from : Saurabh Thosar
BLOOMINGTON, Ind. -- An Indiana University study has found that three
easy -- one could even say slow -- 5-minute walks can reverse harm
caused to leg arteries during three hours of prolonged sitting.
Sitting for long periods of time, like many people do daily at their
jobs, is associated with risk factors such as higher cholesterol levels
and greater waist circumference that can lead to cardiovascular and
metabolic disease. When people sit, slack muscles do not contract to
effectively pump blood to the heart. Blood can pool in the legs and
affect the endothelial function of arteries, or the ability of blood
vessels to expand from increased blood flow.
This study is the first experimental evidence of these effects, said
Saurabh Thosar, a postdoctoral researcher at Oregon Health &
Science University, who led the study as a doctoral candidate at IU's
School of Public Health-Bloomington.
"There is plenty of epidemiological evidence linking sitting time to
various chronic diseases and linking breaking sitting time to
beneficial cardiovascular effects, but there is very little experimental
evidence," Thosar said. "We have shown that prolonged sitting impairs
endothelial function, which is an early marker of cardiovascular
disease, and that breaking sitting time prevents the decline in that
The researchers were able to demonstrate that during a three-hour
period, the flow-mediated dilation, or the expansion of the arteries as a
result of increased blood flow, of the main artery in the legs was
impaired by as much as 50 percent after just one hour. The study
participants who walked for 5 minutes each hour of sitting saw their
arterial function stay the same -- it did not drop throughout the
three-hour period. Thosar says it is likely that the increase in muscle
activity and blood flow accounts for this.
"American adults sit for approximately eight hours a day," he said.
"The impairment in endothelial function is significant after just one
hour of sitting. It is interesting to see that light physical activity
can help in preventing this impairment."
The study involved 11 non-obese, healthy men between the ages of
20-35 who participated in two randomized trials. In one trial they sat
for three hours without moving their legs. Researchers used a blood
pressure cuff and ultrasound technology to measure the functionality of
the femoral artery at baseline and again at the one-, two- and
In the second trial, the men sat during a three-hour period but also
walked on a treadmill for 5 minutes at a speed of 2 mph at the
30-minute mark, 1.5-hour mark and 2.5-hour mark. Researchers measured
the functionality of the femoral artery at the same intervals as in the