeks following the heading condition for blood sampling.ResultsNF-L was elevated at 1 hour (p=0.004) and 1 month (p=0.04) following the heading condition, and at 1 hour (p=0.02) following the control condition. Tau levels remained unchanged following all conditions. The total number of symptoms (TS) and symptom severity (SS) scores from the SCAT3 were both elevated following the heading condition (p=0.01 and p=0.03, respectively). Both TS and SS decreased following sham (p=0.04 and p=0.04) and control conditions (p=0.04 and p=0.04).ConclusionAn acute bout of soccer heading is associated with increased NF-L concentrations at 1 hour and 1 month following the session and can lead to symptoms commonly reported following sport-related concussion.

Cerebral pressure-flow dynamics are typically reported between mean arterial pressure and mean cerebral blood velocity. However, by reporting only mean responses, potential differential regulatory properties associated with systole and diastole may have been overlooked.Twenty young adults (16 male, age: 26.7 ± 6.6 years, BMI: 24.9 ± 3.0 kg/mThere were main effects for both cardiac cycle and frequency for phase and gain metrics (p0.001). The systolic phase (mean ± SD) was elevated at 0.05 (1.07 ± 0.51 radians) and 0.10 Hz (0.70 ± 0.46 radians) compared to the diastolic phase (0.05 Hz: 0.59 ± 0.14 radians; 0.10 Hz: 0.33 ± 0.11 radians). Conversely, the systolic normalized gain was reduced (0.05 Hz: 0.49 ± 0.12%/%; 0.10 Hz: 0.66 ± 0.20%/%) compared to the diastolic normalized gain (0.05 Hz: 1.46 ± 0.43%/%; 0.10 Hz: 1.97 ± 0.48%/%).These findings indicate there are differential systolic and diastolic aspects of the cerebral pressure-flow relationship. The oscillations associated with systole are extensively buffered within the cerebrovasculature, whereas diastolic oscillations are relatively unaltered. This indicates that the brain is adapted to protect itself against large increases in systolic blood pressure, likely as a mechanism to prevent cerebral haemorrhages.

To determine whether acute sports-related concussion (SRC) exerts differential effects on cerebral autoregulatory properties during systole versus diastole.One hundred and thirty-six contact-sport athletes tested preseason; 14 sustained a concussion and completed follow-up testing at 72 hours, 2 weeks, and 1 month post-injury. Five minutes of repetitive squat-stand maneuvers induced blood pressure (BP) oscillations at both 0.05 and 0.10 Hz. Beat-by-beat peak-systolic and end-diastolic BP (sysBP/ diasBP) and middle cerebral artery blood velocity (sysMCAv/diasMCAv) were recorded using finger photoplethysmography and transcranial Doppler ultrasound, respectively. Relationships between sysBP-sysMCAv and diasBP-diasMCAv were quantified using transfer function analysis to estimate coherence (correlation), gain (response magnitude), and phase (response latency).Significant main effects of the cardiac cycle were observed across all outcome metrics. A significant main effect of SRC was observed for 0.10 Hz phase: systolic and diastolic phases were reduced at 72 h (21.8 ± 5.2%) and 2 weeks (22.7 ± 7.1%) compared to preseason but recovered by 1 month. Concussion significantly impaired diastolic, but not systolic, gain: 0.10 Hz diastolic gain was increased (27.2 ± 7.7%) at 2 weeks, recovering by 1 month.Impairments in autoregulatory capacity, observed for a transient period following SRC that persist beyond symptom resolution and clinical recovery, appear to be differentially affected across the cardiac cycle. Similar patterns of impairment were observed for systolic and diastolic phases (response latency); however, normalized gain (response magnitude) impairments were identified only in diastole. These findings may explain the increased cerebral vulnerability as well as exercise-induced symptom exacerbation observed post-SRC.

We examined the between-day reproducibility of active (squat-stand maneuvers)- and passive [oscillatory lower-body negative pressure (OLBNP) maneuvers]-driven oscillations in blood pressure. These relationships were examined in both younger ( n = 10; 25 ± 3 yr) and older ( n = 9; 66 ± 4 yr) adults. Each testing protocol incorporated rest (5 min), followed by driven maneuvers at 0.05 (5 min) and 0.10 (5 min) Hz to increase blood-pressure variability and improve assessment of the pressure-flow dynamics using linear transfer function analysis. Beat-to-beat blood pressure, middle cerebral artery velocity, and end-tidal partial pressure of CO2 were monitored. The pressure-flow relationship was quantified in the very low (0.02-0.07 Hz) and low (0.07–0.20 Hz) frequencies (LF; spontaneous data) and at 0.05 and 0.10 Hz (driven maneuvers point estimates). Although there were no between-age differences, very few spontaneous and OLBNP transfer function metrics met the criteria for acceptable reproducibility, as reflected in a between-day, within-subject coefficient of variation (CoV) of

Objective: To determine whether acute sports-related concussion (SRC) exerts differential effects on cerebral autoregulatory properties during systole versus diastole.

