Transcranial Doppler Ultrasound and Concussion-Supplemental Symptoms with Physiology: A Systematic Review.

Sport-related concussion (SRC) can impair the cerebrovasculature both acutely and chronically. Transcranial Doppler (TCD) ultrasound assessment has the potential to illuminate the mechanisms of impairment and provide an objective evaluation of SRC. The current systematic review investigated studies employing TCD ultrasound assessment of intracranial arteries across three broad categories of cerebrovascular regulation: neurovascular coupling (NVC), cerebrovascular reactivity (CVR), and dynamic cerebral autoregulation (dCA). The current review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (CRD42021275627). The search strategy was applied to PubMed, as this database indexes all biomedical journals. Original articles on TCD for athletes with medically diagnosed SRC were included. Title/abstract and full-text screening were completed by three authors. Two authors completed data extraction and risk of bias using the Methodological Index for Non-Randomized Studies and Scottish Intercollegiate Guideline Network checklists. Of the 141 articles identified, 14 met the eligibility criteria. One article used an NVC challenge, eight assessed CVR, and six investigated dCA. Methodologies varied widely among studies, and results were heterogeneous. There was evidence of cerebrovascular impairment in all three domains roughly 2 days post-SRC, but the magnitude and recovery of these impairments were not clear. There was evidence that clinical symptom resolution occurred before cerebrovascular function, indicating that physiological deficits may persist despite clinical recovery and return to play. Collectively, this emphasizes an opportunity for the use of TCD to illuminate the cerebrovascular deficits caused by SRC. It also highlights that there is need for consistent methodological rigor when employing TCD in a SRC population.

Adolescent Sport-Related Concussion and the Associated Neurophysiological Changes: A Systematic Review.

BACKGROUND: Sport-related concussion (SRC) has been shown to induce cerebral neurophysiological deficits, quantifiable with electroencephalography (EEG). As the adolescent brain is undergoing rapid neurodevelopment, it is fundamental to understand both the short- and long-term ramifications SRC may have on neuronal functioning. The current systematic review sought to amalgamate the literature regarding both acute/subacute (≤28 days) and chronic (>28 days) effects of SRC in adolescents via EEG and the diagnostic accuracy of this tool. METHODS: The review was registered within the Prospero database (CRD42021275256). Search strategies were created and input into the PubMed database, where three authors completed all screening. Risk of bias assessments were completed using the Scottish Intercollegiate Guideline Network and Methodological Index for Non-Randomized Studies. RESULTS: A total of 128 articles were identified; however, only seven satisfied all inclusion criteria. The studies ranged from 2012 to 2021 and included sample sizes of 21 to 81 participants, albeit only ∼14% of the included athletes were females. The studies displayed low-to-high levels of bias due to the small sample sizes and preliminary nature of most investigations. Although heterogeneous methods, tasks, and analytical techniques were used, 86% of the studies found differences compared with control athletes, in both the symptomatic and asymptomatic phases of SRC. One study used raw EEG data as a diagnostic indicator demonstrating promise; however, more research and standardization are a necessity. CONCLUSIONS: Collectively, the findings highlight the utility of EEG in assessing adolescent SRC; however, future studies should consider important covariates including biological sex, maturation status, and development.

Comparison of the Buffalo Concussion Treadmill Test With a Physiologically Informed Cycle Test: Calgary Concussion Cycle Test.

