Oral contraceptives impair
muscle gains in young women
Birth
Control
Friday, April 17,
2009
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.
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.
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."
###
American Physiological Society
Thanks to American Physiological
Society for this article.