Are Gender Differences in Aerobic Capacity Biological (Back to contents)
The traditional ways of expressing oxygen uptake do not necessarily answer the question of whether gender differences in oxygen uptake are biologically inherent or simply attributable to differencec in muscle size and body composition. This is because statistical "adjustments" do not truly eliminate the gender differences. They only express the criterion trait such as aerobic capacity or muscular strength relative to whatever divisor is used (e.g., body mass, lean body mass, or cross-sectionalmuscle area).
An experimental approach to evaluate this important topic would
be to compare the physiologic responses of males and females who
did not differ in body size, body composition, prior physical
activity, or training history. In this way, there would be no
need to express oxygen consumption as a
ratio score relative to body size or composition. If dividing
the aerobic capacity by body mass or lean body mass truly "adjusts"
for gender differences in aerobic capacity, then matching males
and females on these measures prior to testing for gender differences
would eliminate the body size effects on aerobic capacity. Consequently,
if body size were no longcr a factor because such traits were
matched, then it follows that there should be no gender differences
in aerobic capacity.
In a recent experiment, 10 pairs of sedentary and endurance-trained
males and females were compared for aerobic capacity after matching
for age, stature, body mass, lean body mass, and prior training
history. In addition, aerobic capacity was adjusted for the observed
gender difference in hemoglobin (Hb) concentration. Because part
of the gender difference in aerobic capacity; ln
be explained by differences in Hb concentration, these differences
must be considered when evaluating subsequent Gender differences
in Aerobic capacity.
These differences in aerobic capacity between the genders matched for body mass were 25.3% (sedentary) and 22. 1% (trained). After adjustment for differences in Hb concentration, the gender differences persisted; they were reduced slightly to 18.4% for the sedentary group and 12.8% for the trained group. When the males and females were matched on lean body mass, the gender differences were still substantial; they were 18.4% (sedentary) and 20.5% (trained). When the differences in aerobic capacity were adjusted further for differences in Hb concentration (Adj max Vo2), the gender differences were reduced somewhat, but were still 10.6% (sedentary) and 11.1% (trained).
These results demonstrate that gender differences persist in
aerobic capacity even after matching for body mass, lean body
mass, and Hb concentration. These findings raise the possibility
that gender differences in aerobic capacity reflect traits that
are biologically inherent and unalterable. This is
not to say that such measures cannot be altered with training,
because of course they can; rather, the results suggest that it
may not be appropriate to expect "gender free" differences
in aerobic capacity.