BACKGROUND: Sport-related concussions are a complex injury requiring multifaceted assessment, including physical exertion. Currently, concussion testing relies primarily on a treadmill-based protocol for assessing exertion-related symptoms in persons after concussion. This study compared a modified cycle protocol (Calgary Concussion Cycle Test [CCCT]) with the clinically adopted standard, the Buffalo Concussion Treadmill Test (BCTT), across multiple physiological parameters. HYPOTHESIS: Treadmill and cycle matched workload protocols would produce similar results for cerebral blood velocity, mean arterial pressure (MAP), and end-tidal carbon dioxide partial pressure (PETCO2), but heart rate (HR) and oxygen consumption (VO2) would be higher on the treadmill than the cycle modality. STUDY DESIGN: Crossover study design. LEVEL OF EVIDENCE: Level 3. METHODS: A total of 17 healthy adults (8 men, 9 women; age, 26 ± 3 years; body mass index, 23.8 ± 2.7 kg/m2) completed the BCTT and CCCT protocols, 7 days apart in a randomized order. During both exertional protocols, the physiological parameters measured were middle cerebral artery mean blood velocity (MCAv), MAP, PETCO2, VO2, and HR. Analysis of variance with effect size computations, coefficient of variation, and Bland-Altman plots with 95% limits of agreement were used to compare exercise tests. RESULTS: The BCTT and CCCT produced comparable results for both male and female participants with no significant differences for average MCAv, MAP, and PETCO2 (all P > 0.05; all generalized eta squared [η2G] < 0.02 [negligible]; P value range, 0.29-0.99) between stages. When accounting for exercise stage and modality, VO2 (P < 0.01) and HR (P < 0.01) were higher on the treadmill compared with the cycle. Aside from the final few stages, all physiology measures displayed good-to-excellent agreeability/variability. CONCLUSION: The CCCT was physiologically similar to the BCTT in terms of MCAv, PETCO2, and MAP; however, HR and VO2 differed between modalities. CLINICAL RELEVANCE: Providing a cycle-based modality to exertional testing after injury mayincrease accessibility to determine symptom thresholds in the future.

Influence of sex on the reliability of cerebral blood velocity regulation during lower body negative pressure and supine cycling with considerations of the menstrual cycle.

Objective.To evaluate sex differences in the reliability of absolute and relative cerebral blood velocity (CBv) during concurrent supine cycling with lower body negative pressure (LBNP).Approach. A total of 19 participants (11 females; aged 20-33 years) completed five testing sessions, occurring on 7 d intervals. Visit 1 was a maximal-ramp-cycle test to ascertain peak CBv wattage. During visits 2-5, supine cycling protocol occurred at individualized peak CBv wattages with progressive decreases in LBNP from 0 to -20, -40, -60, -70, and -80 Torr. Menstrual cycle day was self-reported via the Rhinessa Women's Questionnaire. Transcranial Doppler ultrasound insonated bilateral middle cerebral artery velocity (MCAv). Two-way ANOVA assessed potential day- and sex-differences at each LBNP stage. Reliability was determined using intraclass correlation coefficients (ICC) and coefficient of variation (CoV).Main results. For all physiological measures, no main-effects were present for day- or interaction-terms (p> 0.067; negligible-to-small effect sizes), while sex differences were noted for MCAv, blood pressure, and heart rate (p< 0.046). Across visits, males and females displayed excellent and good-to-excellent levels of reliability for MCAv metrics, respectively (ICC range: 0.745-0.999; CoV range: 0.33%-9.90%).Significance. During the current investigation, both relative and absolute CBv demonstrated high reliability in both male and female participants during a supine LBNP cycling protocol. An exploratory analysis revealed increased variance was found in female participants dependent on contraceptive use. Despite this, results indicate future LBNP studies may include females at any menstrual cycle stage.

Prevention strategies and modifiable risk factors for sport-related concussions and head impacts: a systematic review and meta-analysis.

