DR. JACKIE BUELL: I'm Dr. Jackie Buell, and I do our sports nutrition at Ohio State University,
associated with sports medicine. The iDXA machine, the "DXA" stands for Dual X-ray Absorptiometry
-- so it's a lot easier to say "DXA" -- the machine actually looks at bone density, and
the new generation of the machine can also look at body composition very well. The machine
is not a standard X-ray like we typically think about X-rays, but it does filter the
X-ray energy to two low levels and send it through the person's body in order to sense
how much body composition the person has, including bone, lean mass and body fat. The
iDXA machine gives you about three to four mg. of X-ray energy. To give you an idea of
what that means, a standard chest X-ray would be about 30 to 40 mg. So about a tenth of
a chest X-ray. The iDXA machine is an open table; you lay down flat on your back and
you lay still for, a normal-size person, about seven minutes for the total body scan. And it
has a movement arm that moves over top of your body, about 12 or 18 in. over top of
your body for the entire length of your body to give us the read-outs. In this country,
bone density typically is a test that we do in post-menopausal women to check on their
bone mass as they're going through menopause. Unfortunately, I think it's a little late
to look at it as they're going through menopause. I wish we had a more proactive approach, where
we could look at bone density in young folks to help them understand how to improve that.
By the time you're going through menopause, you can preserve some bone mass, but it's
really hard to improve it. Skin folds and the bod pod are two pretty common -- I'll call
them non-invasive -- techniques right now to do body composition. However, skin folds, we know
are plus or minus 3% in terms of their error, and the bod pod's likely plus or minus 2%
in terms of the error when you start actually using it and doing some research with it.
The iDXA, on the other hand, last study I saw on the iDXA, .5% for lean mass, .5% for
bone and about .8 to .9% for fat mass. When I put somebody on the iDXA, they're able to
compare the lean mass, to see the lean mass in their right arm versus their left arm,
or their right leg versus their left leg. They're able to see the fat mass that we carry
here in our midsection versus what we carry down around our legs. And we think there are
some health issues, some health preventions associated with that. So it's an advantage
to see that kind of data. The machine is also capable of looking at your hip, lumbar, spine
and your forearm bone density. Those are all what we call trabecular bone sites, and we
know that as our hormones change, those sites are more influenced than the other sites that
we call our cortical bones sites. So it's good to have those sites kind of spot-checked
as well, just to know what your bone mass is. Our athletes at OSU often use the machine
-- we put them on there to get their body composition. It depends on who wants to know
their body composition as to where those results go. There are times that it's a female athlete
who might have bone density issues, and we put her on there to see what her bone mass
looks like. But a more common use is to use it with a team, where the coach wants to be
sure that their training routine is doing as they chose it to do, and bringing everybody
down to a normal fat mass, if you will. Dr. Kelsey Logan and I are engaged in some female
athlete triad research where we look at bone density as an outcome of poor fueling and
lack of menstrual cycles. And to look at bone density in female runners is one of the things
we've accomplished here in the last couple years. And then we've done a male runner study
with Dr. Jonathan Scott to look at the bone mass in men as well. And what we see are people
who are running really long mileage and not fueling themselves well probably don't have
the best bone density. It's probably not common for folks to be using the iDXA scan
for body composition as much as we're using it for it here at OSU -- I know a lot of my
exercise science colleagues really believe the iDXA is the way we should be looking at
body composition because of how it looks at body composition. I don't think anybody else
in central Ohio is using an iDXA with this kind of an application. In fact, I work with
people from all over the state who aren't able to find this locally.