The Effect of Changing Weekly Contact Training Duration Beyond Current Guidelines on Head Acceleration Events in Rugby Union

Background: This study simulated the effect of reducing contact training duration on overall in-season head acceleration event (HAE) exposure within men’s and women’s rugby union. Methods: Players (n = 982) from two professional men’s and two semi-professional women’s competitions wore instrumented mouthguards in training and match-play for one season. Generalised linear mixed models were used to estimate the in-season weekly HAE exposures per position, sex and contact type. Simulation of modelled estimates evaluated the impact of reducing contact load guidelines by 25%, 50% and 75% (scenario 1), and replacing full contact training with controlled contact (scenario 2) or non-contact (scenario 3) training for different seasonal match exposures. Previously established contact load guidelines were used as a reference point. Results: HAEs were decreased by a maximum of 3.2 per week (0–95 HAEs per season; 0–23%). In scenario 1, the decrease in HAEs was disproportionately smaller than the reduction in contact training duration (e.g. 23.7% reduction in overall rugby minutes for 7% decrease in HAEs). Scenario 2 decreased HAEs similarly to scenario 1 but with no reduction in contact time. Scenario 3 decreased HAEs proportionally with contact time reductions (e.g. 8.9% decrease in HAEs >10 g for 9.6% reduction in overall rugby minutes). Conclusions: HAEs were reduced in all scenarios, but the reduction was relatively small due to the low overall rate of HAEs in training. Policymakers should be aware of the tradeoffs involved in any change. Managing individuals with higher HAE exposures may be more appropriate than reducing contact training guidelines.