OBJECTIVES: To evaluate prevention strategies, their unintended consequences and modifiable risk factors for sport-related concussion (SRC) and/or head impact risk. DESIGN: This systematic review and meta-analysis was registered on PROSPERO (CRD42019152982) and conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. DATA SOURCES: Eight databases (MEDLINE, CINAHL, APA PsycINFO, Cochrane (Systematic Review and Controlled Trails Registry), SPORTDiscus, EMBASE, ERIC0 were searched in October 2019 and updated in March 2022, and references searched from any identified systematic review. ELIGIBILITY CRITERIA: Study inclusion criteria were as follows: (1) original data human research studies, (2) investigated SRC or head impacts, (3) evaluated an SRC prevention intervention, unintended consequence or modifiable risk factor, (4) participants competing in any sport, (5) analytic study design, (6) systematic reviews and meta-analyses were included to identify original data manuscripts in reference search and (7) peer-reviewed. Exclusion criteria were as follows: (1) review articles, pre-experimental, ecological, case series or case studies and (2) not written in English. RESULTS: In total, 220 studies were eligible for inclusion and 192 studies were included in the results based on methodological criteria as assessed through the Scottish Intercollegiate Guidelines Network high ('++') or acceptable ('+') quality. Evidence was available examining protective gear (eg, helmets, headgear, mouthguards) (n=39), policy and rule changes (n=38), training strategies (n=34), SRC management strategies (n=12), unintended consequences (n=5) and modifiable risk factors (n=64). Meta-analyses demonstrated a protective effect of mouthguards in collision sports (incidence rate ratio, IRR 0.74; 95% CI 0.64 to 0.89). Policy disallowing bodychecking in child and adolescent ice hockey was associated with a 58% lower concussion rate compared with bodychecking leagues (IRR 0.42; 95% CI 0.33 to 0.53), and evidence supports no unintended injury consequences of policy disallowing bodychecking. In American football, strategies limiting contact in practices were associated with a 64% lower practice-related concussion rate (IRR 0.36; 95% CI 0.16 to 0.80). Some evidence also supports up to 60% lower concussion rates with implementation of a neuromuscular training warm-up programme in rugby. More research examining potentially modifiable risk factors (eg, neck strength, optimal tackle technique) are needed to inform concussion prevention strategies. CONCLUSIONS: Policy and rule modifications, personal protective equipment, and neuromuscular training strategies may help to prevent SRC. PROSPERO REGISTRATION NUMBER: CRD42019152982.

The effect of supine cycling and progressive lower body negative pressure on cerebral blood velocity responses.

Moderate-intensity aerobic exercise increases cerebral blood velocity (CBv) primarily due to hyperpnea-induced vasodilation; however, the integrative control of cerebral blood flow (CBF) allows other factors to contribute to the vasodilation. Although lower body negative pressure (LBNP) can reduce CBv, the exact LBNP intensity required to blunt the aforementioned exercise-induced CBv response is unknown. This could hold utility for concussion recovery, allowing individuals to exercise at higher intensities without symptom exacerbation. Thirty-two healthy adults (age: 20-33 yr; 19 females/13 males) completed a stepwise maximal exercise test during a first visit to determine each participant's wattage associated with their exercise-induced maximal CBv increase. During the second visit, following supine rest, participants completed moderate-intensity exercise at their determined threshold, while progressive LBNP was applied at 0, -20, -40, -60, -70, -80, and ∼88 Torr. Bilateral middle cerebral artery blood velocities (MCAvs), mean arterial pressure (MAP), heart rate, respiratory rate, and end-tidal carbon dioxide levels were measured continuously. Two-way analysis of variance with effect sizes compared between sexes and stages. Compared with resting supine baseline, averaged MCAv was elevated during 0 and -20 Torr LBNP (q value > 7.73; P < 0.001); however, no differences were noted between baseline and -40 to -70 Torr (q value < |4.24|; P > 0.262). Differences were present between females and males for absolute MCAv measures (q value > 11.2; P < 0.001), but not when normalized to baseline (q value < 0.03; P > 0.951). Supine cycling-elicited increases in MCAv are able to be blunted during the application of LBNP ranging from -40 to -70 Torr. The blunted CBv response demonstrates the potential benefit of allowing individuals to aerobically train (moderate-intensity supine cycling with LBNP) without exacerbating symptoms during the concussion recovery phase.NEW & NOTEWORTHY The current investigation demonstrated that moderate-intensity supine cycling-induced increases in cerebral blood velocities were balanced by the lower body negative pressure-induced decreases in cerebral blood velocity. Although performed in a healthy population, the results may lend themselves to a potential treatment option for individuals recovering from concussion or experience persistent concussion symptoms.

The Effect of Physical Exertional Testing on Postconcussion Symptom Scale Scores in Male and Female High School Students.

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.

Physical activity following sport-related concussion in adolescents: a systematic review.

