RFU tackle height trial ended after concussions rise in Championship Cup
The Rugby Football Union (RFU) has prematurely ended the trial of a new tackle height law after an increase in the number of concussions.
Matches in the Championship Cup were subject to new rules with players not allowed to tackle above the armpit.
But instances of concussion rose among players tackling opponents who were bent at the waist carrying the ball.
The line of the shoulders will again be the permitted tackle height when the knockout stages begin next month.
"We need to analyse the data in more detail, but our preliminary analysis has shown all of these incidents occurred when a bent-at-the-waist tackler was attempting to tackle a bent-at-the-waist ball carrier following a short pass from the scrum half," said RFU interim chief executive Nigel Melville.
"This is an area that the trial was not specifically looking to influence, as the primary focus was to reduce the risk of concussion where ball carrier and tackler were both upright."
The trial, which was due to run for the duration of the competition for second tier sides in England, did succeed in lowering tackle heights.
Tackles above the armpit line went down by 25%, while there was a 41% drop in the number of contacts with the head or neck of a ball carrier.
"This was always a trial and we weren't sure what the outcomes would be," added Melville.
"Our two main objectives were to determine whether, through law change, the height of the tackle can actually be reduced and if a reduction in the height of the tackle then leads to a reduction in concussion risk."
BBC rugby union correspondent Chris Jones
I understand the trial saw approximately a 67% increase in concussions, from an average of 0.6 a game in the regular Championship season, to 1 per match in the Championship Cup.
The number of concussions from upright tackles did fall markedly - as was hoped - but there was a drastic increase in concussive incidents around the breakdown, when both the ball carrier and tackler were bent at the waist.
While the trial was done with the best intentions, it has shown how challenging it will be for administrators to make the professional game safer. There is no quick fix.