An Instrumented Mouthguard for Real-Time Measurement of Head Kinematics under a Large Range of Sport Specific Accelerations.

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.

Coach perceptions of FA youth heading guidance: an online survey.

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.

Serum neurofilament light concentration does not increase following exposure to low velocity football heading.

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 h, 24 h 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-1 (5.00-7.00 pg · ml-1); 6 h post 6.50 pg · ml-1 (5.70-7.29 pg · ml-1); 24 h post 6.07 pg · ml-1 (5.14-7.01 pg · ml-1); and 7 days post 6.46 pg · ml-1 (5.45-7.46 pg · ml-1)]. 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 reliability and validity of the bar-mounted PUSH BandTM 2.0 during bench press with moderate and heavy loads.

The aim of this study was to assess the reliability and validity of the bar-mounted PUSH BandTM 2.0 to determine peak and mean velocity during the bench press exercise with a moderate (60% one repetition maximum [1RM]) and heavy (90% 1RM) load. We did this by simultaneously recording peak and mean velocity using the PUSH BandTM 2.0 and three-dimensional motion capture from participants bench pressing with 60% and 90% 1RM. We used ordinary least products regression to assess within-session reliability and whether the PUSH BandTM 2.0 could accurately predict motion capture velocity. Results showed that PUSH BandTM 2.0 and motion capture peak and mean velocity reliability was acceptable with both loads. While there was a tendency for the PUSH BandTM 2.0 to slightly overestimate peak and mean velocity, there was no fixed bias. However, mean velocity with 60 and 90% 1RM demonstrated proportional bias (differences between predicted and motion capture values increase with magnitude). Therefore, PUSH BandTM 2.0 peak velocity with 60 and 90% 1RM is valid, but mean velocity is not.

The Validity of the Push Band 2.0 during Vertical Jump Performance.

The Push Band has the potential to provide a cheap and practical method of measuring velocity and power during countermovement vertical jumping (CMJ). However, very little is known about whether it conforms to laboratory-based gold standards. The aim of this study was to assess the agreement between peak and mean velocity and power obtained from the belt-worn Push Band, and derived from three-dimensional motion capture, and vertical force from an in-ground force platform. Twenty-two volunteers performed 3 CMJ on a force platform, while a belt-worn Push Band and a motion capture system (a marker affixed to the Push Band) simultaneously recorded data that enabled peak and mean velocity and power to be calculated and then compared using ordinary least products regression. While the Push Band is reliable, it tends to overestimate peak (9⁻17%) and mean (24⁻27%) velocity, and when compared to force plate-derived peak and mean power, it tends to underestimate (40⁻45%) and demonstrates fixed and proportional bias. This suggests that while the Push Band may provide a useful method for measuring peak and mean velocity during the CMJ, researchers and practitioners should be mindful of its tendency to systematically overestimate and that its measures of peak and mean power should not be used.

Strongman Log Push Press: The Effect Log Diameter has on Force-Time Characteristics.

Renals, L, Lake, J, Keogh, J, and Austin, K. Strongman log push press: The effect log diameter has on force-time characteristics. J Strength Cond Res 32(10): 2693-2700, 2018-Strongman training is becoming more common in strength and conditioning practices, particularly the log press. The existing literature analyzes force characteristics of the log clean and jerk or press compared with the weightlifting clean and jerk exercise. This investigation aims to explore the braking and propulsive phase performance characteristics of the push press with a barbell and strongman logs of different sizes. Ten experienced athletes volunteered to perform the push press exercise using 65% of their 1 repetition maximum using a small-diameter log, a large-diameter log, and a barbell. Analysis of variance showed a significant difference in all mean braking and propulsive characteristics (force, velocity, power, impulse, and displacement) between the barbell and both logs but there was no difference in lift duration. Comparison between both logs showed that the small log had significantly greater power (6%, p = 0.01), velocity (2%, p = 0.01), impulse (5%, p = 0.03), and force (3%, p = 0.01) but no difference in center of mass displacement or lift duration. In addition, propulsive phase when using the barbell was 4.4 times greater in force, 2.2 times in impulse, 1.8 times in velocity, and 2.3 times in power, and this was greater when compared with the larger diameter log. The athletes achieved larger propulsive outputs with a barbell over a log in the push press exercise in addition to showing a higher mechanical demand with a log that increases the larger log diameter, which may mean that the athlete needs to adapt loads when looking to optimize training parameters.