human
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Abstract The biology of post-concussive symptoms is unclear . Symptoms are often increased during activities , and have been linked to decreased cerebrovascular reactivity and perfusion . The aim of this study was to examine cerebral blood flow ( CBF ) in children with different clinical recovery patterns following mild traumatic brain injury ( mTBI ) . This was a prospect i ve controlled cohort study of children with mTBI ( ages 8 to 18 years ) who were symptomatic with post-concussive symptoms at one month post-injury ( symptomatic , n = 27 ) and children who had recovered quickly ( asymptomatic , n = 24 ) .  Pseudo continuous arterial spin labeling magnetic resonance imaging ( MRI ) was used to quantify CBF . The mTBI groups were imaged at 40 days post-injury . Global and regional CBF were compared with healthy controls of similar age and sex but without a history of mTBI ( n = 21 ) . Seventy-two participants ( mean age : 14.1 years ) underwent neuroimaging . Significant differences in CBF were found : global CBF was higher in the symptomatic group and lower in the asymptomatic group compared with controls , ( F(2,69 ) 9.734 ; p < 0.001 ) . Post-injury symptom score could be predicted by pre-injury symptoms and CBF in presence of mTBI ( adjusted R2 = 0.424 ; p < 0.001 ) . Altered patterns of cerebral perfusion are seen following mTBI and are associated with the recovery trajectory . Symptomatic children have higher CBF . Children who “ recovered ” quickly , have decreased CBF suggesting that clinical recovery precedes the cerebral recovery . Further longitudinal studies are required to determine if these perfusion patterns continue to change over time Objective : Some patients with postconcussion syndrome ( PCS ) have reduced exercise capacity that may reflect altered central cardiorespiratory control . The purpose of this study was to evaluate control of cerebral blood flow ( CBF ) during exercise in females with PCS . Setting : University Concussion Clinic . Participants : Nine female Division 1 collegiate team athletes with PCS ( 23 ± 6 years ) and a reference group of 13 healthy female recreational aerobic athletes ( 21 ± 3 years ) . Design : A prospect i ve experimental study . All PCS athletes were compared with the reference group at the beginning of the study . Six of the PCS athletes were subsequently measured before and after a subsymptom threshold aerobic exercise treatment program . Main Measures : Exercise treadmill test  during which blood pressure ( BP ) , minute ventilation ( E ) , end-tidal CO2 ( PETCO2 ) , and CBF velocity ( CBFV , by transcranial Doppler ) were measured . Results : Participants with PCS had significantly lower E ( by 18 % ) and greater PETCO2 ( 5 % ) and CBFV ( 14 % ) versus the reference group at similar workloads in association with appearance of symptoms and premature exercise cessation . Subthreshold exercise normalized E , PETCO2 , CBFV and exercise tolerance . Before treatment , PCS had low CO2 sensitivity that blunted their exercise ventilation . CO2 sensitivity and ventilation improved after exercise treatment . Conclusion : Some PCS patients have exercise intolerance due to abnormal CBF regulation that may be the result of concussion-induced altered sensitivity to CO2 . Return of normal CBF control and exercise tolerance may be physiological markers of recovery from concussion Aim To investigate incidence of concussion , clinical outcomes and subsequent injury risk following concussion . Methods In a two-season ( 2012/2013 , 2013/2014 ) prospect i ve cohort study , incidence of diagnosed match concussions ( injuries/1000 h ) , median time interval to subsequent injury of any type ( survival time ) and time spent at each stage of the graduated return to play pathway were determined in 810 professional Rugby Union players ( 1176 player seasons ) . Results Match concussion incidence was 8.9/1000 h with over 50 % occurring in the tackle . Subsequent incidence of any injury for players who returned to play in the same season following a diagnosed concussion ( 122/1000 h , 95 % CI 106 to 141 ) was 60 % higher ( IRR 1.6 , 95 % CI 1.4 to 1.8 ) than for those who did not sustain a concussion ( 76/1000 h , 95 % CI 72 to 80 ) . Median time to next injury following return to play was shorter following concussion ( 53 days , 95 % CI 41 to 64 ) than following non-concussive injuries ( 114 days , 95 % CI 85 to 143 ) . 