The study is part of an international project led by World Rugby to assess the effects of lowering the tackle height in a host of countries, including France, New Zealand and Australia. Researchers found no significant increase in tacklers' heads coming into contact with the ball-carriers' hips or knees, which is associated with an increased risk of head injury assessments and concussion diagnosis. The trial was adopted by Scottish Rugby and made compulsory across all amateur playing levels. Scottish Rugby chief medical officer Dr David Pugh said: "At Scottish Rugby we strive to reduce the incidence of concussion in as many ways as we can. "We are also working with the university on an injury surveillance project, and we hope that this will see a significant drop in concussion rates due to the lower tackle height trial. "Hamish's research clearly demonstrates that player behaviours have changed, reducing head-to-head and head-to-shoulder contacts which should lead to reduced numbers of concussions in our players." In 2023 a study of former rugby players brains by Glasgow University found that out of 31 donated brains analysed, 21 had evidence of a condition linked to repeated head injuries and concussion. A Durham University study last year suggested rugby players who have suffered multiple concussions have biological differences that may make them more prone to developing motor neurone disease (MND) - the condition that former Scottish internationalist Doddie Weir died from. More than 1,000 former amateur and professional rugby union and rugby league players are currently involved in a long-running concussion lawsuit against the sports' governing bodies.