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 (<18 yr). Participants were seen within 1-2 wk after SRC for acute studies and 4 wk after SRC for studies focused on prolonged recoveries, which are standard timelines across the literature. Twenty-two studies met the inclusion criteria [i.e., 8 regarding physical activity (PA-daily aerobic activity including light and moderate intensities), 8 evaluating active rehabilitation/exercise programs (20 min of daily aerobic exercise below symptom threshold), 6 examining a single bout of exertion]. The methodological quality of the literature was assessed using the Downs and Black risk of bias (ROB) checklist. The ROB scores ranged from 7 to 24, with only two randomized controlled trials included. Studies demonstrated that single bouts of exertion testing were safe and feasible. Daily PA or active rehabilitation/exercise programs led to a reduction in symptoms present and a decrease in number of days to medical clearance. Following a brief period of rest (24-48 h), individuals may gradually and safely return to PA below their physical symptom exacerbation thresholds. Further research is warranted to delineate how to optimize the timing, intensity, duration, and modality of PA impacts symptom resolution and physiological recovery following different subtypes of SRC.

Concurrent Validity of a Stationary Cycling Test and the Buffalo Concussion Treadmill Test in Adults With Concussion.

CONTEXT: After concussion, a multifaceted assessment is recommended, including tests of physical exertion. The current criterion standard for exercise testing after concussion is the Buffalo Concussion Treadmill Test (BCTT); however, validated tests that use alternative exercise modalities are lacking. OBJECTIVE: To evaluate the feasibility and concurrent validity of a universal cycling test of exertion compared with the BCTT in adults who sustained a sport-related concussion. DESIGN: Crossover study. SETTING: University sports medicine clinic. PATIENTS OR OTHER PARTICIPANTS: Twenty adults (age = 18-60 years) diagnosed with a sport-related concussion. INTERVENTION(S): Participants completed the BCTT and a cycling test of exertion in random order, approximately 48 hours apart. MAIN OUTCOME MEASURE(S): The primary outcome of interest was maximum heart rate (HRmax; beats per minute [bpm]). Secondary outcomes of interest were the total number of symptoms endorsed on the Post-Concussion Symptom Scale, whether the participant reached volitional fatigue (yes or no), the symptom responsible for test cessation (Post-Concussion Symptom Scale), maximum rating of perceived exertion, symptom severity on a visual scale (0-10), and the time to test cessation. RESULTS: Of the 20 participants, 19 (10 males, 9 females) completed both tests. One participant did not return for the second test and was excluded from the analysis. No adverse events were reported. The median HRmax for the BCTT (171 bpm; interquartile range = 139-184 bpm) was not different from the median HRmax for the cycle (173 bpm; interquartile range = 160-182 bpm; z = -0.63; P = .53). For both tests, the 3 most frequently reported symptoms responsible for test cessation were headache, dizziness, and pressure in the head. Of interest, most participants (64%) reported a different symptom responsible for cessation of each test. CONCLUSIONS: On the novel cycling test of exertion, participants achieved similar HRmax and test durations and, therefore, this test may be a suitable alternative to the BCTT. Future research to understand the physiological reason for the heterogeneity in symptoms responsible for test cessation is warranted.

Long-term heart transplant recipients: heart rate-related effects on augmented transfer function coherence during repeated squat-stand maneuvers in males.

Previous research has highlighted that squat-stand maneuvers (SSMs) augment coherence values within the cerebral pressure-flow relationship to ∼0.99. However, it is not fully elucidated if mean arterial pressure (MAP) leads to this physiological entrainment independently, or if heart rate (HR) and/or the partial pressure of carbon dioxide (Pco2) also have contributing influences. A 2:1 control-to-case model was used in the present investigation [participant number (n) = 40; n = 16 age-matched (AM); n = 16 donor control (DM); n = 8 heart transplant recipients (HTRs)]. The latter group was used to mechanistically isolate the extent to which HR influences the cerebral pressure-flow relationship. Participants completed 5 min of squat-stand maneuvers at 0.05 Hz (10 s) and 0.10 Hz (5 s). Linear transfer function analysis (TFA) examined the relationship between different physiological inputs (i.e., MAP, HR, and Pco2) and output [cerebral blood velocity (CBV)] during SSM; and cardiac baroreceptor sensitivity (BRS). Compared with DM, cardiac BRS was reduced in AM (P < 0.001), which was further reduced in HTR (P < 0.045). In addition, during the SSM, HR was elevated in HTR compared with both control groups (P < 0.001), but all groups had near-maximal coherence metrics ≥0.98 at 0.05 Hz and ≥0.99 at 0.10 Hz (P ≥ 0.399). In contrast, the mean HR-CBV/Pco2-CBV relationships ranged from 0.38 (HTR) to 0.81 (DM). Despite near abolishment of BRS and blunted HR following heart transplantation, long-term HTR exhibited near-maximal coherence within the MAP-CBV relationship, comparable with AM and DM. Therefore, these results show that the augmented coherence with SSM is driven by blood pressure, whereas elevations in TFA coherence as a result of HR contribution are likely correlational in nature.

