Tackle characteristics associated with concussion in elite men's rugby union: unpicking the differences between tacklers and ball-carriers

Abstract

Objective: To identify characteristics of tackling, of being tackled and interactions between tackle characteristics that are associated with concussion.

Methods: A case-control study in male professional rugby union players in England over five seasons (2016/2017 to 2020/2021) analysed characteristics of tackles that led to a clinically diagnosed concussion (cases), and a control group of tackles that did not result in a concussion. ORs were plotted against the overall frequency of each tackle characteristic.

Results: 231 tackles resulting in concussions (tackler 178, 77%; ball-carrier 53, 23%), alongside 9963 control tackles, were analysed. For tacklers, 'head to torso' (_{Lower CI} OR _{Upper CI; 4.0} 6.5 _10.7) had relatively low odds of concussion compared with 'no head contact'. 'Head to knee' had the highest odds of concussion (_75.3 155.8 _322.4), but 'head to hip' occurred more frequently and had the highest number of concussions per 1000 tackles (3.1/1000 tackles). For ball-carriers, 'head to head' contact had the highest odds of concussion (_56.7 104.3 _192.0). When 'tackler body position' was 'upright', the odds of concussion to the tackler were significantly higher when contacting the ball-carrier's 'head and neck' versus their 'torso' (_3.0 23.7 _206.7).

Conclusions: Lower tackles reduce the chances of concussion to ball-carriers. The influence of tackle height on concussion to tacklers is more nuanced, but the chances are relatively low when contact is made with the ball-carrier's torso. These findings support ongoing implementation of strategies to reduce concussion risk by lowering tackle height to target the torso.

Keywords: Concussion; Male; Sports.

Figure 1. Variable importance plots for Tackler concussions (A) and Ball-Carrier concussions (B) displaying the decrease in model accuracy for classifying concussion (change in out-of-bag (OOB) error) when each variable is excluded. The higher the mean decrease accuracy (MDA) value, the more important the variable is for successful classification. Variables in bold are from Opta data, with the remaining variables derived from bespoke tackle analysis.

Figure 2. Likelihood of concussion for each variable comparing characteristics with the reference (most common) category (y-axis) by the overall frequency of each characteristic (x-axis) for (A) tackler concussion, tackler head contact, (B) ball-carrier concussion, ball-carrier head contact (1=Whiplash injury, 2=Head to upper leg, 4=Head to torso, 5=Head to ground), (C) ball-carrier concussion, tackler head contact (1=Head to ground, 2=Head to lower leg, 3=Head to hip, 4=Head to knee, 5=Head to teammate head, 6=Head to torso, 7=Head to arm, 9=Head to upper leg) and (D) ball-carrier concussion, point of contact on ball-carrier (1=Lower leg, 2=Upper leg, 4=Shoulder and armpit). Characteristics significantly different from the reference category are labelled; characteristics with a number label were not significantly different from the reference category.

Figure 3. Likelihood of concussion to tacklers and ball-carriers according to the first point of contact on the ball-carrier. See online supplemental A for location definitions. Bold text highlights significant difference from the reference category.

Figure 4. Likelihood of concussion for interactions between variables comparing characteristics with the reference (most common) category (y-axis) by the overall frequency of each characteristic (x-axis) for (A) tackler concussion, ball-carrier speed × tackler speed, (B) tackler concussion, tackler body position × point of contact on ball-carrier.