Being able to do pull-ups, or even a pull-up, is difficult and frustrating for many people, especially for women and tall men.

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When I was young, fit, and an aspiring rock climber I spent a good deal of time and mental energy one year pitting myself against the bar one of my housemates had mounted in one of the doorframes, and I took it as a personal failure as the move continued to elude me.

I mumbled about having less upper body strength, but still thought that if I just kept working out it would make up the difference. But according to Tara Parker-Pope I was wrong and unnecessarily guilting myself.

Being able to do pull-ups, it turns out, has at least as much to do with Physics 101 and percentage of body fat as it does to do with Upper Body Training 101.

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Citing a recent study led by Paul Vanderburgh, professor of exercise physiology and associate provost and dean at the University of Dayton, which found an intensive program of upper body strength training was remarkably ineffective for increasing a group of women’s ability to do a pull-up, Parker-Pope explains.

Men and women who can do pull-ups tend to have short arms, low body fat, and strength. Arm length is important because shorter levers (upper arms) are more efficient than longer ones.

Short of surgery we are stuck with the arms we got, so tall men with long arms have a harder time than shorter men with shorter arms do. But, in general, men have an easier time building muscle (good old testosterone) and can achieve lower body fat percentages (4% vs. 10%+ for the typical fit woman) so they tend to have a better chance at reaching the bar than women do.

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The pull-up is a killer. Doing it properly makes it even harder. But there’s method to this madness – massive gains!