Association of physiological variables with subconcussive head impacts in high school American football

ObjectiveThe purpose of this investigation was to examine the relationships between subconcussive head impact frequency and magnitude and measures of physical exertion and muscle damage.BackgroundSubconcussive head impacts, or impacts that do not present with concussion symptoms, are gaining traction as a major public health concern. However, there is a gap in knowledge about the contribution of physiological variables, such as muscle damage and physical exertion, to neurological measures used to assess subconcussive impact-dependent changes. The unknown contribution of physical exertion and strenuous exercise is often listed as a limitation in field studies of subconcussive head impacts.Design/MethodsFifteen high school football players wore mouthguards installed with triaxial accelerometers and gyroscopes in order to quantify the linear and rotational accelerations of every head impact sustained throughout one season (practices and games). Additionally, serum samples were collected at twelve time points (pre-season, pre- and post-competition for five in-season games, and post-season) and assayed for CK-MM, the skeletal muscle-specific isoenzyme of creatine kinase. Subjects wore heart rate monitors during the five games, and heart rate data were used to estimate physical exertion in terms of excess post-exercise oxygen consumption (EPOC).ResultsMixed-effect regression modeling (MRM) showed significant and positive associations between CK-MM and subconcussive head impact kinematic variables, in addition to a significant and positive association between CK-MM and EPOC. The models were adjusted for cumulative head impact exposures up to each game and the pre-season serum CK-MM levels, when applicable.ConclusionsWhen investigating subconcussive head impacts, the effects of muscle damage should be considered when using correlated outcome measures, such as inflammatory biomarkers and vestibular assessments.

Download Full-text

Association of physiological variables with football subconcussive head impacts: Why measure?

10.1101/493700 ◽

2018 ◽

Author(s):

Megan E. Huibregtse ◽

Steven W. Zonner ◽

Keisuke Ejima ◽

Zachary W. Bevilacqua ◽

Sharlene Newman ◽

...

Keyword(s):

High School ◽

Skeletal Muscle ◽

Heart Rate ◽

Muscle Damage ◽

Physical Exertion ◽

Head Impact ◽

American Football ◽

Physiological Factors ◽

Head Impacts ◽

Skeletal Muscle Damage

AbstractSubconcussive head impacts, defined as impacts to the cranium that do not result in clinical symptoms of concussion, are gaining traction as a major public health concern. Researchers begin to suggest subconcussive impact-dependent changes in various neurological measures. However, a contribution of physiological factors such as physical exertion and muscle damage has never been accounted. We conducted a prospective longitudinal study during a high school American football season to examine the association between physiological factors and subconcussive head impact kinematics. Fifteen high-school American football players volunteered in the study. A sensor-installed mouthguard recorded the number of head impacts, peak linear (PLA: g) and peak rotational (PRA: rad/s2) head accelerations from every practice and game. Serum samples were collected at 12 time points (pre-season baseline, five in-season pre-post games, and post-season) and assessed for the creatine kinase skeletal muscle-specific isoenzyme (CK-MM), as a surrogate for skeletal muscle damage. Physical exertion was estimated in the form of excess post-exercise oxygen consumption (EPOC) from heart rate data captured during five games via a wireless heart rate monitor. A total of 9,700 hits, 214,492 g, and 19,885,037 rad/s2 were recorded from 15 players across the study period. Mixed-effect regression models indicated that head impact kinematics (frequency, PLA, and PRA) were significantly and positively associated with CK-MM increase, but not with EPOC. There was a significant and positive association between CK-MM and EPOC. These data suggest that skeletal muscle damage effects should be considered when using outcome measures that may have an interaction with muscle damage, including inflammatory biomarkers and vestibular/balance tests.

Download Full-text

Association between Muscle Damage and Head Impacts in High School American Football

International Journal of Sports Medicine ◽

10.1055/a-1021-1735 ◽

2019 ◽

Vol 41 (01) ◽

pp. 36-43 ◽

Cited By ~ 1

Author(s):

Megan E. Huibregtse ◽

Steven W. Zonner ◽

Keisuke Ejima ◽

Zachary W. Bevilacqua ◽

Sharlene D. Newman ◽

...

