Effect of lowering the maximum tackle height in English Schoolboy rugby union on tackle characteristics, and all-injury and concussion rates
Bibliographic record
Abstract
OBJECTIVES: This study compared tackle characteristics and injury incidence in schoolboy rugby union before and after a law change that lowered the maximum legal tackle height. DESIGN: Prospective cohort study. METHODS: Match injuries and game exposures were reported by U15 and U18 schoolboy teams over three seasons (2017/18 to 2019/20) when the legal tackle height was at the line of the shoulder and one season (2021/22) at the line of the armpit. Matches were filmed pre- (U15:11; U18:16 matches) and post- (U15:10; U18:10 matches) tackle height change and tackles were coded for tackler and ball carrier techniques. Tackle characteristic propensities and injury incidences were compared pre- and post-tackle height change using rate ratios (95 % confidence intervals). RESULTS: Pre- to post-tackle height change, the propensity of shoulder height tackles reduced at U15 (rate ratio: 0.62, 95 % confidence interval: 0.51-0.75) and U18 (rate ratio: 0.77, 95 % confidence interval: 0.65-0.92). Post-change, tacklers were more often bent at the waist when tackling at U15 (rate ratio: 1.34, 95 % confidence interval: 1.21-1.49) and U18 (rate ratio: 1.18, 95 % confidence interval: 1.08-1.29). Overall injury incidence pre- and post-tackle height change was not significantly different for U15 (rate ratio: 0.79, 95 % confidence interval: 0.53-1.17) or U18 (rate ratio: 1.11, 95 % confidence interval: 0.89-1.37). Pre- to post-tackle height change, neither all concussions at U15 (rate ratio: 1.43, 95 % confidence interval: 0.73-2.70) and U18 (rate ratio: 0.95, 95 % confidence interval: 0.59-1.47) or tackle-related concussions at U15 (rate ratio: 1.39, 95 % confidence interval: 0.55-3.25) and U18 (rate ratio: 0.92, 95 % confidence interval: 0.48-1.65) were different. CONCLUSIONS: Following a lowering of the permitted tackle height, tackler and ball carrier tackle techniques changed, without changing the incidence of all injuries or concussions. Further lowering of the tackle height may be explored to invoke the necessary technique changes to reduce injury.
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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 | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
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".