Does task complexity impact the neurovascular coupling response similarly between males and females?

BACKGROUND: While previous studies have demonstrated a complex visual scene search elicits a robust neurovascular coupling (NVC) response, it is unknown how the duration of visual stimuli presentation influences NVC metrics. This study examined how stimuli duration, in addition to biological sex and self-reported engagement impact NVC responses. METHODS: Participants (n = 20, female = 10) completed four visual paradigms. Three involved simple visual shapes presented at 0.5-, 2-, and 4-s intervals in randomized orders. The fourth paradigm was a complex visual scene search ("Where's Waldo?"). Participants completed eight cycles of 20-s eyes-closed followed by 40-s eyes-open. Transcranial Doppler ultrasound indexed posterior and middle cerebral artery velocities (PCA and MCA). Participants self-reported their engagement following each task (1 [minimal] to 10 [maximal]). RESULTS: The "Where's Waldo?" task evoked greater PCA percent increase (all p < 0.001) and area under the curve during the first 30-s of the task (all p < 0.001) compared to simple shapes. Females displayed greater absolute baseline and peak PCA and MCA velocities across all tasks (all p < 0.002). Subjective engagement displayed moderate correlation levels with PCA percent increase (Spearman ρ = 0.58) and area under the curve (Spearman ρ = 0.60) metrics in males, whereas these were weak for females (Spearman ρ = 0.43 and ρ = 0.38, respectively). CONCLUSIONS: The complex visual paradigm "Where's Waldo?" greatly augmented the signal-to-noise ratio within the PCA aspects of the NVC response compared to simple shapes. While both sexes had similar NVC responses, task engagement was more related to NVC metrics in males compared to females. Therefore, future NVC investigations should consider task engagement when designing studies.

The validity and reliability of ultra-short-term heart rate variability parameters and the influence of physiological covariates.

Ultra-short-term (UST) heart rate variability (HRV) metrics have increasingly been proposed as surrogates for short-term HRV metrics. However, the concurrent validity, within-day reliability, and between-day reliability of UST HRV have yet to be comprehensively documented. Thirty-six adults (18 males, age: 26 ± 5 yr, BMI: 24 ± 3 kg/m2) were recruited. Measures of HRV were quantified in a quiet-stance upright orthostatic position via three-lead electrocardiogram (ADInstruments, FE232 BioAmp). All short-term data recordings were 300 s in length and five UST time points (i.e., 30 s, 60 s, 120 s, 180 s, and 240 s) were extracted from the original 300-s recording. Bland-Altman plots with 95% limits of agreement, repeated measures ANOVA and two-tailed paired t tests demarcated differences between UST and short-term recordings. Linear regressions, coefficient of variation, intraclass correlation coefficients, and other tests examined the validity and reliability in both time- and frequency domains. No group differences were noted between all short-term and UST measures, for either time- (all P > 0.202) or frequency-domain metrics (all P > 0.086). A longer recording duration was associated with augmented validity and reliability, which was less impacted by confounding influences from physiological variables (e.g., respiration rate, carbon dioxide end-tidals, and blood pressure). Conclusively, heart rate, time-domain, and relative frequency-domain HRV metrics were acceptable with recordings greater or equal to 60 s, 240 s, and 300 s, respectively. Future studies employing UST HRV metrics should thoroughly understand the methodological requirements to obtain accurate results. Moreover, a conservative approach should be utilized regarding the minimum acceptable recording duration, which ensures valid/reliable HRV estimates are obtained.NEW & NOTEWORTHY 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).

What recording duration is required to provide physiologically valid and reliable dynamic cerebral autoregulation transfer functional analysis estimates?