Objective: Cerebral pressure-flow dynamics are typically reported between mean arterial pressure and mean cerebral blood velocity. However, by reporting only mean responses, potential differential regulatory properties associated with systole and diastole may have been overlooked.

Although balance control has been studied extensively following acute concussion, little is known regarding repetitive sub-concussive head impacts or chronic exposure to multiple concussive events. Quiet stance postural control was characterized in contact sport athletes at pre-season (n = 135) and post-season (n = 48) to evaluate the effects of subconcussive trauma to the head. To determine the impact of acute concussion on postural control, athletes diagnosed with a concussion during the season (n = 12) were tested at 72-h, 2-weeks, and 1-month post-injury. Because only 4 of the concussed athletes completed baseline testing, control athletes (n = 12) matched for sport, age, body mass index (BMI), and previous concussion history served as a comparison group. Finally, the effects of previous concussion history on quiet stance postural control were determined by comparing pre-season data in contact sport athletes with either zero (Hx0, n = 50) or three or more (Hx3+, n = 25) previous concussions. A force plate was used to compare changes in centre-of-pressure root-mean-square displacement (RMSdisp) and mean-velocity (COPvel) in the anterior/posterior (AP) and medial/lateral (ML) directions. One-minute trials were performed with feet hip-width apart, hands-on-hips, and A) eyes-open and B) eyes-closed. Biomechanical head-impact exposure (impacts over 10 g) was indexed over the season using mastoid-fixed impact sensors. In acutely injured athletes, repeated-measures ANOVA revealed a significant effect of time for RMSdisp AP with increased displacement at 2 weeks compared to 72 h (p = 0.008, 95% CI: −0.180, −0.310 cm). No other COP variables were affected by acute concussion. Moreover, there was no effect of concussion history or repeated sub-concussive impacts on any quiet stance metric. Additionally, head-impact exposure metrics were not correlated with COP metrics. Taken together, the data suggests alterations in COP sway during quiet stance persist in the acute 2-week period after injury. These findings were not present with either a history of multiple concussions or exposure to sub-concussive head impacts indicating acute concussion does not have appear to have long term effects for these measures.

The cerebrovasculature is more efficient at compensating for pharmacologically induced transient hypertension versus transient hypotension. Whether this phenomenon exists during nonpharmacologically induced hypertension and hypotension is currently unknown. We compared the percent change in mean velocity in the middle cerebral artery (MCAvmean) per percent change in mean arterial pressure (MAP) (%ΔMCAVmean/%ΔMAP) during transient hypertension and hypotension induced during squat-stand maneuvers performed at 0.05 Hz (20-s cycles) and 0.10 Hz (10-s cycles) in 58 male volunteers. %ΔMCAvmean/%ΔMAP was attenuated by 25% ( P = 0.03, 0.05 Hz) and 47% ( P < 0.0001, 0.10 Hz) during transient hypertension versus hypotension. Thus, these findings indicate that the brain in healthy men is better adapted to compensate for physiologically relevant transient hypertension than hypotension. NEW & NOTEWORTHY The novel finding of this study is that the change in middle cerebral artery mean flow velocity is attenuated during hypertension compared with hypotension physiologically induced by oscillations in blood pressure in men. These results support that the human brain is more effective at compensating for transient hypertension than hypotension.

Background The concept of neurovascular coupling has been postulated since the late 1800s and has been demonstrated most commonly in humans using visual stimuli (e.g. reading, checkerboards). These traditional paradigms evoke only a moderate cerebral blood flow response due to the relative simplicity of the visual stimuli. New method Forty subjects completed three visual paradigms each challenging the visual processing areas to a different extent: reading text, complicated visual searching (new method: Where ’ s Waldo ) and viewing coloured dots. Posterior and middle cerebral artery (PCA, MCA) velocities were recorded using transcranial Doppler ultrasound during each visual paradigm. Results Prior to the presentation of the visual stimuli there were no differences in mean arterial pressure, or PCA or MCA velocities for the three paradigms. All three paradigms led to an elevation in PCA and MCA velocities after a delay (∼1.1 s). Whereas velocity elevation was consistent across the three paradigms in the MCA, it was markedly larger during the Where ’ s Waldo task in the PCA. Thus, although the onset of the neurovascular coupling response was similar across the three visual paradigms, its overall magnitude was stimulus-dependent. Comparison with existing methods Given that PCA velocity can be affected by blood pressure or carbon dioxide alterations, traditional neurovascular coupling paradigms (e.g. reading, checkerboards) appear to have a lower signal-to-noise ratio than that observed in complicated visual search tasks such as Where ’ s Waldo. Conclusions We recommend complicated visual search paradigms such as Where ’ s Waldo be considered for future transcranial Doppler-based neurovascular coupling studies.

