Background: Head impacts in sports can produce brain injuries. The accurate quantification of head kinematics through instrumented mouthguards (iMG) can help identify underlying brain motion during injurious impacts. The aim of the current study is to assess the validity of an iMG across a large range of linear and rotational accelerations to allow for on-field head impact monitoring. Methods: Drop tests of an instrumented helmeted anthropometric testing device (ATD) were performed across a range of impact magnitudes and locations, with iMG measures collected concurrently. ATD and iMG kinematics were also fed forward to high-fidelity brain models to predict maximal principal strain. Results: The impacts produced a wide range of head kinematics (16–171 g, 1330–10,164 rad/s² and 11.3–41.5 rad/s) and durations (6–18 ms), representing impacts in rugby and boxing. Comparison of the peak values across ATD and iMG indicated high levels of agreement, with a total concordance correlation coefficient of 0.97 for peak impact kinematics and 0.97 for predicted brain strain. We also found good agreement between iMG and ATD measured time-series kinematic data, with the highest normalized root mean squared error for rotational velocity (5.47 ± 2.61%) and the lowest for rotational acceleration (1.24 ± 0.86%). Our results confirm that the iMG can reliably measure laboratory-based head kinematics under a large range of accelerations and is suitable for future on-field validity assessments.

Objectives To investigate if heading frequency and impact biomechanics in a single session influence the concentration of serum neurofilament light (NF-L), a sensitive biomarker for axonal damage, up to 7 days after heading incident at ball velocities reflecting basic training drills. Methods Forty-four males were randomized into either control (n=8), 10 header (n=12), 20 header (n=12) or 40 header (n=12) groups. Linear and angular head accelerations were quantified during heading. Venous blood samples were taken at baseline, 6 hours, 24 hours and 7 days after heading. Serum NF-L was quantified using Quanterix NF-L assay kit on the Simoa HD-1 Platform. Results Serum NF-L did not alter over time (p=0.44) and was not influenced by number of headers [p=0.47; mean(95% CI) concentrations at baseline 6.00 pg/ml (5.00 – 7.00 pg/ml); 6 hours post 6.50 pg/ml (5.70 – 7.29 pg/ml); 24 hours post 6.07 pg/ml (5.14 – 7.01 pg/ml); and 7 days post 6.46 pg/ml (5.45 – 7.46 pg/ml)]. There was no relationship between percentage change in NF-L and summed session linear and angular head accelerations. Conclusion In adult men, heading frequency or impact biomechanics did not affect NF-L response during a single session of headers at ball velocities reflective of basic training tasks.

The popularity of instrumented mouthguards (iMGs) use to measure head impact kinematics in contact sports is growing. To accurately compare between systems, mouthguards should be subjected to standardised laboratory validation testing. The study aimed to establish the validity and reliability of a mouthguard system under independently collected pendulum impactor conditions. A NOCSAE anthropometric testing device with attached mouthguard was impacted in four different locations (front, front boss, rear, rear boss) at four target linear accelerations (25, 50, 75 and 100 g) with two different impactor caps (padded and rigid). Peak linear acceleration, peak rotational velocity and peak rotational acceleration values from the mouthguard were compared against the reference data with a battery of statistical tests, namely R squared values, Lin’s concordance correlation coefficient, intraclass correlation coefficients and Bland Altman analysis. Results indicate the iMG produces valid and reliable data comparable to that of the anthropomorphic testing device reference, with all measured variables reported ‘excellent’ intraclass correlation coefficients above 0.95; concordance correlation coefficients above 0.95; minimal average bias with Bland Altman analysis and R squared values above 0.92 for all measured variables. Results indicate the iMG is appropriately valid and reliable enough to next establish on-field validity.

Concerns surrounding the safety of heading within football led the English Football Association (FA) to implement guidelines for youth football participants in February 2020. Information on coach perceptions of guidelines can help to evaluate their suitability.From aninitial 1383 clubs emailed, a total of 351 respondents from English teams spanning ages U12–U18 completed an online survey between August 2020 and January 2021. Questions included their familiarity with and perceptions of youth guidelines, as well as how they approach heading within training. Information was also gathered on perceived heading frequency within training and matches. 31.1% of respondents were either unaware of guidelines or how they relate to their team. Only 4.8% of respondents did not agree with guidelines. For most respondents (60.1%), heading frequency in training was low (between 0 and 5 headers for the whole team per session), with 71.1% of respondents reporting that heading exposure would stay the same in response to guidelines. Most participants were aware of and agree with FA youth heading guidelines, however the majority think their training will not be influenced by guidelines, questioning their applied usefulness. Regardless of guidelines, coach reported heading frequency within training and matches appears to be low.

Evidence indicates females may be more susceptible to sports-related concussion with worse and prolonged symptom severity according to menstrual cycle phase. We investigated whether menstrual cycle phases influence non-concussive heading kinematics in elite female footballers, and whether these impacts affect an athlete’s cognition. Five eumenorrheic elite female footballers (M _age = 23 ± 4 years) participated in a 16-week proof-of-concept study wherein menstrual cycle phases were tracked, and cognition was monitored. Participants performed a weekly controlled heading drill by heading a ball thrown from 5 m away. Head accelerations were measured using custom-moulded PROTECHT instrumented mouthguards. 256 headers revealed no significant differences in head acceleration across the various phases of the menstrual cycle. However, change in cognitive performance was related to heading completion and menstrual phase. Hormonal fluctuations during the menstrual cycle may influence cognition independent of head impact biomechanics among elite female athletes, under controlled conditions. We note that our study also demonstrated the safety and efficacy of the mouthguard equipment employed here, as well as the ease with which the protocol was received by the athletes. These outcomes should be considered when implementing future research with larger cohorts and the inclusion of match-related heading.