The incidence rates vary across match play versus training session, seasons (winter vs summer) and playing position (forwards vs backs). The ball carrier has been found to be at greater risk for injury than tacklers. Concussion accounts for 29% of all injuries associated with illegal play, but only 9% of injuries sustained in legal play.
equivalent to a probability (of sustaining a concussion) of between 0.3% and 11.4% for rugby union and of 7.7% and 22.7% for rugby league.
there appears to be a variation in risk of concussion across level of play, with the sub-elite level having the greatest incidence of injury
As hypothesised by Holbourn over 70 years ago, angular acceleration plays an important role in the pathomechanics of concussion, which has major ramifications in terms of helmet design and other efforts to prevent and manage concussion.