Objective Examine differences between the recently implemented integrated spiral (year 1) and conventional block (years 2-4) MD curriculum at University of British Columbia (UBC) with respect to knowledge of concussion diagnosis and management. Design Cross-sectional survey Setting UBC undergraduate MD program Participants An online survey was distributed to all 1152 students currently enrolled in UBC medical school. To date, 123 surveys have been returned (10.7% response rate) with 58 first year students (integrated spiral curriculum) and 65 students in years 2-4 (conventional block curriculum). Females made up 60% of responses. Interventions Online survey, hosted by FluidSurveys (Fluidware, Ottawa, ON), distributed through email. Outcome measures Questions focused on demographic data, knowledge of concussion definitions, and management considerations. Main results Majority of responses revealed both curriculums have promoted a strong understanding of concussion definition and related symptoms (84% correct response rate). Only 8.1% of participants believed that functional imaging (MRI or CT) is a mandatory assessment tool for concussions. Differences between the conventional and integrated curriculums included: understanding concussions can occur without direct impact to the head (91.4% integrated vs. 69.2% conventional: χ2(1)=43.325, p Conclusions The findings from this study reveal a number of positive signs regarding the evolution of medical education in terms of concussion diagnosis and management. The integrated curriculum is taking further steps in advancing concussion knowledge in medical education. Competing interests None.

In this study, two experiments were devised to examine the control strategy used by individuals when performing sequential aiming movements. Of particular interest was the aiming behavior displayed when task difficulty was changed midway through a sequence of movements. In Experiment 1, target size was manipulated, as the targets were made either larger or smaller, between the 8th and 12th movement of the sequence. In Experiment 2, the amplitude between the two targets was similarly changed while the target size remained constant. Results revealed that in Experiment 1, individuals took two movements following the perturbation to target size, to re-tune their movement times in order to correspond with the new task difficulty. Conversely for Experiment 2, movement time changed immediately and in correspondence with the new target amplitude. These findings demonstrate that participants can use information from the preceding movement to prepare and guide subsequent movements--but only when target size is changed. When response amplitude changes mid-sequence, it seems individuals rely more on immediate, target-derived information. Therefore, counter to some current accounts of visual movement control, it appears that memory representations of the preceding movement can guide subsequent movements; however, this information appears selectively accessed in a context-dependent fashion.

There is considerable utility in the use of transcranial Doppler ultrasound (TCD) to assess cerebrovascular function. The brain is unique in its high energy and oxygen demand but limited capacity for energy storage that necessitates an effective means of regional blood delivery. The relative low cost, ease-of-use, non-invasiveness, and excellent temporal resolution of TCD make it an ideal tool for the examination of cerebrovascular function in both research and clinical settings. TCD is an efficient tool to access blood velocities within the cerebral vessels, cerebral autoregulation, cerebrovascular reactivity to CO2, and neurovascular coupling, in both physiological states and in pathological conditions such as stroke and head trauma. In this review, we provide: (1) an overview of TCD methodology with respect to other techniques; (2) a methodological synopsis of the cerebrovascular exam using TCD; (3) an overview of the physiological mechanisms involved in regulation of the cerebral blood flow; (4) the utility of TCD for assessment of cerebrovascular pathology; and (5) recommendations for the assessment of four critical and complimentary aspects of cerebrovascular function: intra-cranial blood flow velocity, cerebral autoregulation, cerebral reactivity, and neurovascular coupling. The integration of these regulatory mechanisms from an integrated systems perspective is discussed, and future research directions are explored.

