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Contact: Donna Krupa
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Office: (301) 634-7209
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dkrupa@the-aps.org
Oral Contraceptives Impair
Muscle Gains In Young Women
New study looks at effect of oral contraceptive use in
resistance exercise training
NEW ORLEANS—Many active young women use oral contraceptives (OC)
yet its effect on their body composition and exercise performance has not
been thoroughly studied. A team of researchers has now examined the effects
of OC on female muscle mass, and found that oral contraceptive use impairs
muscle gains in young women, and is associated with lower hormone levels.
The findings are contained in a new study entitled Oral Contraceptive
Use Impairs Muscle Gains in Young Women. It was conducted by Chang-Woock
Lee and Steven E. Riechman, Department of Health and Kinesiology, Texas A&M
University, College Station, TX; and Mark A. Newman, Human Energy Research
Laboratory, University of Pittsburgh, Pittsburgh, PA. The researchers will
present their findings at the 122nd Annual Meeting of the American
Physiological Society (APS;
www.the-aps.org/press), which is part of the Experimental Biology 2009
scientific conference. The meeting will be held April 18-22, 2009 in New
Orleans.
The Study
Seventy-three generally healthy women between the ages of 18-31 were
assigned to two groups and completed a 10-week whole-body resistance
exercise training (RET). Group 1 consisted of 34 women who used oral
contraceptives (OC). Group 2 consisted of 39 women who did not take birth
control pills (non-OC). The women were encouraged to consume at least 0.5
grams of protein per pound of body weight per day (a third more than is
called for by the U.S. government nutritional guidelines) to make sure they
consumed enough calories and protein to promote muscle growth.
The participants exercised three times per week for ten weeks under the
supervision of exercise physiologists. They performed a variety of exercises
to include chest press, lat pull down, leg extension, triceps extension,
arm curl and abdominal crunch. Exercise was done using standard exercise
machines and each volunteer performed three sets of 6-10 repetitions per
exercise at 75 percent of their maximum strength. Body composition was
determined using hydrostatic weighing.
Blood samples were taken before and after the training and assessed to
measure anabolic (muscle building) and catabolic (muscle breaking) hormone
levels in blood. Resting and fasting blood concentrations were measured for
three anabolic hormones: DHEA, DHEAS and IGF1.
Findings
The researchers found that:
-
there were significant differences in lean mass gains (OC:
2.1±2.1% vs. non-OC: 3.5±3.2% / OC: 1.0±1.0kg vs. no-OC: 1.6±1.4kg,
p<0.05). However, other muscle responses such as strength gains and
arm/leg circumferences were similar between the OC and non-OC users.
-
resting/fasting blood concentrations of the anabolic
hormones were significantly lower in women taking OC vs. non-OC users
throughout the study period. At the same time, plasma concentrations of
cortisol (catabolic hormone) were elevated.
-
those OC users had reduced DHEA hormone at the end of the
training period. By contrast, the other participants’ levels did not
change.
Conclusion
According to the researchers, “We were surprised at the magnitude of
differences in muscle gains between the two groups, with the non-OC women
gaining more than 60% greater muscle mass than their OC counterpart.” They
added that even though the study has observed negative effects of oral
contraceptive use on muscle gain in the context of resistance exercise
training, “future studies are needed to help explain the reasons behind the
results.”
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Physiology is the study of
how molecules, cells, tissues and organs function to create health or
disease. The American Physiological Society (APS;
www.The-APS.org/press) has been an integral part of this
discovery process since it was established in 1887.
NOTE TO EDITORS: The APS annual meeting is part of the
Experimental Biology 2009 (EB ’09) gathering and will be held April 18-22,
2009 at the New Orleans Convention Center. To schedule an interview with
Mr. Lee or Dr. Riechman, please contact Donna Krupa at
301.634.7209 (office), 703.967.2751 (cell) or
DKrupa@the-APS.org.
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