38 % of players reported recurrence of symptoms or failed to match their baseline neurocognitive test during the graduated return to play protocol . Summary and conclusions Players who returned to play in the same season after a diagnosed concussion had a 60 % greater risk of time-loss injury than players without concussion . A substantial proportion of players reported recurrence of symptoms or failed to match baseline neurocognitive test scores during graduated return to play . These data pave the way for trials of more conservative and comprehensive graduated return to play protocol s , with a greater focus on active rehabilitation The arterial pulse wave ( APW ) has a distinct morphology whose contours reflect dynamics in cardiac function and peripheral vascular tone as a result of sympathetic nervous system ( SNS ) control . With a transition from rest to increased metabolic dem and , the expected augmentation of SNS outflow will not only affect arterial blood pressure and heart rate but it will also induce changes to the contours of the APW . Following a sports concussion , a transient state cardiovascular autonomic dysfunction is present . How this state affects the APW has yet to be described . A prospect i ve , parallel-group study on cardiovascular autonomic control ( i.e. , digital electrocardiogram and continuous beat-to-beat blood pressure ) was performed in the seated upright position in 10 athletes with concussion and 7 non-injured control athletes .  Changes in APW were compared at rest and during the first 60 s ( F60 ) of an isometric h and grip test ( IHGT ) in concussed athletes and non-injured controls within 48 h and 1 week of injury . The concussion group was further separated by the length of time until they were permitted to return to play ( RTP > 1week ; RTP ≤ 1week ) . SysSlope , an indirect measurement of stroke volume , was significantly lower in the concussion group at rest and during F60 at 48 h and 1week ; a paradoxical decline in SysSlope occurred at each visit during the transition from rest to IHGT F60 . The RTP > 1week group had lower SysSlope ( 405 ± 200 ; 420 ± 88 ; 454 ± 236 mmHg/s , respectively ) at rest 48 h compared to the RTP ≤ 1week and controls . Similarly at 48 h rest , several measurements of arterial stiffness were abnormal in RTP > 1week compared to RTP ≤ 1week and controls : peak-to-notch latency ( 0.12 ± 0.04 ; 0.16 ± 0.02 ; 0.17 ± 0.05 , respectively ) , notch relative amplitude ( 0.70 ± 0.03 ; 0.71 ± 0.04 ; 0.66 ± 0.14 , respectively ) , and stiffness index ( 6.4 ± 0.2 ; 5.7 ± 0.4 ; 5.8 ± 0.5 , respectively ) . Use of APW revealed that concussed athletes have a transient increase in peripheral artery stiffness , which may be a compensatory adaptation to a paradoxical decline of stroke volume during the transition from rest to a state of increased metabolic dem and within 48 h of concussion . This dysfunction of the SNS appeared to be more pronounced among concussed athletes who were removed from participation for > 1 week compared to those who resumed play within 7 days Objective Increased awareness around neurocognitive deficits after mild traumatic brain injury ( mTBI ) has progressed the search for objective , diagnostic , and monitoring tools , yet imaging biomarkers for mTBI and recovery are not established in clinical use . It has been suggested that mTBI impairs cerebrovascular reactivity ( CVR ) to CO2 , which could be related to post-concussive syndrome ( PCS ) . We investigate CVR evolution after mTBI using blood-oxygen-level dependent ( BOLD ) magnetic resonance imaging ( MRI ) and possible correlation with PCS . Methods A prospect i ve cohort of 25 mTBI patients and 18 matched