Of 3 patients undergoing drive-line ID he developed a pseudoaneurysm that was emergently surgically treated. The 26 patients with drive-line infection who were treated medically required multiple re-admissions due to worsening drainage. Two of these were admitted in septic shock and were considered not surgical candidates. Ultimately, they succumbed to their infections. Eight of them underwent heart transplantation; 5 had positive intra-operative pump-pocket cultures. Twenty medically treated patients are still alive. Thus, despite improved survival associated with LVAD therapy, infection continues to be a major limiting factor. We believe that surgery should typically be reserved for stable medically intractable infections or patients who present with septic emboli. Pump or pump-pocket infection can be treated with pump exchange or intra-abdominal relocation. Drive-lines should be unroofed to prevent component seeding. Infected pump and pockets should be widely debrided and pumps relocated to prevent them from re-infection. Despite these results, the best alternative to avoid recurrence of LVAD-associated infection appears to be removal of the pump. Therefore, it is imperative that, when device exchange or relocation is contemplated, a thorough work-up be undertaken to prove the patient has not recovered. We currently use a work-up similar to that described by Birks and colleagues. If the patient has recovered, then the decision is made to attempt to explant the device.

The effect that cardiorespiratory fitness has on the dynamic cerebral autoregulatory capacity during changes in mean arterial pressure (MAP) remains equivocal. Using a multiple-metrics approach, challenging MAP across the spectrum of physiological extremes (i.e. spontaneous through forced MAP oscillations), we characterized dynamic cerebral autoregulatory capacity in 19 male endurance athletes and 8 controls via three methods: [1] onset of regulation (i.e., time delay before an increase in middle cerebral artery (MCA) conductance [MCA flow velocity (MCAv)/mean arterial pressure (MAP)] and rate of regulation, after transient hypotension induced by sit-to-stand, and transfer function analysis (TFA) of MAP and MCAv responses during [2] spontaneous and [3] forced oscillations (5-min of squat-stand maneuvers performed at 0.05 and 0.10 Hz). Reductions in MAP and mean MCAv (MCAVmean) during initial orthostatic stress (0-30 s after sit-to-stand) and the prevalence of orthostatic hypotension were also determined. Onset of regulation was delayed after sit-to-stand in athletes (3.1±1.7 vs. 1.5±1.0 s; p=0.03), but rate of regulation was not different between groups (0.24±0.05 vs. 0.21±0.09 s-1; p=0.82). While both groups had comparable TFA metrics during spontaneous oscillations, athletes had higher TFA gain during 0.10 Hz squat-stand vs. recreational controls (p=0.01). Reductions in MAP (p=0.15) and MCAVmean (p=0.11) during orthostatic stress and the prevalence of initial orthostatic hypotension (p=0.65) were comparable between groups. These results indicate an intact ability of the cerebral vasculature to react to spontaneous oscillations but an attenuated capability to counter rapid and large changes in MAP in individuals with elevated cardiorespiratory fitness.New findingsWhat is the central question of this study?What is the impact of cardiorespiratory fitness on dynamic cerebral autoregulatory capacity?What is the main finding and its importance?Our results indicate an intact ability of the cerebral vasculature to react to spontaneous oscillations but an attenuated capability to counter rapid and large changes in mean arterial pressure in individuals with elevated cardiorespiratory fitness.

Objective To examine how a season of sub-concussive head-impact exposures influence a measure of response-inhibition in contact-sport athletes. Design Prospective cohort Setting Laboratory Participants Twenty-five contact-sport athletes (20.3±1.3 years) performed a response-inhibition task prior to and following the competitive season. Each player wore an adhesive accelerometer (X2Biosystems) during games. Players were excluded if they sustained a concussion during the season. Interventions To probe response-inhibition, an object hit-and-avoid sensorimotor task (KINARM) was performed. This 2.5 minute task entailed the successful hitting of two target shapes while avoiding six other distractor shapes. Players were divided into tertiles (high, medium, low; n=8) based on cumulative number of 20g+ head impacts, cumulative peak linear acceleration (cPLA), and cumulative peak rotational acceleration (cPRA). Comparisons of response-inhibition performance were made between high and low tertiles. Outcome measures Pre-post changes in number of targets hit, distractors hit, total cancelled movements towards pursued distractors (CPDs), and total task accuracy (percent) were recorded for the KINARM task. Results Independent t-tests indicated no significant differences between the high and low tertiles on the KINARM task despite the high tertile group experiencing 4-times greater head impacts throughout the season. There was a trend for greater KINARM task improvement from pre-to-post-season in the bottom tertile, as reflected by the increase in CPDs in their post-season measures (cumulative number: p=0.06, CI=[−16.2148519, 0.7148519]). Conclusions These findings reveal that one season of repetitive sport-related head impacts does not appear to have a significant effect on an athlete’s ability to inhibit a motor response. Competing interests All authors have no competing interests to declare.