By Dr. Jack Rutherford
Pull-ups have been around for years and are used by many groups such as the U.S. Armed Forces and the President’s Council on Physical Fitness and Sports as a measure of fitness. Pull-ups are performed by placing your hands with an overhand grip on a raised bar, then using your back and arm muscles to pull yourself up until your chin passes the bar. (Chin-ups are the exact same exercise using an underhand grip). After lowering the body down until the arms are straight, the exercise is repeated as many times as possible.
A male recruit in the Marines should be able to do at least 3 pull-ups or chin-ups. A female recruit is not required to do them. On the national fitness test for youth, the President’s Challenge, 14 year-old boys can reach the highest performance level by doing 10 pull-ups; for 14 year-old girls, it’s only 2.
So why can’t girls and women do pull-ups. As it turns out, this is an area of personal interest to me. In 1992, I wrote an entire doctoral dissertation on the subject.
In my study, I recruited college-age women and trained them for 12 weeks. The training was carefully designed to develop the musculature needed to perform pull-ups. Specifically, the training program included machine-assisted pull-ups, lat pull-downs, and biceps curls, among other exercises. I tested their ability to perform pull-ups before and after the 12 week program and here’s what I found. Even after three months of upper body strength training, most women still couldn’t do one pull-up. And yet, their upper body strength as measured by a pull-up actually doubled during that period.
Here’s how I measured that. I used specific joint angles to determine what percentage of one pull-up had been achieved. For example, if the subject’s elbow joint flexed to 90 degrees during the pull-up, but no further, they achieved one-half a pull-up. A 45-degree joint angle meant 75 percent of one pull-up and so on.
At the beginning of the study, the women could do only 40 percent of one pull-up on the average. At the half-way point of the study (six weeks), they were able to do 60 percent of a pull-up. At the end of the study, they reached the 80 percent level. So they doubled their strength but could still not do a single pull-up.
Interestingly, a recent study at the University of Dayton found similar results. In this study, researchers took 17 normal-weight women who could not do a single pull-up and trained them three days a week for three months. On testing day, only 4 of the 17 women were successful at performing a single pull-up.
“We honestly thought we could get everyone to do one,” said Paul Vanderburgh, a professor of exercise physiology at the University of Dayton and an author on the study.
One of the reasons women fare worse on pull-ups is that they have generally higher levels of body fat. Males maintain 5 to 10 percent less body fat on average, which means their strength per pound of body weight ratio is higher. The more strength per pound a person has, the easier it will be to lift that weight. Another reason is that because of their lower levels of testosterone, women don’t develop as much muscle tissue as men during training. Strength is determined largely by the cross-sectional area of the working muscles. In other words, bigger muscles equal stronger muscles.
However, just because a woman can’t do a pull-up doesn’t mean she’s not fit. It may just be that the test doesn’t reflect the improvement.