It's complicated: sex differences and exercise

One of the most persistent beliefs in human performance is that women lag way behind men when it comes to gaining muscle. But are these hard biological rules or myths? Gosh, I’m glad you asked.

Males do have an advantage when it comes to absolute muscle size compared to females. But the difference is — according to this meta-analysis  — “slight.” Meanwhile, relative increases in muscle size were similar between men and women. One useful perspective from that research is that relative improvements are the same. So, compare two given people and you’ll see that a 10% increase in quad size (for example) will yield the same relative improvement across the board. Not just for beginners and advanced exercisers but for men and women too! This includes post-menopausal women, who experience similar size gains and greater relative strength gains. 

There must be at least one person out there is reading this and thinking “woke feminist propaganda!” Or maybe “luxury gay space communism!” This person is very easy to upset, so I want to assure them that there are still performance differences between men and women. 

Women typically have higher body fat percentages than men. So, even if someone wanted to get extremely lean, the risk is more severe health consequences (including osteoporosis). Meanwhile, those higher body-fat levels are a major driver of performance differences between men and women — and that’s useful to know. When we compare only lean mass, women are very competitive with men for strength. There’s a bigger gap for upper-body strength, which you might expect, but lower-body strength is pretty on par with men when you normalize for body composition. That’s why so many women are great squatters and deadlifters.

Now, let’s examine about a favourite transphobe talking point: muscle architecture. This is a collection of anatomical features, including muscle thickness and attachment points  that theoretically provide men with a huge athletic advantage — and preserve force production across gender transition. Except they don’t. After ~12 months of testosterone, trans men show large increases in muscle size/strength and by ~3 years, their performance often approaches cis men. If an immutable “architectural” advantage existed, this wouldn’t happen.

Athletes are not stock cars — and top performers regularly display huge advantages unrelated to sex. A  common example is humeral retroversion (see below). This might be genetic but it often comes from high volumes of throwing in early childhood. It provides a mechanical advantage when it comes to pitching and/or playing fetch. Humans are complex and their ability to learn, adapt to stresses, and execute complex motor patterns varies wildly. It’s never just one thing. 

There are some other ideas about sex-based differences I want to mention:

Women and fasted training: You may have heard that women respond more poorly to fasted training. It’s possible —  but only short-term studies show this. The bigger risk is low energy availability. Randomized control trials and meta-analyses that match for calories and protein shows equal outcomes between women and men.

Training on your period: There was a while back there where it seemed important to sync up training and your menstrual cycle due to changes in hormones and even heat tolerance (core temperature is a bit higher during the luteal phase). We discussed implementing this practice at Bang but decided that there was too much variability to do this reliably. In other words, a 20% margin of error might offer a theoretical 5% performance improvement. It’s just not worth it.