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Frequency and duration both play a role in the extent that an intervention to reduce sedentary time can improve cardiometabolic measures, a small randomized trial found.

Compared with uninterrupted sitting, light walking breaks of 5 minutes every half an hour significantly and acutely reduced glucose levels, while taking breaks less frequently -- once an hour -- did not confer such an effect, according to Keith Diaz, PhD, an exercise physiologist at Columbia University Irving Medical Center in New York City, and colleagues.

Meanwhile, drops in systolic blood pressure (BP) were achieved across sedentary break doses tested. Improvements were most prominent with light walks every 60 minutes for 1 minute (-5.2 mm Hg) and every 30 minutes for 5 minutes (-4.3 mm Hg). The magnitude of these BP reductions may translate into a 13% to 15% decrease in risk of cardiovascular disease if sustained over time, the authors reported in the journal .

"What we know now is that for optimal health, you need to move regularly at work, in addition to a daily exercise routine," said Diaz in a . "While that may sound impractical, our findings show that even small amounts of walking spread through the work day can significantly lower your risk of heart disease and other chronic illnesses."

The Physical Activity Guidelines for Americans, last updated in 2018, advised the public that any amount of physical activity is better than none and that there is benefit to increasing moderate to vigorous exercise and reducing time spent sedentary.

However, just how much people need to break from sedentary time was not addressed in the national recommendations.

"Importantly, our findings provide key dosing information necessary for the development of evidence-based quantitative guidelines that describe how often and for how long sedentary breaks should be taken when using light intensity, aerobic-based sedentary breaks," Diaz's group wrote.

"If we hadn't compared multiple options and varied the frequency and duration of the exercise, we would have only been able to provide people with our best guesses of the optimal routine," Diaz added.

The investigators had performed a randomized crossover study that had participants test five different exercise routines, 8 hours at a time, in random order on separate days, including:

• One uninterrupted sedentary control condition
• Light treadmill walks every 30 minutes for 1 minute
• Light treadmill walks every 30 minutes for 5 minutes
• Light treadmill walks every 60 minutes for 1 minute
• Light treadmill walks every 60 minutes for 5 minutes

Out of 25 people screened, 11 who were relatively sedentary, older than 45, and without any pre-existing chronic medical conditions were selected to be randomized.

This cohort averaged 57 years of age; 54.5% were men and 35.3% were Black. The majority were normoglycemic (only one in the pre-diabetic range), and were roughly split between normotensive and prehypertensive/hypertensive at baseline.

Participants abstained from caffeine, alcohol, vitamins/supplements, and exercise for 48 hours prior to study visits and stayed on their usual medications. On the date of study visits, participants arrived in the morning after an overnight fast and had glucose and BP measured every 15 and 60 minutes, respectively.

Diaz's team acknowledged that the study did not analyze the chronic effects of sedentary breaks or more intense physical activity during breaks.

In addition, the small sample was due to the study being terminated early because of the COVID-19 pandemic, they noted.

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