By Rachael Rettner, Senior Writer
Published: 01/04/2014 07:41 PM EST on LiveScience
News that many female marines in boot camp cannot complete three pull-ups might have you wondering: Why do women find the exercise so difficult?
This week, the Associated Press confirmed that the Marine Corps will delay the implementation of a new standard that would have required women to do at least three pull-ups on their yearly fitness test (the same as the requirement for men). The requirement for women was supposed to go into effect this year, but it was delayed after tests showed that 55 percent of female recruits at a South Carolina site could not complete the task.
Women find pull-ups more difficult than men do because they have less muscle mass in their upper extremities, said Tim Hewett, director of research in the department of sports medicine at Ohio State University Wexner Medical Center. Magnetic resonance imaging (MRI) studies show that women have about 40 percent less upper-body mass than men do, Hewett said. This means that, in general, a woman's natural upper body is only about 50 to 60 percent as strong as a man's, Hewett said. [Men vs. Women: Our Key Physical Differences Explained]
On the other hand, women's lower-body strength is closer to men's. Studies show that a woman's lower extremities are about 80 to 90 percent as strong as a man's, when you take into account body size, Hewett said. Women also have more endurance than men, he said.
"Women do have their [physical] advantages; it's just the one glaring difference in performance is muscle-strength measures, especially in the upper extremities," Hewett said.
Of course, each individual is different, and there are certainly women who can do many pull-ups.
One female Marine said that last year, she could hardly complete a single pull-up, but now, she can do eight, and is working toward her goal of 12, according to Gawker.
And last year, three female Marines became the first to complete the Corps' infantry training, which is considered one of the toughest training courses in the U.S. military.