Understanding the Impact of Tackle Height on Tackle Outcomes

Mcknight, Francois

Understanding the Impact of Tackle Height on Tackle Outcomes

Thesis / Dissertation

2026

Publisher

University of Cape Town

Department

Department of Human Biology

Faculty

Faculty of Health Sciences

Abstract

Background: Rugby Union is characterised by the tackle, a frequent, dynamic, physical-technical contest between opposing players. The tackle is responsible for the highest proportion of all injuries, highest injury incidence and highest injury burden compared to other match events. The tackle is also the leading cause of head injuries such as concussion. Reducing head injury and concussion risk, at all levels, is a top priority for rugby stakeholders and governing bodies. Where the tackler makes contact on the ball-carrier (the height of the tackle) has been shown to significantly reduce players' concussion injury risk. To substantiate these findings, lowering the height of a legal tackle from the shoulder to below the bottom of the sternum was trialled. In the wake of these law change trials, new tackle laws have been implemented at the community and junior levels across all major rugby playing nations. For a law change to effectively reduce concussion risk, full compliance with the law changes by all rugby union's stakeholders, including players and coaches, is essential. To increase the likelihood of compliance, demonstrating that the injury prevention intervention may not only improve player safety, but also enhance performance may be required. Objectives: This thesis has two primary objectives. Using a narrative synthesis approach, the first objective was to review all the literature across the rugby football codes (rugby union, rugby league, and rugby sevens) that analysed variable(s) related to the height of the tackle, and injury and performance outcomes. The second objective was to compare the probability of tackle success (the tackler preventing the ball-carrier and ball from progressing towards the tackler try-line) when contacting the ball-carrier at different heights (shoulder, mid-torso, and legs) for different types of tackles (active, passive, smother, and arm) while accounting for other tackler situational factors, within seven playing levels. Methods: For the first objective, the PRISMA guidelines for systematic reviews were followed, and four electronic databases were systematically searched using the relevant keywords. To be eligible, studies had to either assess the area of initial contact on the ball carrier or equipment mimicking a ball-carrier (i.e. tackle dummy) during a tackle; and/or assess the body position of the tackler and/or ball-carrier before (up to 0.5 seconds preceding contact - pre-contact) or during contact (at contact). For second objective, video footage of 271 male rugby union matches were analysed across seven playing groups (Under [U] 12, n=25 matches; U14, n=35; U16, n=39; U18 Amateur n=39; U18 Elite n=38; Senior Amateur, n=40; Senior Elite, n=50) across England, New Zealand, South Africa, Portugal and USA (a total of 52,204 tackles). A logistic regression with type of tackle, tackle direction, first point of contact, tackle sequence, number of tacklers, and attacker intention as explanatory variables and tackle success as the outcome was computed. Post-estimation marginal effects were used to determine the probability of success for the interaction between type of tackle and the height of the first point of contact on the ball-carrier. Results: Eighty studies were included in the narrative review, with the majority focusing on rugby union (63%), followed by rugby league (29%), both codes combined (4%), and rugby sevens (1%). Research predominantly examined male participants (94%), with 6% of female athletes (6%) represented. The main objectives of the included studies related to tackle-related head injuries (n=20, 25%), tackle-related injuries (general) (n=16, 20%), tackle performance (n=13, 16%), tackle technique (n=13, 16%), tackle biomechanics (n=10, 13%), tackle law trial evaluations (n=5, 6%) and describing tackle match demands (n=3, 2%). For the study chapter, the probability of tackle success in relation to where the ball-carrier is contacted varied by tackle type, and within each age group. The probabilities (Pr) for contacting the shoulder vs. mid-torso at the senior levels (elite and amateur) did not differ in relation to tackle success (for instance, for active shoulder tackles within senior elite; shoulder Pr 86% 95% CI 82-89, mid-torso Pr 82% 95% CI 77-86), while at the junior levels contacting the shoulder had a higher probability than other points of contact. Active shoulder tackles had the highest probability of tackle success across the different playing levels across the different contact heights, while arm tackles had the lowest probability (for instance, for mid-torso tackles within senior elite; active Pr 82% 95% CI 77-86 vs. arm Pr 69% 95% CI 64-75). Conclusion: The majority of the reviewed studies used video analysis and anatomical regions to assess where the tackler made contact on the ball-carrier. Tackler and ball-carrier body positions before contact were also used as a proxy to assess the height of the tackle. More than 80% of the studies were conducted on male senior players. While only a few studies evaluated injury and performance within the same study, the general consensus of all the reviewed studies is that contacting the ball-carrier at the mid-torso can reduce the risk of injury and increase the likelihood of a successful performance outcome. In study chapter however, the probability of tackle success in relation to where the ball-carrier is contacted varied by tackle type, and within each age group, highlighting that there are different approaches to ‘win' the tackle contest. Coaches and practitioners can use this information to improve tackle training design and planning within the different age groups, and facilitate player development. From U16 onwards, the probability of tackle success did not differ between active shoulder tackles and smother tackles, suggesting that the ability to execute a safe smother tackle is as important as completing an active shoulder tackle, which is generally the main the focus of tackle training. To advance tackle safety and performance, greater emphasis should be placed on how to perform the smother tackle under the new laws.

Keywords

rugby

tackle

Reference:

Collections

Masters

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