A tackler correctly adhering to the tackle instruction in a front-on, one-on-one torso tackle alters the peak inertial head kinematics of the ball carrier but not the tackler.

Objectives: To evaluate if the tackler correctly adhering, or not, to four different instructions of legal front-on one-on-one torso tackles altered the tackler and/or ball carrier peak inertial head kinematics.
Design: Controlled laboratory study.
Methods: Fifteen rugby-code players measured with three-dimensional optoelectronic motion capture performed two tackle instructions from the Australian National Rugby League coaching manual on under (Dominant National Rugby League) and over (Smother National Rugby League) the ball tackles, and two novel variants of these (under, Dominant, Torso Stick; over, Smother, Pop, Lock). A series of mixed general linear models identified if the tackler adhering (n = 455), or not (n = 139) to the tackle instructions altered peak inertial head kinematics.
Results: The tackler's peak inertial head kinematics did not significantly change whether or not they adhered to each of the tackle instructions. When the tackler did adhere to the instructions, the ball carrier sustained a lower peak inertial head kinematics (p < 0.01) in the Smother National Rugby League tackle but higher peak inertial head kinematics in the Smother, Pop, Lock.
Conclusions: The ball carriers' inertial head kinematics but not the tacklers were increased when the tackler adhered to this study's variants of the over and under the ball tackle instructions, suggesting that the tacklers were more effective in their tackle performance than the traditional tackle instructions when adhering to the tackle instruction. Greater adherence to the under the ball instructions suggests that the over the ball instruction is a more challenging technique to learn.
Competing Interests: Declaration of interest statement Suzi Edwards declares that they have no conflict of interest. Andrew Gardner, Ph.D. has a clinical practice in neuropsychology involving individuals who have sustained sport-related concussion (including current and former athletes). He has been a contracted concussion consultant to Rugby Australia (2016–). He has received travel funding or been reimbursed by professional sporting bodies, and commercial organisations for discussing or presenting sport-related concussion research at meetings, scientific conferences, workshops, and symposiums. He has received research funding from the National Rugby League (NRL) for the Retired Players Brain Health research programme. Previous grant funding includes the NSW Sporting Injuries Committee, the Brain Foundation (Australia), an Australian–American Fulbright Commission Postdoctoral Award, a Hunter New England Local Health District, Research, Innovation and Partnerships Health Research & Translation Centre and Clinical Research Fellowship Scheme, and the Hunter Medical Research Institute (HMRI), supported by Jennie Thomas, and the HMRI, supported by Anne Greaves. He has served as a scientific advisor for hitIQ Ltd. Ross Tucker is a research consultant to World Rugby (Pty) Ltd, the governing body for Rugby Union globally. Ken Quarrie is employed as the senior sport scientist for New Zealand Rugby. Grant Iverson serves as a scientific advisor for NanoDx™ (formerly BioDirection, Inc.), Sway Operations, LLC, and Highmark, Inc. He has a clinical and consulting practice in forensic neuropsychology, including expert testimony, involving individuals who have sustained mild TBIs (including athletes). He has received research funding from several test publishing companies, including ImPACT Applications, Inc., CNS Vital Signs, and Psychological Assessment Resources (PAR, Inc.). He has received research funding as a principal investigator from the National Football League, and salary support as a collaborator from the Harvard Integrated Program to Protect and Improve the Health of National Football League Players Association Members. Gary Strangman has received pilot research funding from the Harvard Football Player's Health Study, funded through the National Football League Players Association.
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