Sitting for eight or more hours a day can be deadly.
That fact has been hammered home in study after study showing the negative health effects -- including heart disease, poor circulation and joint pain -- associated with being parked on your behind for most of the day. The only sure way to prevent those problems, researchers have said, is to sit far less.
But there is growing evidence that there are ways to reverse the damage without necessarily committing to being on your feet for eight or more hours a day.
A new study by researchers at Indiana University published in Medicine & Science in Sports & Exercise suggests that the impaired blood flow in leg arteries can actually be reversed by breaking up your sitting regimen with five-minute walking breaks.
Sitting can cause blood to pool in the legs and prevent it from effectively flowing to the heart -- a precursor to cardiovascular problems. After just one hour of sitting, normal blood flow became impaired by as much as 50 percent, the study found.
But the men who walked for five minutes on a treadmill for each hour they sat didn't see that decline.
"American adults sit for approximately eight hours a day," Saurabh Thosar, the study's lead author, said in a statement. "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 findings add to a growing body of evidence that all is not lost for people unwilling or unable to get on the standing desk train or those who can't do much about long commutes. It is also the first experimental evidence that moderate movement can promote healthy blood flow, in spite of sitting habits.
Participants in the study were otherwise healthy males between the ages of 20 and 35 who did not have any heath problems like obesity, heart disease, high blood pressure or diabetes.
"They were inactive people though; they did not exercise regularly,” Thosar said in an interview. “There is a risk that people who don’t exercise can start sitting more and more. That’s why we chose that population.”
Going to the gym isn't likely to reverse the damage caused by sitting all day (one study found that six hours of sitting counteracted the positive health benefits of an hour of exercise). But several studies suggest that simply breaking up bouts of sitting with moderate exercise or movement can have a positive impact.
One study earlier this year found that breaking up prolonged sitting with light or moderate walking breaks reduced the blood pressure of a group of obese adults in a randomized trial. And yet another recent study found that breaking up sitting with light activity improved blood sugar levels, but breaking up sitting with bouts of standing did not.
Thosar's study did not investigate whether walking proved more effective than standing when it came to improving blood flow. But he suspects that walking prevented impaired blood flow in the legs because it requires active muscle movement.
"Walking definitely increases blood flow in the legs," added Thosar, who is now a researcher with Oregon Health & Science University. "If it's static and people are not moving, perhaps people are still not using their muscles as much as during walking."
[This post has been updated.]