Objective. Currently, a recording of 300 s is recommended to obtain accurate dynamic cerebral autoregulation estimates using transfer function analysis (TFA). Therefore, this investigation sought to explore the concurrent validity and the within- and between-day reliability of TFA estimates derived from shorter recording durations from squat-stand maneuvers.Approach. Retrospective analyses were performed on 70 young, recreationally active or endurance-trained participants (17 females; age: 26 ± 5 years, [range: 20-39 years]; body mass index: 24 ± 3 kg m-2). Participants performed 300 s of squat-stands at frequencies of 0.05 and 0.10 Hz, where shorter recordings of 60, 120, 180, and 240 s were extracted. Continuous transcranial Doppler ultrasound recordings were taken within the middle and posterior cerebral arteries. Coherence, phase, gain, and normalized gain metrics were derived. Bland-Altman plots with 95% limits of agreement (LOA), repeated measures ANOVA's, two-tailed paired t-tests, coefficient of variation, Cronbach's alpha, intraclass correlation coefficients, and linear regressions were conducted.Main results. When examining the concurrent validity across different recording durations, group differences were noted within coherence (F(4155) > 11.6,p < 0.001) but not phase (F(4155) < 0.27,p > 0.611), gain (F(4155) < 0.61,p > 0.440), or normalized gain (F(4155) < 0.85,p > 0.359) parameters. The Bland-Altman 95% LOA measuring the concurrent validity, trended to narrow as recording duration increased (60 s: < ±0.4, 120 s: < ±0.3, 180 s  < ±0.3, 240 s: < ±0.1). The validity of the 180 and 240 s recordings further increased when physiological covariates were included within regression models.Significance. Future studies examining autoregulation should seek to have participants perform 300 s of squat-stand maneuvers. However, valid and reliable TFA estimates can be drawn from 240 s or 180 s recordings if physiological covariates are controlled.

A Standardized Buffalo Concussion Treadmill Test Following Sport-Related Concussion in Youth: Do ActiGraph Algorithms Matter?

CONTEXT: Current recovery guidelines following sport-related concussion (SRC) include 24-48 hours of rest followed by gradual return-to-activity with heart rate (HR) maintained below symptom threshold. Additionally, the monitoring of physical activity (PA) post-SRC using ActiGraph accelerometers can provide further objective insight on amounts of activity associated with recovery trajectories. Cut-point algorithms for these devices allow minute-by-minute PA to be classified into intensity domains; however, studies have shown different algorithms employed on the same healthy participant dataset can produce varying classifications. OBJECTIVE: To identify the most physiologically appropriate cut-point algorithm (Evenson or Romanzini) to analyze ActiGraph data in concussed youth with comparisons to HR response on the Buffalo Concussion Treadmill Test (BCTT). DESIGN: Prospective cohort study. SETTING: Sport-concussion clinic within a university setting. PATIENTS OR OTHER PARTICIPANTS: Eleven high-school students (5 male, 6 female; median [range] age =16 years [15-17], height = 177.8 cm [157.5-198.1], weight = 67 kg [52-98], body mass index = 22 kg/m2 [17-31]) involved in high-risk sport who sustained a physician diagnosed SRC. MAIN OUTCOME MEASURE(S): Evenson and Romanzini algorithm PA intensity domains via ActiGraph data and HR during the BCTT. RESULTS: There were differences in moderate (P = .001) and vigorous (P = .002) intensities between algorithms, but no difference in light (P = .548). Evenson classified most of the time as moderate intensity (57.03% [0.00-94.12%]), whereas Romanzini classified virtually all PA as vigorous (88.25% [2.94-97.06%]). PA based on HR (stages 1-7: 20-39% HR reserve (HRR), stages 8-13: 40-59% HRR, stages 14 and above: 60-85% HRR) indicated the BCTT primarily involves light-to-moderate intensity, and therefore is better represented by the Evenson algorithm. CONCLUSIONS: The Evenson algorithm better characterizes the HR response during a standardized exercise test in concussed individuals and therefore should be used to analyze ActiGraph PA data in a concussed paediatric population.

Changes in exertion-related symptoms in adults and youth who have sustained a sport-related concussion.