controls underwent BOLD MRI CVR measurements . A subset of 19 mTBI patients underwent follow-up testing . Visits took place at a mean of 63 and 180 days after injury . Symptoms were assessed with the  Sport Concussion Assessment Tool 2 ( SCAT2 ) . Symptoms , CVR and brain volume [ gray matter ( GM ) , white matter ( WM ) , and whole brain ( WB ) ] , age , and sex , were examined between groups and longitudinally within traumatic brain injury ( TBI ) patients . Results Traumatic brain injury participants were 72 % males , mean age being 42.7 years . Control participants were 61 % with mean age of 38.7 years .  SCAT2 scores tended to improve among those mTBI patients with follow-up visits ( p = 0.07 ) ; however , they did not tend to recover to scores of the healthy controls . Brain volumes were not statistically different between groups at the first visit ( WM p = 0.71 ; GM p = 0.36 ) . In mTBI patients , there was a reduction in GM volume between visits 1 and 2 ( p = 0.0046 ) . Although mean CVR indexes were similar ( WM p = 0.27 ; GM p = 0.36 ; and WB p = 0.35 ) , the correlation between SCAT2 and CVR was negative in controls ( WM-r = −0.59 ; p = 0.010 ; GM-r = −0.56 ; p = 0.016 ; brain-r = −0.58 ; p = 0.012 ) and weaker and positive in mTBI ( brain-r = 0.4 ; p = 0.046 ; GM-r = 0.4 ; p = 0.048 ) . SCAT2 correlated with GM volume ( r = 0.5215 , p = 0.0075 ) in mTBI but not in controls ( r = 0.2945 , p = 0.2355 ) . Conclusion There is a correlation between lower GM CVR indexes and lower performance on SCAT2 in patients with mTBI , which seems to be associated with more symptoms . This correlation seems to persist well beyond 120 days . mTBI may lead to a decrease in GM volume in these patients Background The on-field diagnosis of sports-related concussion ( SRC ) is complicated by the lack of an accurate and objective marker of brain injury . Purpose To compare subject-specific changes in the astroglial protein , S100B , before and after SRC among collegiate and semi-professional contact sport athletes , and compare these changes to differences in S100B before and after non-contact exertion . Study Design Longitudinal cohort study . Methods From 2009–2011 , we performed a prospect i ve study of athletes from Munich , Germany , and Rochester , New York , USA .  Serum S100B was measured in all SRC athletes at pre-season baseline , within 3 hours of injury , and at days 2 , 3 and 7 post-SRC . Among a subset of athletes , S100B was measured after non-contact exertion but before injury . All sample s were collected identically and analyzed using an automated electrochemiluminescent assay to quantify serum S100B levels . Results Forty-six athletes ( 30 Munich , 16 Rochester ) underwent baseline testing . Thirty underwent additional post-exertion S100B testing . Twenty-two athletes ( 16 Rochester , 6 Munich ) sustained a SRC , and 17 had S100B testing within 3 hours post-injury . The mean 3-hour post-SRC S100B was significantly higher than pre-season baseline ( 0.099±0.008 µg/L vs. 0.058±0.006 µg/L , p = 0.0002 ) . Mean post-exertion S100B was not significantly different than the preseason baseline . S100B levels at post-injury days 2 , 3 and 7 were significantly lower than the 3-hour level , and not different than baseline . Both the absolute change and proportional increase in S100B 3-hour post-injury were accurate discriminators of SRC from non-contact exertion without SRC ( AUC 0.772 and 0.904 , respectively ) . A 3-hour post-concussion S100B > 0.122 µg/L and a proportional S100B increase of > 45.9 % over baseline were both 96.7 % specific for SRC . Conclusions Relative and absolute increases in serum S100B can accurately distinguish SRC from sports-related exertion , and may be a useful adjunct to the diagnosis of SRC Our aim was to quantify with functional magnetic resonance imaging ( fMRI ) changes in brain activity in concussed athletes and 
    Output:
    
agent
Due to differences in modalities , time course , study design and outcomes , it is not possible to define a single ‘ physiological time window ’ for SRC recovery .
