T he pull-up has long been seen as an important fitness metric. From 1966 to 2013, public middle and high school students in the US were required to do pull-ups as part of the presidential fitness test (an evaluation Donald Trump has considered reinstating). US Marine Corps members were long required to perform pull-ups as part of their regular physical fitness test , and prospective UK Royal Marines must complete a minimum of three to four pull-ups before they are eligible to join. There is no definitive data on how many adults can perform a proper pull-up, but two things are clear: they are very difficult and look extremely cool. “When a new client comes to see me, the most common exercise they say they’d like to be able to do is the pull-up,” says Emily Schofield, a certified personal trainer at the training company Ultimate Performance.…