According to a 2010 publication, just over one-third of all visitors to the park climbed Uluru; a high percentage of these were children. A chain handhold added in 1964 and extended in 1976 made the hour-long climb easier, but it remained a steep, hike to the top, where it can be quite windy. It was recommended that individuals drink plenty of water while climbing, and that those who were unfit, or who suffered from vertigo or medical conditions restricting exercise, did not attempt it. Climbing Uluru was generally closed to the public when high winds were present at the top. There were at least 37 deaths relating to recreational climbing since such incidents began being recorded. About one-sixth of visitors made the climb between 2011 and 2015.