Patterns of head impact exposure in men's and women's collegiate club water polo

Incidence of Concussions in Elite Female Water Polo: A Retrospective Analysis

OBJECTIVE

Current evidence for concussions is mixed in water polo players. Surveys suggest rates as high as 36%, whereas surveillance studies at international competitions often fail to report them at all. The goal of this study was to examine the incidence of concussions in elite female water polo players from surveillance tools implemented longitudinally.

DESIGN

Retrospective chart analysis of 10 years spanning between 2012 and 2022.

SETTING

National teams or professional sports.

PARTICIPANTS

Female players from the Canadian senior national water polo teams that participated in international competitions and trained more than 10 hours per week in a competitive environment.

ASSESSMENT OF RISK FACTORS

Included player position, recurrence, and time loss before full return to play.

MAIN OUTCOME MEASURES

Prevalence of concussion diagnosis.

RESULTS

Forty-three concussions were identified over the 10 years observed at a median count of 3 concussions per year. Cumulative days lost spanned between 25 and 348 days per team*year. Altogether, this produced a median rate of 14.3 injuries per 100 player*years. Goalkeepers in the sample suffered the highest rates of concussion (25.8%), compared with players in other positions (22.8% of centers and 16.7% of drivers).

CONCLUSIONS

This study found evidence for prevalence of concussions in elite female water polo players. Improved guidelines preceded a significant reduction in time loss after the year 2017. This adds to a body of knowledge suggesting that improved surveillance methods are needed to detect and care for concussions in this population.

Machine-learning-based head impact subtyping based on the spectral densities of the measurable head kinematics

BACKGROUND

Traumatic brain injury can be caused by head impacts, but many brain injury risk estimation models are not equally accurate across the variety of impacts that patients may undergo, and the characteristics of different types of impacts are not well studied. We investigated the spectral characteristics of different head impact types with kinematics classification.

METHODS

Data were analyzed from 3262 head impacts from lab reconstruction, American football, mixed martial arts, and publicly available car crash data. A random forest classifier with spectral densities of linear acceleration and angular velocity was built to classify head impact types (e.g., football, car crash, mixed martial arts). To test the classifier robustness, another 271 lab-reconstructed impacts were obtained from 5 other instrumented mouthguards. Finally, with the classifier, type-specific, nearest-neighbor regression models were built for brain strain.

RESULTS

The classifier reached a median accuracy of 96% over 1000 random partitions of training and test sets. The most important features in the classification included both low- and high-frequency features, both linear acceleration features and angular velocity features. Different head impact types had different distributions of spectral densities in low- and high-frequency ranges (e.g., the spectral densities of mixed martial arts impacts were higher in the high-frequency range than in the low-frequency range). The type-specific regression showed a generally higher R2 value than baseline models without classification.

CONCLUSION

The machine-learning-based classifier enables a better understanding of the impact kinematics spectral density in different sports, and it can be applied to evaluate the quality of impact-simulation systems and on-field data augmentation.

Association Between Serum Neurofilament Light and Glial Fibrillary Acidic Protein Levels and Head Impact Burden in Women's Collegiate Water Polo

Recent investigations have identified water polo athletes as at risk for concussions and repetitive subconcussive head impacts. Head impact exposure in collegiate varsity women's water polo, however, has not yet been longitudinally quantified. We aimed to determine the relationship between cumulative and acute head impact exposure across pre-season training and changes in serum biomarkers of brain injury. Twenty-two Division I collegiate women's water polo players were included in this prospective observational study. They wore sensor-installed mouthguards during all practices and scrimmages during eight weeks of pre-season training. Serum samples were collected at six time points (at baseline, before and after scrimmages during weeks 4 and 7, and after the eight-week pre-season training period) and assayed for neurofilament light (NfL) and glial fibrillary acidic protein (GFAP) using Simoa® Human Neurology 2-Plex B assay kits. Serum GFAP increased over time (e.g., an increase of 0.6559 pg/mL per week; p = 0.0087). Neither longitudinal nor acute pre-post scrimmage changes in GFAP, however, were associated with head impact exposure. Contrarily, an increase in serum NfL across the study period was associated with cumulative head impact magnitude (sum of peak linear acceleration: B = 0.015, SE = 0.006, p = 0.016; sum of peak rotational acceleration: B = 0.148, SE = 0.048, p = 0.006). Acute changes in serum NfL were not associated with head impacts recorded during the two selected scrimmages. Hormonal contraceptive use was associated with lower serum NfL and GFAP levels over time, and elevated salivary levels of progesterone were also associated with lower serum NfL levels. These results suggest that detecting increases in serum NfL may be a useful way to monitor cumulative head impact burden in women's contact sports and that female-specific factors, such as hormonal contraceptive use and circulating progesterone levels, may be neuroprotective, warranting further investigations.

