When I first started building bicycles for women some 25 years ago, it took only a quick glance at a man and a woman of the same height to see that her legs were longer than his. Her shorter torso was clearly the reason why she felt “stretched out” on a bike and had to endure discomfort in her shoulders and back. So Terry bikes were built with shorter top tubes on all sizes to address this concern.
Around 1990, I decided to get a more analytical and less anecdotal about the root causes of some women’s discomfort while riding. There’s a lot of information about men’s and women’s anatomy and I was looking forward to finding out just how much shorter a woman’s upper body was proportionate to a man’s. Guess what? Women have proportionately longer arms and trunks than men. Looks can be very deceptive, thanks to women’s higher waist lines.
Yet, women’s discomfort on bikes was very real. But what was the underlying cause? We were doing the right thing but for the wrong reason. We needed to know the right reason.
Enter Laura Lund, then working on her Masters in Mechanical Engineering-Bioengineering at Carnegie Mellon University. She did some research and came up with some possible causes for women’s discomfort. In doing so, she confirmed why our designs were working.
So what was going on? It has to do with the distribution of body mass and the location of the center of those masses. They differ between men and women. More of a woman’s body mass is in her trunk than a man’s. And, speaking in simple terms, it’s higher on her trunk than on a man’s. Think of it like this: if you put a five pound weight on your lower back and then bend over, it will be a lot easier than if you bend over with the same weight on your shoulders. Your total weight is the same in both cases, but in the latter case, you’ve moved the center of that weight up and away from the muscles that are doing the work. This higher “center of mass” means more effort is required by the lower back muscles. A similar situation exists in the arms with regard to the forces exerted on the rider’s shoulders.
Add to this the fact that women tend to have smaller muscles than men to support these forces. Not a good scenario!
But the story doesn’t end there. Stay tuned….