820 FO54 – The effectiveness of lowering the legal tackle height (shoulder to armpit) in English schoolboy rugby union injuries
Bibliographic record
Abstract
Background Rugby union (‘rugby’) is a high-intensity collision sport with a high risk of injury, particularly in the tackle. Injury prevention strategies including policy changes are required to minimise the risk. Objective Compare tackle characteristics and injury incidence in schoolboy rugby pre- and post-tackle height change. Design Prospective cohort study. Setting English schoolboy rugby. Participants U15 and U18 teams from 36 schools. Intervention Reduction of the legal tackle height from the shoulder (2017/18 to 2019/20 playing seasons) to the armpit (2021/22 playing season). Main Outcome Measures Propensity of tackle characteristics/1000 tackles. Injury incidence/1000 player match hours and rate ratios (RR) pre- and post-intervention. Results From pre- to post-tackle height change, the propensity of tackles made at shoulder height was reduced at U15 (pre: 140.5/1000 tackles vs post: 86.8/1000 tackles; RR: 0.62, 95%CI: 0.51–0.75; P<0.001) and U18 (pre: 124.1/1000 tackles vs post: 44.4/1000 tackles; RR: 0.36, 95%CI: 0.28–0.45; P<0.001). Lower limb height tackles increased in U15 (pre: 28.5/1000 tackles vs post: 41.8/1000 tackles; rate ratio: 1.45, 95%CI: 1.03–2.10, P=0.03) and U18 age groups (pre: 40.3/1000 tackles vs post: 144.4/1000 tackles; rate ratio: 3.58, 95%CI: 2.88–4.48; P<0.001). The overall injury incidence pre- and post-tackle height change was not significantly different for either U15 (pre: 24.6/1000 player match hours vs post: 19.5/1000 player match hours; RR: 0.79, 95%CI: 0.53–1.17) or U18 (pre: 34.6/1000 player match hours vs post: 38.3/1000 player match hours; RR: 1.11, 95%CI: 0.89–1.37). Concussions were not significantly different pre- to post-tackle height change in U15 (pre: 6.4/1000 player match hours vs post: 9.2/1000 player match hours; RR: 1.43, 95%CI: 0.73–2.70) or U18 (pre: 9.2/1000 player match hours vs post: 8.7/1000 player match hours; RR: 0.95, 95%CI: 0.59–1.47). Conclusions A change in the permitted tackle height changed tackling behaviour, but this did not reduce the incidence of all injuries or concussions.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.010 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.003 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.008 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".