On-Field Deployment and Validation for Wearable Devices

Wearable sensors are an important tool in the study of head acceleration events and head impact injuries in sporting and military activities. Recent advances in sensor technology have improved our understanding of head kinematics during on-field activities; however, proper utilization and interpretation of data from wearable devices requires careful implementation of best practices. The objective of this paper is to summarize minimum requirements and best practices for on-field deployment of wearable devices for the measurement of head acceleration events in vivo to ensure data evaluated are representative of real events and limitations are accurately defined. Best practices covered in this document include the definition of a verified head acceleration event, data windowing, video verification, advanced post-processing techniques, and on-field logistics, as determined through review of the literature and expert opinion. Careful use of best practices, with accurate acknowledgement of limitations, will allow research teams to ensure data evaluated is representative of real events, will improve the robustness of head acceleration event exposure studies, and generally improve the quality and validity of research into head impact injuries.

Injuries Affecting Intercollegiate Water Polo Athletes: A Descriptive Epidemiologic Study

Background

There are few data on injuries suffered by collegiate water polo athletes.

Purpose

To describe the epidemiology of injuries suffered by National College Athletic Association (NCAA) male and female water polo players by using injury surveillance data over a 5-year period.

Study Design

Descriptive epidemiology study.

Methods

Deidentified data on all water polo injuries and illnesses recorded in the Pac-12 Sports Injury Research Archive from July 2016 through June 2021 were obtained and analyzed. Three men's and 4 women's teams were observed for the entire 5-year period, and 1 men's and 1 women's team was observed from July 2018 through June 2021.

Results

During the observation period, 729 injuries were recorded in the database, with no differences in overall injury rates between male and female athletes (relative risk [RR] = 1.0; 95% CI, 0.9-1.2); 33.7% of injuries required a physician encounter, and 3.6% required surgery. The shoulder was the most injured body part, making up 20.6% of all injuries, followed by the head/face (18.8%) and hand/wrist/forearm (11.7%). Shoulder tendinopathy was the most common shoulder injury diagnosis (4.5% of all injuries). Concussion was the most common injury diagnosis overall, making up 11.4% of injuries, and 81.9% of concussions occurred outside of competition. Male athletes were significantly more likely than female athletes to have a concussion in an off-season practice (RR, 3.25; 95% CI, 1.2-8.8) and via contact with another player (RR, 2.9; 95% CI, 1.3-6.4). Half of the 26 surgical procedures occurring over the observation period were for chronic joint trauma of the groin/hip/pelvis/buttock, with 9 of those 13 being for femoroacetabular impingement specifically.

Conclusion

Among NCAA water polo athletes, the shoulder was the most injured body part; however, shoulder injuries rarely required missed time from sport or necessitated surgical intervention. Concussions were the most common injury diagnosis, had the worst return-to-play outcomes among common diagnoses, and were mostly sustained outside of competition. Femoroacetabular impingement was found to be the dominant diagnosis for which surgical intervention was required.

Salivary S100 calcium-binding protein beta (S100B) and neurofilament light (NfL) after acute exposure to repeated head impacts in collegiate water polo players

Blood-based biomarkers of brain injury may be useful for monitoring brain health in athletes at risk for concussions. Two putative biomarkers of sport-related concussion, neurofilament light (NfL), an axonal structural protein, and S100 calcium-binding protein beta (S100B), an astrocyte-derived protein, were measured in saliva, a biofluid which can be sampled in an athletic setting without the risks and burdens associated with blood sampled by venipuncture. Samples were collected from men’s and women’s collegiate water polo players (n = 65) before and after a competitive tournament. Head impacts were measured using sensors previously evaluated for use in water polo, and video recordings were independently reviewed for the purpose of validating impacts recorded by the sensors. Athletes sustained a total of 107 head impacts, all of which were asymptomatic (i.e., no athlete was diagnosed with a concussion or more serious). Post-tournament salivary NfL was directly associated with head impact frequency (RR = 1.151, p = 0.025) and cumulative head impact magnitude (RR = 1.008, p = 0.014), while controlling for baseline salivary NfL. Change in S100B was not associated with head impact exposure (RR < 1.001, p > 0.483). These patterns suggest that repeated head impacts may cause axonal injury, even in asymptomatic athletes.

Head Impact Biomechanics in Youth Flag Football: A Prospective Cohort Study

BACKGROUND

Youth flag football participation has rapidly grown and is a potentially safer alternative to tackle football. However, limited research has quantitatively assessed youth flag football head impact biomechanics.