Multiple studies suggest physiological dysfunction may outlast current clinical measures of recovery , supporting a buffer zone of gradually increasing activity before full contact risk .
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Abstract The biology of post-concussive symptoms is unclear . Symptoms are often increased during activities , and have been linked to decreased cerebrovascular reactivity and perfusion . The aim of this study was to examine cerebral blood flow ( CBF ) in children with different clinical recovery patterns following mild traumatic brain injury ( mTBI ) . This was a prospect i ve controlled cohort study of children with mTBI ( ages 8 to 18 years ) who were symptomatic with post-concussive symptoms at one month post-injury ( symptomatic , n = 27 ) and children who had recovered quickly ( asymptomatic , n = 24 ) .  Pseudo continuous arterial spin labeling magnetic resonance imaging ( MRI ) was used to quantify CBF . The mTBI groups were imaged at 40 days post-injury . Global and regional CBF were compared with healthy controls of similar age and sex but without a history of mTBI ( n = 21 ) . Seventy-two participants ( mean age : 14.1 years ) underwent neuroimaging . Significant differences in CBF were found : global CBF was higher in the symptomatic group and lower in the asymptomatic group compared with controls , ( F(2,69 ) 9.734 ; p < 0.001 ) . Post-injury symptom score could be predicted by pre-injury symptoms and CBF in presence of mTBI ( adjusted R2 = 0.424 ; p < 0.001 ) . Altered patterns of cerebral perfusion are seen following mTBI and are associated with the recovery trajectory . Symptomatic children have higher CBF . Children who “ recovered ” quickly , have decreased CBF suggesting that clinical recovery precedes the cerebral recovery . Further longitudinal studies are required to determine if these perfusion patterns continue to change over time Objective : Some patients with postconcussion syndrome ( PCS ) have reduced exercise capacity that may reflect altered central cardiorespiratory control . The purpose of this study was to evaluate control of cerebral blood flow ( CBF ) during exercise in females with PCS . Setting : University Concussion Clinic . Participants : Nine female Division 1 collegiate team athletes with PCS ( 23 ± 6 years ) and a reference group of 13 healthy female recreational aerobic athletes ( 21 ± 3 years ) . Design : A prospect i ve experimental study . All PCS athletes were compared with the reference group at the beginning of the study . Six of the PCS athletes were subsequently measured before and after a subsymptom threshold aerobic exercise treatment program . Main Measures : Exercise treadmill test  during which blood pressure ( BP ) , minute ventilation ( E ) , end-tidal CO2 ( PETCO2 ) , and CBF velocity ( CBFV , by transcranial Doppler ) were measured . Results : Participants with PCS had significantly lower E ( by 18 % ) and greater PETCO2 ( 5 % ) and CBFV ( 14 % ) versus the reference group at similar workloads in association with appearance of symptoms and premature exercise cessation . Subthreshold exercise normalized E , PETCO2 , CBFV and exercise tolerance . Before treatment , PCS had low CO2 sensitivity that blunted their exercise ventilation . CO2 sensitivity and ventilation improved after exercise treatment . Conclusion : Some PCS patients have exercise intolerance due to abnormal CBF regulation that may be the result of concussion-induced altered sensitivity to CO2 . Return of normal CBF control and exercise tolerance may be physiological markers of recovery from concussion Aim To investigate incidence of concussion , clinical outcomes and subsequent injury risk following concussion . Methods In a two-season ( 2012/2013 , 2013/2014 ) prospect i ve cohort study , incidence of diagnosed match concussions ( injuries/1000 h ) , median time interval to subsequent injury of any type ( survival time ) and time spent at each stage of the graduated return to play pathway were determined in 810 professional Rugby Union players ( 1176 player seasons ) . Results Match concussion incidence was 8.9/1000 h with over 50 % occurring in the tackle . Subsequent incidence of any injury for players who returned to play in the same season following a diagnosed concussion ( 122/1000 h , 95 % CI 106 to 141 ) was 60 % higher ( IRR 1.6 , 95 % CI 1.4 to 1.8 ) than for those who did not sustain a concussion ( 76/1000 h , 95 % CI 72 to 80 ) . Median time to next injury following return to play was shorter following concussion ( 53 days , 95 % CI 41 to 64 ) than following non-concussive injuries ( 114 days , 95 % CI 85 to 143 ) . 