It is widely known that sitting for prolonged periods of time can have adverse health effects. But a new study published in the British Journal of Sports Medicine suggests that shortening the amount of time spent sitting could protect aging DNA and even prolong lifespan, Medical News Today reports.

Previous studies reported by Medical News Today have suggested that individuals who spend less time sitting have a lower risk for chronic diseases - such as diabetes, stroke, breast and colon cancer - and a lower risk for heart failure.

But researchers from this latest study looked at how physical activity lengthens telomeres. Telomeres sit on the "DNA storage units" of each cell, called chromosomes, and stop them from unraveling or clumping together and "scrambling" the genetic codes they contain.

In this way, telomeres are similar to the plastic tips on the end of shoelaces, protecting the string-like chromosomes, say the researchers.

"There is growing concern that not only low physical activity level in populations, but probably also sitting and sedentary behavior, is an important and new health hazard of our time," write the researchers, who investigated whether physical activity affects telomere length.

Twice in 6-month increments, the team analyzed the telomere length in the blood cells of 49 sedentary and overweight people in their late 60s. All participants were part of a previous clinical trial that randomly separated them into two groups: those assigned to a 6-month exercise program and those who were left to do as they pleased.

During this time, researchers tracked their physical activity levels with a 7-day diary and a pedometer that measured the number of steps they took each day. The amount of time they spent sitting each day was reported through a questionnaire.

The participants in the exercise program group experienced an increase in time spent exercising and number of steps taken daily, but the amount of time spent seated decreased in both groups.

The researchers say increases in physical activity, however, had less of an impact than reductions in sitting time; reduced sitting time in the exercise group was linked to telomere lengthening in blood cells.

The team notes that the number of daily steps taken was not linked to changes in telomere length, but increased moderate intensity physical activity was linked to shortened telomere length - though the researchers say this was not significant.

Based on the findings of their study, they hypothesize that reducing sitting hours is more important than increasing exercise time for elderly risk individuals.