OBJECTIVES: To identify the symptoms responsible for cessation of exercise testing and evaluate changes in post-concussion symptom scores on the Post-Concussion Symptom Scale (PCSS) from the Sport-Concussion Assessment Tool (SCAT5) immediately, 1-4h, and 6-12h following completion of the Buffalo Concussion Treadmill Test (BCTT) in youth and adults who have sustained a sport-related concussion. DESIGN: Prospective case-series. METHODS: Individuals who were diagnosed with a sport-related concussion and self-reported difficulties with exertion were referred to perform an exertional treadmill test. Individuals were recruited from a university sports medicine clinic. Change in PCSS symptom severity scores were operationally defined as a change ≥4 points. RESULTS: Forty-five individuals aged 13-57 years consented to participate. A total of 14/24 (58.3%) female and 13/21 (61.9%) male participants reported an increase in symptom severity scores immediately following the BCTT. At 1-4h, 5/10 (50.0%) males and 5/14 (35.7%) females who completed the PCSS had elevated symptom severity scores compared to pre-exertion. Only 24.2% (3/17 males and 5/16 females) of participants completing the PCSS at 6-12h reported increased symptom severity scores. CONCLUSION: Exertional testing is an important component of a multifaceted assessment following concussion; however, previous research evaluating symptom responses to exertion is limited. This study provides evidence to suggest individuals who experience an exacerbation of concussion-associated symptoms after exertion are likely to return to pre-exertion levels within the same day. Future research monitoring symptoms following exertion and throughout recovery should be performed in tandem with physiological measures to better understand the source of symptoms.

Baseline Performance of High School Rugby Players on the Sport Concussion Assessment Tool 5.

CONTEXT: Version 5 of the Sport Concussion Assessment Tool (SCAT5) was released in 2017 with an additional 10-word list option in the memory section and additional instructions for completing the symptom scale. OBJECTIVE: To provide reference scores for high school rugby union players on the SCAT5, including immediate memory using the 10-word list, and examine how age, sex, and concussion history affected performance. DESIGN: Cross-sectional study. SETTING: Calgary, Alberta high schools. PATIENTS OR OTHER PARTICIPANTS: High school rugby union players (ages 15-18 years) participating in a 2018 season cohort study (n = 380, males = 210, females = 170). MAIN OUTCOME MEASURE(S): Sport Concussion Assessment Tool 5 scores, including total number of symptoms (of 20), symptom severity (of 132), 10-word immediate memory (of 30), delayed memory (of 10), modified Standardized Assessment of Concussion (of 50), and balance examination (of 30). RESULTS: The median number of symptoms reported at baseline ranged from 5 to 8 across sex and age stratifications. Median symptom severity was lowest in males with no concussion history (7; range, 0-28) and highest in females with a concussion history (13, range = 0-45). Median total scores on immediate memory were 2-3 (range = 0-4) for males and 21 (range = 9-29) for females. Median total scores were 3 (range = 0-4) on digits backward and 7 (range = 0-20) on delayed memory (all groups). Based on simultaneous quantile (q) regression at 0.50 and 0.75, adjusted for age and concussion history, being female was associated with a higher total symptoms score (q0.75 ßfemale = 2.85; 99% confidence interval [CI] = 0.33, 5.37), higher total symptom severity score (q0.75 ßfemale = 8.00; 99% CI = 2.83, 13.17), and lower number of errors on the balance examination (q0.75 ßfemale = -3.00; 99% CI = -4.85, -1.15). Age and concussion history were not associated with any summary measures. CONCLUSIONS: The 10-word list option in the memory section reduced the likelihood of a ceiling effect. A player's sex may be an important consideration when interpreting the SCAT5 after concussion.

Carbohydrate-restricted Diet and High-intensity Interval Training Exercise Improve Cardio-metabolic and Inflammatory Profiles in Metabolic Syndrome: A Randomized Crossover Trial.

