A big assumption has kept women out of health and fitness studies for years. What if it’s wrong?

Generations of research on exercise physiology either left out women participants altogether or significantly reduced their numbers in many experiments, leaving us to generalize results from studies that included only or mostly men. (Unsplash+/Getty Images) A big assumption has kept women out of health and fitness studies for years. What if it’s wrong? Published: September 7, 2026 8.37am EDT Share article Print article What if much of what we thought we knew about women’s health and fitness was suddenly called into question? Researchers in many fields of science, including my area of exercise physiology, are facing this scenario, after generations of research that either left out women participants altogether or significantly reduced their numbers in countless experiments. These practices have continued to inform, perhaps mistakenly, our understanding of issues ranging from athletic performance to the benefits of exercise, where we have been left to presume it was OK to generalize results from testing men as if they applied to women and men equally. These are not just old studies from back in the day when women were routinely excluded from many arenas. These are also studies from the past 20 years, when many people thought research was finally catching up. Now that barriers to the inclusion of women in research studies are being addressed, researchers can start to broaden their work. (Unsplash+/Hush Naidoo Jade Photography) Why women were left out of research studies Leaving women out of scientific studies has largely been the result of uncertainty over how to account for potential fluctuations related to menstruation or hormonal birth control. Not knowing how or whether these factors might affect, for example, muscle function, researchers simply included fewer women in their research, or didn’t include them at all, based on assumptions that turned out to be incorrect. It’s hardly the first time. We look back to the times before women were allowed to complete in the Olympics, for example, when women were discouraged from participating in sports because it might damage their bodies or have negative outcomes for reproduction. A particular piece of modern research broke the logjam in my field: the finding that menstrual cycles typically do not have significant impact on blood vessel function, nor are there meaningful muscle and performance differences between women who are using hormonal birth control and those who are not. Those results helped…