Keyword(s):

High School ◽

Skeletal Muscle ◽

Muscle Damage ◽

Physical Exertion ◽

American Football ◽

Health Concern ◽

Physiological Factors ◽

Prospective Longitudinal Study ◽

Head Impacts ◽

Prospective Longitudinal

AbstractSubconcussive head impacts (SHI), defined as impacts to the cranium that do not result in concussion symptoms, are gaining traction as a major public health concern. The contribution of physiological factors such as physical exertion and muscle damage to SHI-dependent changes in neurological measures remains unknown. A prospective longitudinal study examined the association between physiological factors and SHI kinematics in 15 high school American football players over one season. Players wore a sensor-installed mouthguard for all practices and games, recording frequency and magnitude of all head impacts. Serum samples were collected at 12 time points (pre-season, pre- and post-game for five in-season games, and post-season) and were assessed for an isoenzyme of creatine kinase (CK-MM) primarily found in skeletal muscle. Physical exertion was estimated in the form of excess post-exercise oxygen consumption (EPOC) from heart rate data captured during the five games. Mixed-effect regression models indicated that head impact kinematics were significantly and positively associated with change in CK-MM but not EPOC. There was a significant and positive association between CK-MM and EPOC. These data suggest that when examining SHI, effects of skeletal muscle damage should be considered when using outcome measures that may have an interaction with muscle damage.

Download Full-text

Behavioral Tackling Interventions Decrease Head Impact Frequency in American Football Players: A Critically Appraised Topic

International Journal of Athletic Therapy & Training ◽

10.1123/ijatt.2020-0019 ◽

2020 ◽

pp. 1-7

Author(s):

Ashley E. Evans ◽

Madeline Curtis ◽

Marguerite (Meg) Montjoy ◽

Erica Beidler

Keyword(s):

High School ◽

Injury Prevention ◽

Head Impact ◽

American Football ◽

Football Players ◽

Clinical Question ◽

Impact Frequency ◽

Bottom Line ◽

Head Impacts ◽

Different Types

Context: The rate of sport-related concussion diagnosis has significantly increased in recent years, which has created a need for injury prevention initiatives. There have been efforts put forth by researchers and American football organizations to teach athletes how to tackle properly in order to decrease the number of subconcussive head impacts and concussions. Clinical Question: Does the implementation of a behavioral tackling intervention decrease the head impact frequency in American football players? Clinical Bottom Line: There is moderate SORT Level B evidence to support the use of behavioral tackling interventions as a means for reducing head impact frequency in football athletes. All four included studies found a significant reduction in head impacts following a behavioral tackling intervention with study findings ranging from a 26–33% reduction in impact frequency. These findings were consistent in youth, high school, and college football players and for different types of behavioral tackling interventions. Therefore, these results indicate that behavioral tackling interventions have the potential to reduce the number of head impacts sustained by American football players, which may ultimately lead to a reduction in concussion occurrence as well.

Download Full-text

Association Between Antemortem FLAIR White Matter Hyperintensities and Neuropathology in Brain Donors Exposed to Repetitive Head Impacts

Neurology ◽

10.1212/wnl.0000000000013012 ◽

2021 ◽

pp. 10.1212/WNL.0000000000013012

Author(s):

Madeline Uretsky ◽

Sylvain Bouix ◽

Ronald J. Killiany ◽

Yorghos Tripodis ◽

Brett Martin ◽

...

Keyword(s):

