World Rugby want to discover if a minor adjustment can limit the number of collapsed scrums and resets, while also relieving the force on the spine and neck of hookers.

Both hookers must now ensure one foot - the 'brake foot' - is extended towards the opposition during the crouch and bind phases of the engagement sequence. A free-kick will be given if the brake foot is not applied.

The law trial will also be implemented in this year's women's and under-20s Six Nations.

World Rugby chief executive Alan Gilpin said: "We want rugby to be the best it can be for those playing and watching the game and this trial will enable us to understand whether we can positively impact both game and welfare outcomes.

"This builds on voluntary adoption by teams and greater vigilance by match officials in recent elite competitions and we would like to thank Six Nations Rugby and all the participating teams for embracing the trial and we look forward to seeing the results."

Australian Associated Press