38 % of players reported recurrence of symptoms or failed to match their baseline neurocognitive test during the graduated return to play protocol . Summary and conclusions Players who returned to play in the same season after a diagnosed concussion had a 60 % greater risk of time-loss injury than players without concussion . A substantial proportion of players reported recurrence of symptoms or failed to match baseline neurocognitive test scores during graduated return to play . These data pave the way for trials of more conservative and comprehensive graduated return to play protocol s , with a greater focus on active rehabilitation The arterial pulse wave ( APW ) has a distinct morphology whose contours reflect dynamics in cardiac function and peripheral vascular tone as a result of sympathetic nervous system ( SNS ) control . With a transition from rest to increased metabolic dem and , the expected augmentation of SNS outflow will not only affect arterial blood pressure and heart rate but it will also induce changes to the contours of the APW . Following a sports concussion , a transient state cardiovascular autonomic dysfunction is present . How this state affects the APW has yet to be described . A prospect i ve , parallel-group study on cardiovascular autonomic control ( i.e. , digital electrocardiogram and continuous beat-to-beat blood pressure ) was performed in the seated upright position in 10 athletes with concussion and 7 non-injured control athletes .  Changes in APW were compared at rest and during the first 60 s ( F60 ) of an isometric h and grip test ( IHGT ) in concussed athletes and non-injured controls within 48 h and 1 week of injury . The concussion group was further separated by the length of time until they were permitted to return to play ( RTP > 1week ; RTP ≤ 1week ) . SysSlope , an indirect measurement of stroke volume , was significantly lower in the concussion group at rest and during F60 at 48 h and 1week ; a paradoxical decline in SysSlope occurred at each visit during the transition from rest to IHGT F60 . The RTP > 1week group had lower SysSlope ( 405 ± 200 ; 420 ± 88 ; 454 ± 236 mmHg/s , respectively ) at rest 48 h compared to the RTP ≤ 1week and controls . Similarly at 48 h rest , several measurements of arterial stiffness were abnormal in RTP > 1week compared to RTP ≤ 1week and controls : peak-to-notch latency ( 0.12 ± 0.04 ; 0.16 ± 0.02 ; 0.17 ± 0.05 , respectively ) , notch relative amplitude ( 0.70 ± 0.03 ; 0.71 ± 0.04 ; 0.66 ± 0.14 , respectively ) , and stiffness index ( 6.4 ± 0.2 ; 5.7 ± 0.4 ; 5.8 ± 0.5 , respectively ) . Use of APW revealed that concussed athletes have a transient increase in peripheral artery stiffness , which may be a compensatory adaptation to a paradoxical decline of stroke volume during the transition from rest to a state of increased metabolic dem and within 48 h of concussion . This dysfunction of the SNS appeared to be more pronounced among concussed athletes who were removed from participation for > 1 week compared to those who resumed play within 7 days Objective Increased awareness around neurocognitive deficits after mild traumatic brain injury ( mTBI ) has progressed the search for objective , diagnostic , and monitoring tools , yet imaging biomarkers for mTBI and recovery are not established in clinical use . It has been suggested that mTBI impairs cerebrovascular reactivity ( CVR ) to CO2 , which could be related to post-concussive syndrome ( PCS ) . We investigate CVR evolution after mTBI using