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.