What is the test for the principle of "volenti" in the context of body contact sports?

The key words qualifying the application of the principle of "volenti" are the words "obvious" and "necessary". That is, before the principle applies the risk being assumed must be "obvious", i.e., "foreseeable", and "necessary" for the accomplishment of the purpose of the sport. The risk of falling with resultant injury is both foreseeable and necessary if one is to learn how to ski, skate, ride, tumble, etc. The risk of receiving damaging blows to the body are both foreseeable and necessarily incidental to boxing, football, rugger, hockey and other bodily contact sports if one is to accomplish the various objectives of the game — a knockout, a block, a tackle or a bodycheck — and it is also foreseeable that, from time to time, one will suffer injury from the inadvertent transgressions of the rules of the game: Wooldridge v. Sumner, [1963] 2 Q.B. 43, [1962] 2 All E.R. 978 at 989, "Furthermore, the duty which [the participant] owes is a duty of care, not a duty of skill." Considering the circumstances of the particular sport, the court, in such instances, is simple saying that the participant causing the injury is not negligent, in that he did not breach the standard of care reasonably expected of such participants in such sports. It is in that sense that a fellow participant "accepts the risk" of conduct which would be actionable in other less fractious situations.