Two-minute walk every hour may reduce hazard of prolonged sitting

Numerous studies have shown that prolonged sitting day after day is linked to poorer health and early death. Now, a new study suggests even a small change can make a difference. The researchers say a 2-minute walk every hour may offset the risk of death linked to prolonged sitting.

New research suggests a 2-minute stroll every hour may offset the risk of death linked to prolonged sitting.

The researchers report their study in the Clinical Journal of the American Society of Nephrology (CJASN).

They conclude that low-intensity activity such as standing may not be enough to offset the effect of sitting for long periods, but adding just 2 minutes of walking per hour to a weekly routine of more moderate exercise may have an effect.

Previous studies have linked daily prolonged sitting to increased risk of premature death, as well as heart disease, diabetes and other chronic health problems.

To reduce these risks, bodies like the American Heart Association recommend adults do at least 150 minutes a week of moderate-intensity exercise, or 75 minutes a week of vigorous exercise.

However, the researchers note that 80% of Americans do not achieve this recommendation, so they wondered if there might be more achievable goals - what kinds of brief, light activities might be traded for some of the sitting time - that could make a difference?

For their analysis, the research team used data on 3,243 participants in the 2003-04 National Health and Nutrition Examination Survey (NHANES). To monitor the intensity of their activity during waking hours, the survey had asked participants to wear accelerometers for several days.

The participants were followed for 3 years after the activity data was collected. During this time 137 of them died.

2 minutes of walking per hour linked to 33% lower risk of death

On the basis of the accelerometer readings, the researchers worked out on average how many minutes per hour were spent on sedentary (less than 100 accelerometer counts per minute), low (100-499), light (500-2019), and moderate to vigorous (2020 and over) activity.

They then examined links with mortality of 2 minutes per hour less of sedentary time spent in one of the low, light, or moderate/vigorous activity durations.

The researchers found no benefit to decreasing sitting by 2 minutes per hour and replacing it with 2 minutes of low-intensity activity, such as standing.

However, they found trading 2 minutes of sitting for 2 minutes of light-intensity activity - such as casual walking, light gardening or cleaning - was linked to a 33% lower risk of premature death.

The researchers at the University of Utah School of Medicine in Salt Lake City, say:

"It was fascinating to see the results because the current national focus is on moderate or vigorous activity. To see that light activity had an association with lower mortality is intriguing."

Even short periods of light activity add up

The researchers note that even short periods of light activity add up to a lot when repeated over the course of a week. Assuming you are awake for 16 hours a day, then strolling for 2 minutes an hour adds 400 kcal a week to your energy expenditure - which is not far off the 600 kcal it takes to accomplish the goal of moderate exercise. 

"Based on these results we would recommend adding 2 minutes of walking each hour in combination with normal activities, which should include 2.5 hours of moderate exercise each week."

In fact, moderate exercise brings health benefits in ways that light exercise cannot - for example, it strengthens the heart, muscles and bones.

Because of its design, this type of study cannot prove that doing 2 minutes of light activity an hour reduces risk of premature death - it can only show links to it and "strongly suggest."

The research team says only large, randomized interventional trials can show if replacing some sitting time with light activity leads to better health.

The National Institute of Diabetes and Digestive Kidney Diseases (NIDDK) and the University of Utah Study Design and Biostatistics Center helped to fund the study.

References:

1.  Light-intensity physical activities and mortality in the United States general population and CKD subpopulation, Srinivasan Beddhu, et al., Clinical Journal of the American Society of Nephrology, doi:10.2215/​ CJN.08410814, published online 30 April 2015, abstract.
2.  University of Utah Health Care news release, accessed 5 May 2015.