blood-oxygen-level dependent ( BOLD ) magnetic resonance imaging ( MRI ) and possible correlation with PCS . Methods A prospect i ve cohort of 25 mTBI patients and 18 matched controls underwent BOLD MRI CVR measurements . A subset of 19 mTBI patients underwent follow-up testing . Visits took place at a mean of 63 and 180 days after injury . Symptoms were assessed with the  Sport Concussion Assessment Tool 2 ( SCAT2 ) . Symptoms , CVR and brain volume [ gray matter ( GM ) , white matter ( WM ) , and whole brain ( WB ) ] , age , and sex , were examined between groups and longitudinally within traumatic brain injury ( TBI ) patients . Results Traumatic brain injury participants were 72 % males , mean age being 42.7 years . Control participants were 61 % with mean age of 38.7 years .  SCAT2 scores tended to improve among those mTBI patients with follow-up visits ( p = 0.07 ) ; however , they did not tend to recover to scores of the healthy controls . Brain volumes were not statistically different between groups at the first visit ( WM p = 0.71 ; GM p = 0.36 ) . In mTBI patients , there was a reduction in GM volume between visits 1 and 2 ( p = 0.0046 ) . Although mean CVR indexes were similar ( WM p = 0.27 ; GM p = 0.36 ; and WB p = 0.35 ) , the correlation between SCAT2 and CVR was negative in controls ( WM-r = −0.59 ; p = 0.010 ; GM-r = −0.56 ; p = 0.016 ; brain-r = −0.58 ; p = 0.012 ) and weaker and positive in mTBI ( brain-r = 0.4 ; p = 0.046 ; GM-r = 0.4 ; p = 0.048 ) . SCAT2 correlated with GM volume ( r = 0.5215 , p = 0.0075 ) in mTBI but not in controls ( r = 0.2945 , p = 0.2355 ) . Conclusion There is a correlation between lower GM CVR indexes and lower performance on SCAT2 in patients with mTBI , which seems to be associated with more symptoms . This correlation seems to persist well beyond 120 days . mTBI may lead to a decrease in GM volume in these patients Background The on-field diagnosis of sports-related concussion ( SRC ) is complicated by the lack of an accurate and objective marker of brain injury . Purpose To compare subject-specific changes in the astroglial protein , S100B , before and after SRC among collegiate and semi-professional contact sport athletes , and compare these changes to differences in S100B before and after non-contact exertion . Study Design Longitudinal cohort study . Methods From 2009–2011 , we performed a prospect i ve study of athletes from Munich , Germany , and Rochester , New York , USA .  Serum S100B was measured in all SRC athletes at pre-season baseline , within 3 hours of injury , and at days 2 , 3 and 7 post-SRC . Among a subset of athletes , S100B was measured after non-contact exertion but before injury . All sample s were collected identically and analyzed using an automated electrochemiluminescent assay to quantify serum S100B levels . Results Forty-six athletes ( 30 Munich , 16 Rochester ) underwent baseline testing . Thirty underwent additional post-exertion S100B testing . Twenty-two athletes ( 16 Rochester , 6 Munich ) sustained a SRC , and 17 had S100B testing within 3 hours post-injury . The mean 3-hour post-SRC S100B was significantly higher than pre-season baseline ( 0.099±0.008 µg/L vs. 0.058±0.006 µg/L , p = 0.0002 ) . Mean post-exertion S100B was not significantly different than the preseason baseline . S100B levels at post-injury days 2 , 3 and 7 were significantly lower than the 3-hour level , and not different than baseline . Both the absolute change and proportional increase in S100B 3-hour post-injury were accurate discriminators of SRC from non-contact exertion without SRC ( AUC 0.772 and 0.904 , respectively ) . A 3-hour post-concussion S100B > 0.122 µg/L and a proportional S100B increase of > 45.9 % over baseline were both 96.7 % specific for SRC . Conclusions Relative and absolute increases in serum S100B can accurately distinguish SRC from sports-related exertion , and may be a useful adjunct to the diagnosis of SRC Our aim was to quantify with functional magnetic resonance imaging ( fMRI ) changes in brain activity in concussed athletes and 
    Output:
    