Introduction One approach to slow the pandemic of obesity and chronic disease is to look to our evolutionary past for clues of the changing behaviors contributing to the emergence of 'diseases of civilization'. Modern humans have deviated from the lifestyle behaviors of our ancestors that have introduced pressures (i.e. diet and activity changes) quicker than our genetic ability to respond. This caused a 'mismatch' between our biological systems and environment, leading to 'man-made' chronic diseases. Purpose The purpose of the study was to investigate the effects of a short-term evolutionarily informed dietary and lifestyle intervention on inflammatory and cardio-metabolic profiles in individuals characterized as having metabolic syndrome (MetS). Methods Twelve subjects with MetS followed a crossover design with two, four-week interventions, including a carbohydrate (CHO)-restricted Paleolithic-based diet (CRPD; <50g CHO) with sedentary activity (CRPD-Sed) and CRPD with high-intensity interval training (CRPD-Ex), separated by a four-week washout period. The HIIT exercise consisted of 10 X 60 seconds (s) cycling intervals interspersed with 60s of active recovery three d/wk for four weeks. The effects of a diet with sedentary activity as compared to a diet with exercise on body composition, as well as the cardiovascular, inflammatory, and metabolic profiles, were assessed. A two-way analysis of variance (ANOVA) with repeated measures was performed with a post-hoc analysis using a simple effects analysis with a Bonferroni adjustment. The level of statistical significance was established a priori as p < 0.05. Results Compared to baselines, CRPD-Sed and CRPD-Ex improved cardio-metabolic markers, including reductions in waist adiposity (-15%, -18%), body mass (-3%, -5%), body fat % (BF%; -7%, -12%), fasting plasma glucose (GLU; -20%, -27%), triglycerides (TG; -47%, -52%), fasting insulin (-34%, -39%), insulin resistance (-35%, -46%), and increased HDL-C (+22%, +36%) and VO2max (+22% and +29%), respectively. CRPD-Sed and CRPD-Ex also reduced inflammatory markers, including hsCRP (-32% and-36%), TNF-alpha (-35% and -41%), IL-6 (-29% and -40%), and ICAM-1 (-19%, -23%), respectively, when compared to baseline. Conclusion Adopting behaviors from our evolutionary past, including diet and exercise, shows favorable cardio-metabolic and inflammatory profiles in those individuals characterized with MetS.

Carbohydrate-restricted Diet and Exercise Increase Brain-derived Neurotrophic Factor and Cognitive Function: A Randomized Crossover Trial.

Introduction Metabolic syndrome (MetS) has been recognized as one of the most important clinical challenges and global health issues of today. Growing evidence suggests that mechanisms of energy metabolism may also play a key role in mediating aspects of cognitive function. Brain-derived neurotrophic factor (BDNF) is one such factor well known for its critical role in neuronal plasticity, including memory and learning, and more recently metabolic processes. BDNF levels have been shown separately to be dependent on diet and exercise programming. Purpose The purpose of this study was to investigate the effect of diet and exercise on BDNF levels and cognitive functioning with any metabolic association in individuals characterized with MetS. Methods Twelve subjects with MetS followed a randomized crossover design with two four-week interventions, including a carbohydrate (CHO)-restricted Paleolithic-based diet (CRPD; <50gCHO) with sedentary activity (CRPD-Sed) and CRPD with high intensity interval training (HIIT; CRPD-Sed), separated by a four-week washout period. The HIIT exercise consisted of 10 x 60 s cycling intervals interspersed with 60 s of active recovery 3 day/week for four-week. Serum BDNF was detected and quantified via enzyme-linked immunosorbent assay (ELISA). Cognitive executive function (Stroop Test) and self-perceived cognitive symptoms and function (MOS-CFS) were quantified. A two-way analysis of variance with repeated measures was performed with post-hoc analysis using simple effects analysis with a Bonferroni adjustment. The level of statistical significance was established a priori as P < 0.05. Results Compared to baseline, CRPD-Sed and CRPD-Ex improved variables for cognitive function, including increased peripheral serum BDNF levels (20% and 38%), psychomotor speed and cognitive flexibility (-14%, -14%), and self-perceived cognitive symptoms and functioning (+8%, +16%), respectively. BDNF inversely correlated with %body fat (r = -0.35, P < 0.05), fasting glucose (r = -0.64, P < 0.05), triglycerides (r = -0.55, P < 0.05), and insulin sensitivity (r = -0.25, P < 0.05). Conclusion This study shows the short-term beneficial effects of carbohydrate-restricted diet on serum BDNF and executive function in those individuals characterized with MetS. We have shown that the addition of exercise can further improve neuroprotection and cognitive function beyond the results of diet alone.