White Matter ◽

White Matter Hyperintensities ◽

Microvascular Disease ◽

Head Impact ◽

American Football ◽

Football Players ◽

Head Impacts ◽

Repetitive Head Impacts ◽

Pathological Correlation ◽

Daily Function

Background and Objectives:Late neuropathologies of repetitive head impacts from contact sports can include chronic traumatic encephalopathy (CTE) and white matter degeneration. White matter hyperintensities (WMH) on fluid attenuated inversion recovery (FLAIR) MRI scans are often viewed as microvascular disease from vascular risk, but might have unique underlying pathologies and risk factors in the setting of repetitive head impacts. We investigated the neuropathological correlates of antemortem WMH in brain donors exposed to repetitive head impacts. The association between WMH, and repetitive head impact exposure and informant-reported cognitive and daily function were tested.Methods:This imaging-pathological correlation study included symptomatic deceased men exposed to repetitive head impacts. Donors had antemortem FLAIR scans from medical records and were without evidence of CNS neoplasm, large vessel infarcts, hemorrhage, and/or encephalomalacia. WMH were quantified using log-transformed values for total lesion volume (TLV), calculated using the lesion prediction algorithm from the Lesion Segmentation Toolbox. Neuropathological assessments included semi-quantitative ratings of white matter rarefaction, cerebrovascular disease, p-tau severity (CTE stage, dorsolateral frontal cortex), and Aβ. Among football players, years of play was a proxy for repetitive head impact exposure. Retrospective informant-reported cognitive and daily function were assessed using the Cognitive Difficulties Scale (CDS) and Functional Activities Questionnaire (FAQ). Regression models controlled for demographics, diabetes, hypertension, and MRI resolution. Statistical significance was defined as p<0.05.Results:The sample included 75 donors: 67 football players and 8 non-football contact sport athletes and/or military veterans. Dementia was the most common MRI indication (64%). Fifty-three (70.7%) had CTE at autopsy. Log-TLV was associated with white matter rarefaction (OR=2.32, 95% CI=1.03,5.24, p=0.04), arteriolosclerosis (OR=2.38, 95% CI=1.02,5.52, p=0.04), CTE stage (OR=2.58, 95% CI=1.17,5.71, p=0.02), and dorsolateral frontal p-tau severity (OR=3.03, 95% CI=1.32,6.97, p=0.01). There was no association with Aβ. More years of football play was associated with log-TLV (b=0.04, 95% CI=0.01,0.06, p=0.01). Greater log-TLV correlated with higher FAQ (unstandardized beta=4.94, 95% CI=0.42,8.57, p=0.03) and CDS scores (unstandardized beta=15.35, 95% CI=-0.27,30.97, p=0.05).Discussion:WMH might capture long-term white matter pathologies from repetitive head impacts, including those from white matter rarefaction and p-tau, in addition to microvascular disease. Prospective imaging-pathological correlation studies are needed.Classification of Evidence:This study provides Class IV evidence of associations between FLAIR white matter hyperintensities, and neuropathological changes (white matter rarefaction, arteriolosclerosis, p-tau accumulation), years of American football play, and reported cognitive symptoms in symptomatic brain donors exposed to repetitive head impacts.

Download Full-text

Game-Related Impacts in High School Boys’ Lacrosse

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967119835587 ◽

2019 ◽

Vol 7 (4) ◽

pp. 232596711983558 ◽

Cited By ~ 2

Author(s):

Shane V. Caswell ◽

Patricia Kelshaw ◽

Andrew E. Lincoln ◽

Lisa Hepburn ◽

Reginald Dunn ◽

...

Keyword(s):

