How does the level of contact and positional group affect head acceleration rates during training in elite male rugby union players?

Background Concussion incidence has been established during training in elite men’s rugby union, although understanding head acceleration event (HAE) has not.

Objective Describe training HAE using instrumented mouthguards (iMG) in elite men’s rugby union by contact level and positional group.

Design Prospective observational.

Setting Players from professional clubs playing in the highest league in England wore iMG during four-weeks in-season training.

Participants 149 professional male players from six clubs.

Independent Variable Training activity: ‘full-contact’; ‘controlled-contact’; ‘semi-contact’; ‘non-contact’, and positional group: forwards and backs.

Main Outcome HAE count and magnitude (peak linear acceleration, g; peak angular acceleration, rads/s2) were recorded by iMG during video-verified training activities categorised by different levels of contact. HAE frequency was calculated by positional group. Training exposure was calculated from summed durations of training activities where players wore iMG for 20% of the activity length, ensuring HAE capture for its entirety. This was determined by iMG on-teeth proximity sensor. HAE >10g and >1,000rads/s2 were of interest as higher intensity HAE that may be targeted for reduction to protect player welfare.

Results There were 3,437 player activities and 21,918 minutes of training exposure. The incidence of HAE >10g per player minute was 0.12 (95% CI [0.10, 0.14]) in semi-contact, 0.10 [0.09, 0.11] in full-contact, 0.06 [0.06, 0.07] in controlled-contact, 0.02 [0.02, 0.03] in non-contact. The incidence of HAE >1,000rads/s2 per player minute was 0.05 [0.04, 0.05] in semi-contact, 0.04 [0.04, 0.05] in full-contact, 0.03 [0.02, 0.03] in controlled-contact, 0.01 [0.01, 0.01] in non-contact. Forwards experienced one HAE >10g per 16 minutes and >1,000rads/s2 per 17 minutes of training. Backs experienced one HAE >10g per 15 minutes and >1,000rads/s2 per 27 minutes of training.

Conclusion HAE incidence was highest in semi-contact and full-contact training activities. Forwards experienced HAE >1,000rads/s2 more frequently than backs, but experienced similar HAE count >10g.