According to a member who knew one of the bodyguards who protects the Prophet, President Hinckley was a very spry and active man, even into his advanced age. One of the most iconic images of President Hinckley is his cane, which he used more often to wave at crowds than to aid his walking.
The story goes that President Hinckley developed very good-natured and mirthful friendships with all of his bodyguards — that is, except for one bodyguard, who took his job very seriously, much to the annoyance of the Prophet. One day, while joking with this serious bodyguard, who showed no response or emotion, President Hinckley decided to show him who’s boss. He took his cane and gave a good, playful thwack to the bodyguard at the back of the knees, causing them to buckle and the bodyguard to tumble to the floor.