High School ◽

Rotational Velocity ◽

Linear Acceleration ◽

The United States ◽

Head Impact ◽

Level Of Evidence ◽

Cross Sectional ◽

Head Impacts ◽

Direct Head ◽

The Impact

Background: The rate of concussions in boys’ lacrosse is reported to be the third highest among high school sports in the United States, but no studies have described game-related impacts among boys’ lacrosse players. Purpose: To characterize verified game-related impacts, both overall and those directly to the head, in boys’ varsity high school lacrosse. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 77 male participants (mean age, 16.6 ± 1.2 years; mean height, 1.77 ± 0.05 m; mean weight, 73.4 ± 12.2 kg) were instrumented with sensors and were videotaped during 39 games. All verified game-related impacts ≥20 g were summarized in terms of frequency, peak linear acceleration (PLA), and peak rotational velocity (PRV). Descriptive statistics and impact rates per player-game (PG) with corresponding 95% CIs were calculated. Results: Overall, 1100 verified game-related impacts were recorded (PLA: median, 33.5 g [interquartile range (IQR), 25.7-51.2]; PRV: median, 1135.5 deg/s [IQR, 790.0-1613.8]) during 795 PGs. The rate for all verified game-related impacts was 1.38 impacts per PG (95% CI, 1.30-1.47). Of these, 680 (61.8%) impacts (PLA: median, 35.9 g [IQR, 26.7-55.5]; PRV: 1170.5 deg/s [IQR, 803.2-1672.8]) were directly to the head (impact rate, 0.86 impacts/PG [95% CI, 0.79-0.92]). Overall, midfielders (n = 514; 46.7%) sustained the most impacts, followed by attackers (n = 332; 30.2%), defenders (n = 233; 21.2%), and goalies (n = 21; 1.9%). The most common mechanisms for overall impacts and direct head impacts were contact with player (overall: n = 706 [64.2%]; head: n = 397 [58.4%]) and stick (overall: n = 303 [27.5%]; head: n = 239 [35.1%]), followed by ground (overall: n = 73 [6.6%]; head: n = 26 [3.8%]) and ball (overall: n = 15 [1.4%]; head: n = 15 [2.2%]). Direct head impacts were associated with a helmet-to-helmet collision 31.2% of the time, and they were frequently (53.7%) sustained by the players delivering the impact. Nearly half (48.8%) of players delivering contact used their helmets to initiate contact that resulted in a helmet-to-helmet impact. Players receiving a head impact from player contact were most often unprepared (75.9%) for the collision. Conclusion: The helmet is commonly used to initiate contact in boys’ high school lacrosse, often targeting defenseless opponents. Interventions to reduce head impacts should address rules and coaching messages to discourage intentional use of the helmet and encourage protection of defenseless opponents.

Download Full-text

Biomechanical head impact characteristics during sparring practice sessions in high school taekwondo athletes

Journal of Neurosurgery Pediatrics ◽

10.3171/2017.1.peds16432 ◽

2017 ◽

Vol 19 (6) ◽

pp. 662-667 ◽

Cited By ~ 3

Author(s):

David M. O'Sullivan ◽

Gabriel P. Fife

Keyword(s):

High School ◽

Rotational Velocity ◽

Linear Acceleration ◽

Head Impact ◽

Rotational Acceleration ◽

Head Impacts ◽

Head Injury Criterion ◽

Impact Location ◽

Male High School ◽

Impact Characteristics

OBJECTIVEThe purpose of this study was to monitor head impact magnitude and characteristics, such as impact location and frequency, at high school taekwondo sparring sessions.METHODSEight male high school taekwondo athletes participated in this study. The head impact characteristics were recorded by X-Patch, a wireless accelerometer and gyroscope, during 6 taekwondo sparring sessions. The outcome measures were the peak linear acceleration (g = 9.81 msec2), peak rotational acceleration, rotational velocity, and Head Injury Criterion.RESULTSA total of 689 impacts occurred over 6 sessions involving the 8 athletes. There was an average of 24 impacts per 100 minutes, and there were significant differences in the frequency of impacts among both the sessions and individual athletes. In order of frequency, the most commonly hit locations were the side (38.2%), back (35.7%), and front (23.8%) of the head.CONCLUSIONSThe data indicate that there is a relatively high number of head impacts experienced by taekwondo athletes during sparring practice. According to the rotational acceleration predicting impact severity published in previous research, 17.1% of the impacts were deemed to be a moderate and 15.5% were deemed to be severe.

Download Full-text

Similar head impact acceleration measured using instrumented ear patches in a junior rugby union team during matches in comparison with other sports

Journal of Neurosurgery Pediatrics ◽

10.3171/2015.12.peds15605 ◽

2016 ◽

Vol 18 (1) ◽

pp. 65-72 ◽

Cited By ~ 15

Author(s):

Doug A. King ◽

Patria A. Hume ◽

Conor Gissane ◽

Trevor N. Clark

Keyword(s):

