Hydrostatic weighing is one way
to measure body fat
December 28, 2004
By Jennifrr Greer
The water is warm. David Ingalls exhales as much air
as he can from his lungs and lowers himself until he’s
completely under water in a 3-foot-by-6-foot tank, legs
crossed. He uses handles on the tank’s sides to
hold his body under the water’s surface and waits
— one ... two ... three seconds.
Ingalls’ goal: to find out how much of his body
is made of fat.
The 53-year-old attorney from Ashland, a serious cyclist,
doesn’t have a problem with excess fat —
the measurement, in fact, shows it makes up 12.7 percent
of his body composition, less than the 15 percent considered
ideal for a man. But he, like many people, likes to
keep tabs on how well his body is functioning.
"I ride several thousand miles a year," said
Ingalls. "I wanted to see what effect that was
having on my body. I took the test two years ago and
the measurements were almost the same."
The underwater measurements, known as hydrostatic weighing,
are among several methods the fitness-inclined can use
to find that number. Other common measurement methods
include skinfold tests and circumference measurements
of the arms, legs and waist.
For athletes and people starting a weight-loss program,
checking body composition can be beneficial, especially
since excess fat is a precursor to many health problems,
said Jenny Slawta, assistant professor of physical education
at Southern Oregon University, where Ingalls’
body fat was measured.
"Overweight is linked to heart disease, diabetes
and recently Alzheimer’s," Slawta said. "Your
body composition can tell you your nutritional status
and can indicate your level of fitness."
Fat is necessary for normal physiological function,
according to Slawta. But stored fat accumulates in organs
and under the skin and in excess leads to health problems
that are predominant in Americans.
What’s too much? Men and women store fat differently.
Women need specific fats for hormone activity and reproduction.
The average male has 25 percent body fat, with 15 being
optimal, Slawta said, while the average female body
is 35 percent fat, with 25 percent being optimal.
All the methods of fat measurement attempt to determine
the ratio of lean body mass — bones, muscles,
tendons, ligaments and water — to fat, but they
take different routes to finding the number.
Clients at health clubs with certified fitness trainers,
for example, will often encounter skinfold tests.
Trainers use calipers to pinch skin at two points on
the arm, just below the shoulder blade and just above
the hip bone to determine body fat, said Alan Zahniser,
a fitness trainer at 24 Hour Fitness in Medford.
"You just pinch the skin from four areas of the
body, add the measurements and use an age chart to determine
the percentage of body fat," Zahniser said.
The test is most accurate, noted Slawta, when it is
accompanied by appropriate calculations.
"There are over 100 variations to use when calculating
with the skinfold method — for instance, using
a chart for menopausal women over the age of 60,"
she said. "There are different charts for many
variations and most of the time only a standard male-
female age chart is used."
Slawta said underwater weighing is one of the most
accurate ways to measure body fat, with an error rate
of 2-4 percent. Some people find the test unnerving,
but not Ingalls.
"The water was warm and Jenny explained everything,"
he said. "She tested me three or four times to
get an accurate reading. I wanted to stay in the tank
when I was done."
Source:www.mailtribune.com
|
