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Sport, exercise and the menstrual
cycle: where is the research?
G Bruinvels,
1,2,3
R J Burden,
2,3,4
A J McGregor,
5
K E Ackerman,
6
M Dooley,
7
T Richards,
1
C Pedlar
2,6
Despite a decreasing gender gap in exer-
cise participation, there still remains a sig-
nificant under-representation of women
included in sport and exercise medicine
research studies.
1
A review of 1382 sport
and exercise research studies involving
over 6 million participants, from 2011 to
2013, found the representation of women
to be 39%.
1
The complexities of the men-
strual cycle are considered major barriers
to the inclusion of women in clinical
trials.
Historically, partially due to concerns
of potentially damaging unborn fetuses,
medical trials—including drug trials—
were conducted solely in men. Further,
women were perceived as more physiolo-
gically variable, therefore utilising only
male participants would allow meaningful
results with fewer participants and less
funding. Since men were viewed as ade-
quate proxies for women, the years of
exclusion of female participants from
research were considered inconsequential.
However, it is now known that women
can respond very differently to drug
treatments than men. Evidence suggests
that women are almost twice more likely
to have an adverse reaction to a drug
than their male counterparts, and 80% of
drugs withdrawn from the market are
due to unacceptable side effects in
women.
2
When research involving exercise meta-
bolism includes women, participants are
often tested in the early follicular phase of
their menstrual cycle, when hormone
levels are at their lowest, in order to mini-
mise the possible impacts oestradiol and
progesterone may have on the study out-
comes.
3
This type of research practice
leaves much ambiguity around how such
hormones may influence the unique phy-
siological processes in women, from
blood pressure to substrate metabolism,
thus perpetuating the significant gap in
understanding how the menstrual cycle
impacts exercise performance. Sheel
4
recently described a number of sex differ-
ences in the physiological response to
exercise, likely caused in part by ovarian
hormones, highlighting a lack of under-
standing and a need for further research.
We recently reported that 41.7% of
exercising women believe their menstrual
cycle has a negative impact on exercise
training and performance.
5
However,
largely due to the dearth of sports and
exercise research in women, explanations
for this are lacking. Heavy menstrual
bleeding with unknown or undiagnosed
iron deficiency could be a cause but this is
speculative.
There is a clear need to gain better
understanding of female physiology and
to define the effects of the cyclical varia-
tions in hormones, both positive and
negative, on athletic performance. 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.
Twitter Follow Georgie Bruinvels at @gbruinvels and
Richard Burden @rich_burden, Charles Pedlar
@pedlarcr
Contributors GB, RJB, AJM, KEA, MD, TR and CP all
participated in manuscript preparation.
Competing interests None declared.
Provenance and peer review Not commissioned;
externally peer reviewed.
To cite Bruinvels G, Burden RJ, McGregor AJ, et al.
Br J Sports Med Published Online First: [please include
Day Month Year] doi:10.1136/bjsports-2016-096279
Accepted 26 April 2016
Br J Sports Med 2016;0:1.
doi:10.1136/bjsports-2016-096279
REFERENCES
1 Costello JT, Bieuzen F, Bleakley CM. Where are all the
female participants in Sports and Exercise Medicine
research? Eur J Sport Sci 2014;14:847–51.
2 Rademaker M. Do women have more adverse drug
reactions? Am J Clin Dermatol 2001;2:349–51.
3 Oosthuyse T, Bosch AN. The effect of the menstrual
cycle on exercise metabolism: implications for exercise
performance in eumenorrhoeic women. Sports Med
2010;40:207–27.
4 Sheel AW. Sex differences in the physiology of
exercise: an integrative perspective. Exp Physiol
2016;101:211–2.
5 Bruinvels G, Burden R, Brown N, et al. The prevalence
and impact of heavy menstrual bleeding (menorrhagia)
in elite and non-elite athletes. PLoS ONE 2016;11:
e0149881.
1
University College London, London, UK;
2
St Mary’s
University, Twickenham, UK;
3
ORRECO Ltd, Institute of
Technology, Sligo, Ireland;
4
English Institute of Sport,
Loughborough, UK;
5
Brown University, Providence,
Rhode Island, USA;
6
Massachusetts General Hospital,
Boston, Massachusetts, USA;
7
The Poundbury Clinic,
Dorchester, Dorset, UK
Correspondence to G Bruinvels, Division of Surgery
and Interventional Science, University College London,
21 University Street, London WC1E 6AU, UK; georgie.
bruinvels@ucl.ac.uk, @gbruinvels
Bruinvels G, et al.Br J Sports Med Month 2016 Vol 0 No 0 1
Editorial
BJSM Online First, published on June 6, 2016 as 10.1136/bjsports-2016-096279
Copyright Article author (or their employer) 2016. Produced by BMJ Publishing Group Ltd under licence.
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where is the research?
Sport, exercise and the menstrual cycle:
Richards and C Pedlar
G Bruinvels, R J Burden, A J McGregor, K E Ackerman, M Dooley, T
published online June 6, 2016Br J Sports Med
http://bjsm.bmj.com/content/early/2016/05/17/bjsports-2016-096279
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References
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http://bjsm.bmj.com/content/early/2016/05/17/bjsports-2016-096279
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