Injury Risk ◽

Linear Acceleration ◽

Rugby Union ◽

Head Impact ◽

American Football ◽

Football Players ◽

Head Impacts ◽

Impact Acceleration ◽

The Impact ◽

Rugby Players

OBJECTIVE Direct impact with the head and the inertial loading of the head have been postulated as major mechanisms of head-related injuries, such as concussion. METHODS This descriptive observational study was conducted to quantify the head impact acceleration characteristics in under-9-year-old junior rugby union players in New Zealand. The impact magnitude, frequency, and location were collected with a wireless head impact sensor that was worn by 14 junior rugby players who participated in 4 matches. RESULTS A total of 721 impacts > 10g were recorded. The median (interquartile range [IQR]) number of impacts per player was 46 (IQR 37–58), resulting in 10 (IQR 4–18) impacts to the head per player per match. The median impact magnitudes recorded were 15g (IQR 12g–21g) for linear acceleration and 2296 rad/sec2 (IQR 1352–4152 rad/sec2) for rotational acceleration. CONCLUSIONS There were 121 impacts (16.8%) above the rotational injury risk limit and 1 (0.1%) impact above the linear injury risk limit. The acceleration magnitude and number of head impacts in junior rugby union players were higher than those previously reported in similar age-group sports participants. The median linear acceleration for the under-9-year-old rugby players were similar to 7- to 8-year-old American football players, but lower than 9- to 12-year-old youth American football players. The median rotational accelerations measured were higher than the median and 95th percentiles in youth, high school, and collegiate American football players.

Download Full-text

High Energy American Football Head Impacts to the Side and Rear Damaging Than to the Front

Neurology ◽

10.1212/01.wnl.0000580920.17339.01 ◽

2019 ◽

Vol 93 (14 Supplement 1) ◽

pp. S10.1-S10

Author(s):

Adam Bartsch ◽

Edward Benzel ◽

Sergey Samorezov ◽

Vincent Miele

Keyword(s):

High Energy ◽

Head Impact ◽

American Football ◽

Dose Response Relationship ◽

Positive Events ◽

Head Impacts ◽

Injury Threshold ◽

Impact Location ◽

Player Game ◽

Concussive Injury

ObjectiveThe aim of this study was to investigate head impact doses in American football. We analyzed time-synchronized video and data collected during n = 445 player-games of American football resulting in 2851video-verified impacts. Cases where a player sustained impacts and on video was demonstrably witnessed to meet the NFL’s “No-go” criteria were analyzed in-depth.BackgroundIn 2011, after reviewing scalar on-field kinematics data leading concussion clinicians concluded “Recent studies suggest that a concussive injury threshold is elusive, and may, in fact, be irrelevant when predicting the clinical outcome”.1 It is likely that higher fidelity estimates of spatial and temporal impact parameters will clarify the currently unclear impact dose-response relationship.Design/MethodsA total of 2851 video-verified head impacts were identified from 445 player-games. Each event was time-synchronized to video. Any events collected when the athlete was not being impacted in the head were discarded. The remaining true positive events were scrutinized based on published methods to confirm a head impact occurred in the video and the computed motion was physically realistic and matched the video.ResultsWe found a median of 5 video-verified head impacts per player-game, which is far fewer than published studies without video verification.11 For the four players with “No-go” impacts, all were to the side/rear. Coronal plane impact sensitivity has been a hypothesized clinical injury mechanism12 and our results support that hypothesis.ConclusionsWe did not see high PLA/PAA impacts without obvious player “No-go” observations. This finding disagrees with other studies that have reported high PLA/PAA impacts without any demonstrable “No-go” observations13. High energy impacts to the side and rear of the head are more damaging than similar magnitude impacts to the forehead. Armed with this knowledge, clinicians should have more fidelity in their understanding of real-time impact location and severity, and how it relates to athlete concussion risk.

Download Full-text

Subconcussive head impact exposure differences between drill intensities in U.S. high school football

10.1101/2020.03.29.20047167 ◽

2020 ◽

Author(s):

Kyle Kercher ◽

Jesse A. Steinfeldt ◽

Jonathan T. Macy ◽

Keisuke Ejima ◽

Keisuke Kawata

Keyword(s):

