What you’ve been told about working out might be wrong, especially if you’re a woman.
Historically, women have been underrepresented in clinical trials and health-based research. Fitness guidelines, it turns out, are no different.
In a recent paper from the University of New South Wales, researchers conducted a review of over 1,500 studies referenced by 11 fitness consensus statements from around the world. These statements—which are used to produce exercise guidelines and recommendations—had all been produced in the last 20 years and included data from over 100 million participants in total.
Of the studies aimed at adults, 70 percent of the participants were male. Two-thirds of the studies only included male participants, while just 12 percent were female only. In older adults, the distribution of data from both sexes was more even, and there were actually slightly more female participants. However, the majority of adult fitness guidelines to date are based on what works best for men.
“There are a bunch of physiological differences between males and females that may mean that best practice exercise prescriptions could differ,” Mandy Hagstrom, a Senior Lecturer in Exercise Physiology at the University of New South Wales and author of this review, told Newsweek.
“For example, females are more fatigue resistant. That could mean that females may need to perform more exercise in a given session to get the same results. Females also take longer to recover from damaging exercise, so perhaps it may make sense for females to have additional rest after these sorts of sessions. However, these questions have not been tested in longer-term exercise intervention studies.”
What we do know is that, physiologically, some distinct differences between biological sexes may influence exercise capacity and strength building. “We have a different physiological environment, including different hormones, and body structures,” Hagstrom said. “For example, females have more type 1 muscle fibers [fibers that produce low power contractions but that are slow to fatigue], smaller lungs, and are of a smaller stature.
“Further, females have multiple variations in their physiology throughout the lifespan such as menarche, pregnancy, and menopause, that may also impact exercise responses differently from the impact that their male counterparts are experiencing at similar life stages.”
This imbalance may be because, until recently, weightlifting was often regarded as a largely male pursuit. This is no longer the case. A recent survey in Australia—where the researchers are based— found that, out of nearly 200,000 participants, women were slightly more likely to meet sufficient levels of muscle-strengthening activity than men. Similar results have been seen in the U.S.
Clearly, more research is needed to understand how workout routines can be tailored to suit women’s bodies. “We need more studies directly examining sex differences in resistance training, particularly in long-term training studies,” Hagstrom said. “We also need more studies that focus solely on female cohorts as this is an understudied area and will help us understand when and if differences between the sexes exist.”
As well as looking at study participants, Hagstrom and her team also analyzed the genders of the authors of the 11 consensus statements. Here, they found a similar discrepancy: only 13 percent of the authors were women, and 91 percent of all first authors were men.
This imbalance not only shows the under-representation of women in research roles, but it may also impact the inclusion of women in the studies themselves. “Research in other fields shows that women authors are more likely to report data by sex, meaning that we can examine if and when differences exist,” Hagstrom said. “There is also research showing that women authors tend to recruit more women into their studies.”
The study’s authors acknowledged that their findings—which were published in the journal Sports Medicine on June 29—were based on binary data which was not representative of all members of society. “It’s worth noting research hasn’t served sex and gender-diverse people well and has tended to use a binary,” Hagstrom said. “We acknowledge that our chosen methods of classifying sex and gender…may have resulted in misclassification of some people.”
While there are many questions left unanswered, this review demonstrates that more work is needed to understand how fitness recommendations could vary between sexes. “The results from our study are important as the first step will help raise awareness around the extent of sex bias in the data that we are relying on,” Hagstrom said. “Many people were likely unaware that we are making so many assumptions when it comes to exercise prescription.
“Now that we know that the guidelines are not considering these factors, hopefully, future guidelines will.”