PURPOSE

To describe head impact biomechanics outcomes in youth flag football and explore factors associated with head impact magnitudes.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

We monitored 52 player-seasons among 48 male flag football players (mean ± SD; age, 9.4 ± 1.1 years; height, 138.6 ± 9.5 cm; mass, 34.7 ± 9.2 kg) across 3 seasons using head impact sensors during practices and games. Sensors recorded head impact frequencies, peak linear (g) and rotational (rad/s²) acceleration, and estimated impact location. Impact rates (IRs) were calculated as 1 impact per 10 player-exposures; IR ratios (IRRs) were used to compare season, event type, and age group IRs; and 95% CIs were calculated for IRs and IRRs. Weekly and seasonal cumulative head impact frequencies and magnitudes were calculated. Mixed-model regression models examined the association between player characteristics, event type, and seasons and peak linear and rotational accelerations.

RESULTS

A total of 429 head impacts from 604 exposures occurred across the study period (IR, 7.10; 95% CI, 4.81-10.50). Weekly and seasonal cumulative median head impact frequencies were 1.00 (range, 0-2.63) and 7.50 (range, 0-21.00), respectively. The most frequent estimated head impact locations were the skull base (n = 96; 22.4%), top of the head (n = 74; 17.2%), and back of the head (n = 66; 15.4%). The combined event type IRs differed among the 3 seasons (IRR range, 1.45-2.68). Games produced greater IRs (IRR, 1.24; 95% CI, 1.01-1.53) and peak linear acceleration (mean difference, 5.69g; P = .008) than did practices. Older players demonstrated greater combined event-type IRs (IRR, 1.46; 95% CI, 1.12-1.90) and increased head impact magnitudes than did younger players, with every 1-year age increase associated with a 3.78g and 602.81-rad/s² increase in peak linear and rotational acceleration magnitude, respectively (P≤ .005).

CONCLUSION

Head IRs and magnitudes varied across seasons, thus highlighting multiple season and cohort data are valuable when providing estimates. Head IRs were relatively low across seasons, while linear and rotational acceleration magnitudes were relatively high.

Head impact exposure and concussion in women's collegiate club lacrosse

This study sought to describe head impact exposure in women's collegiate club lacrosse. Eleven women's collegiate club lacrosse players wore head impact sensors during eight intercollegiate competitions. Video recordings of competitions were used to verify impact data. Athletes completed questionnaires detailing their concussion history and perceived head impact exposure. During the monitored games, no diagnosed concussions were sustained. Three athletes reported sustaining head impacts (median = 0; range: 0-3 impacts per game). Six impacts registered by the sensors were verified on video across a total of 81 athlete-game exposures. Verified impacts had a median peak linear acceleration of 21.0 g (range: 18.3 g - 48.3 g) and peak rotational acceleration of 1.1 krad/s² (range: 0.7 krad/s² - 5.7 krad/s²). Women competing in collegiate club lacrosse are at a low risk of sustaining head impacts, comparable to previous reports of the high school and collegiate varsity levels of play.

A Two-Phased Approach to Quantifying Head Impact Sensor Accuracy: In-Laboratory and On-Field Assessments

Measuring head impacts in sports can further our understanding of brain injury biomechanics and, hopefully, advance concussion diagnostics and prevention. Although there are many head impact sensors available, skepticism on their utility exists over concerns related to measurement error. Previous studies report mixed reliability in head impact sensor measurements, but there is no uniform approach to assessing accuracy, making comparisons between sensors and studies difficult. The objective of this paper is to introduce a two-phased approach to evaluating head impact sensor accuracy. The first phase consists of in-lab impact testing on a dummy headform at varying impact severities under loading conditions representative of each sensor's intended use. We quantify in-lab accuracy by calculating the concordance correlation coefficient (CCC) between a sensor's kinematic measurements and headform reference measurements. For sensors that performed reasonably well in the lab (CCC ≥ 0.80), we completed a second phase of evaluation on-field. Through video validation of impacts measured by sensors on athletes, we classified each sensor measurement as either true-positive and false-positive impact events and computed positive predictive value (PPV) to summarize real-world accuracy. Eight sensors were tested in phase one, but only four sensors were assessed in phase two. Sensor accuracy varied greatly. CCC from phase one ranged from 0.13 to 0.97, with an average value of 0.72. Overall, the four devices that were implemented on-field had PPV that ranged from 16.3 to 91.2%, with an average value of 60.8%. Performance in-lab was not always indicative of the device's performance on-field. The methods proposed in this paper aim to establish a comprehensive approach to the evaluation of sensors so that users can better interpret data collected from athletes.