High School ◽

Linear Acceleration ◽

Head Impact ◽

Football Players ◽

Impact Frequency ◽

High School Football ◽

Head Impacts ◽

Air Bags ◽

Frequency Peak ◽

Impact Data

ABSTRACTPurposeUSA Football established five levels of contact (LOC) to guide the intensity of high school football practices. However, it remains unclear whether head impact exposure differs by LOC. The purpose of this study was to examine head impact frequency and magnitude by LOC in the overall sample and three position groups.MethodsThis longitudinal observational study included 24 high school football players during all practices and games in the 2019 season. Players wore a sensor-installed mouthguard that monitored head impact frequency, peak linear acceleration (PLA), and rotational head acceleration (PRA). Practice/game drills were filmed and categorized into 5 LOCs (air, bags, control, thud, live), and head impact data were assigned into 5 LOCs. Player position was categorized into linemen, hybrid, and skill.ResultsA total of 6016 head impacts were recorded during 5 LOCs throughout the season. In the overall sample, total number of impacts, sum of PLA, and PRA per player increased in an incremental manner (air<bags<control<thud<live), with the most head impacts in live (113.7±17.8 hits/player) and the least head impacts in air (7.7±1.9 hits/player). The linemen and hybrid groups had consistently higher impact exposure than the skill group. Average head impact magnitudes by position group were higher during live drills (PLA (41.0-45.9g) and PRA (3.3-4.6 krad/s2) per head impact), whereas other LOCs had lower magnitudes (PLA (18.2-23.2g) and PRA (1.6-2.3krad/s2) per impact).ConclusionOur data suggest that LOC may influence cumulative head impact exposure in high school football, with players incurring frequent head impacts during live, thud, and control. The data indicate the importance of considering LOCs to refine practice guidelines and policies to minimize head impact burden in high school football athletes.

Download Full-text

Head Impact Exposure and Mechanisms in Female High School Lacrosse via an Instrumented Mouthguard

Neurology ◽

10.1212/01.wnl.0000801856.45976.d2 ◽

2021 ◽

Vol 98 (1 Supplement 1) ◽

pp. S13.2-S14

Author(s):

Colin M. Huber ◽

Declan A. Patton ◽

Susan Margulies ◽

Christina Master ◽

Kristy Arbogast

Keyword(s):

High School ◽

Angular Acceleration ◽

Head Impact ◽

Sensor Data ◽

Current Debate ◽

Protective Equipment ◽

Impact Mechanism ◽

Head Impacts ◽

Impact Biomechanics ◽

Female High School

ObjectiveTo quantify the head impact biomechanics, by impact mechanism, of female high school lacrosse players during games using an instrumented mouthguard.BackgroundThere is growing concern for the neurologic effects of repetitive head impacts in sports, which have been linked with several short-term neurophysiologic deficits. Girls' lacrosse represents a popular but understudied sport with regard to head impact exposure and current debate exists as to the need for enhanced protective equipment.Design/MethodsA female high school varsity lacrosse team wore the Stanford Instrumented Mouthguard during competitive games for the 2019 season. Video footage was reviewed to confirm head impact events and remove false-positive recordings. For each impact event, the mechanism was coded as stick contact, player contact, fall, or ball contact. Head impact rates were calculated per athlete exposure (AE, defined as a single player participating in a single game).ResultsSensor data were recorded for 15 female varsity lacrosse players for 14 games and 97 AEs. During games, 31 sensor-recorded head impacts were video-confirmed resulting in a pooled average head impact rate of 0.32 impacts/AE. The video-confirmed impacts were distributed between stick contact (17, 54.8%), player contact (12, 38.7%), and falls (2, 6.5%). There were no ball impacts. Overall peak kinematics were 34.0 ± 26.6 g, 12.0 ± 9.1 rad/s, and 3,666.5 ± 2,987.6 rad/s2. Stick contacts had the highest peak linear acceleration (42.7 ± 32.2 g), angular velocity (14.5 ± 11.1 rad/s), and angular acceleration (4,242.4 ± 3,634.9 rad/s2).ConclusionsStick impacts were the most common impact mechanism and resulted in the highest peak linear and angular kinematics, which may help explain why they are the most common cause of head injury in female lacrosse. By quantifying the head impact exposure, kinematics and mechanisms in female high school lacrosse, targeted injury preventions can be developed, such as rule changes and protective equipment.

Download Full-text