Women are being excluded from meaningful sport and exercise research because of their periods, a new report suggests.
A review of more than one thousand sport and exercise research studies involving over six million participants between 2011 and 2013 found the representation of women to be just 39%.
In a linked article published in the 'British Journal of Sports Medicine', the researchers said the complexities of the menstrual cycle are considered “major barriers” for clinical trials, so women are often not included.
As a result, women continue to be significantly underrepresented in relevant studies, despite the narrowing gender gap in sports participation.
Historically, women were often left out of research because of fears that drug trials in particular might harm unborn babies, the report explains.
Furthermore, researchers eager to obtain “meaningful results with fewer participants and less funding” didn’t want to risk including women because they were regarded as “more physiologically variable” than men.
“Since men were viewed as adequate proxies for women, the years of exclusion of female participants from research were considered inconsequential,” write the authors.
But it is now known that women respond very differently from men to drugs, and that they are twice as likely to react badly to them.
The report points out that this is important for pharmaceutical companies too, because 80% of the drugs withdrawn from market are due to the “unacceptable side effects” women who took them experienced.
When researchers do include women in trials, they tend to make sure they are in the early follicular phase of their menstrual cycle, when levels of oestrogen and progesterone are at their lowest.
However, this just means that the true impact of these hormones on exercise performance isn’t really known, “thus perpetuating the significant gap in understanding,” argue the authors.
The report highlights that a significant proportion of women athletes believe their menstrual cycle affects their training and worsens performance, but this lack of research means they do not know how to tackle the issue.
"There is a clear need to gain better understanding of the female physiology and to define the effects of the cyclical variations in hormones, both positive and negative, on athletic performance," the authors insist.
"Also, a greater understanding of the menstrual cycle is needed to address the reported negative impacts on exercise training in order to encourage participation and avoid further disparity in gender representation."
The report is published in full in the 'British Journal of Sports Medicine'.