Regular walking breaks 'protect arteries'

“Just a five-minute walk every hour helps protect against damage of sitting all day,” the Mail Online reports.

A study of 12 healthy but inactive young men found that if they sat still without moving their legs for three hours, the walls of their main leg artery showed signs of decreased flexibility. However, this was “prevented” if the men took five-minute light walking breaks about every hour.

Less flexibility in the walls of the arteries has been linked to atherosclerosis (hardening and narrowing of the arteries), which increases the risk of heart disease.

However, it is not possible to say from this small and short-term study whether taking walking breaks would definitely reduce a person’s risk of heart disease.

There is a growing body of evidence that spending more time in sedentary behaviour such as sitting can have adverse health effects – for example, a 2014 study found a link between sedentary behaviour and increased risk of chronic diseases.

While this study may not be definitive proof of the benefits of short breaks during periods of inactivity, having such breaks isn’t harmful, and could turn out to be beneficial.

What kind of research was this?

This was a small crossover randomised controlled trial (RCT) assessing the effect of breaks in sitting time on one measure of cardiovascular disease risk: flexibility of the walls of arteries.

The researchers report that sitting for long periods of time has been associated with increased risk of chronic diseases and death, and this may be independent of how physically active a person is when they are not sitting. This is arguably more an issue now than it would have been in the past, as a lot of us have jobs where sitting (sedentary behaviour) is the norm.

Short breaks from sitting are reported to be associated with improvements in a lower waist circumference, and fats and sugar in the blood.

A randomised controlled trial is the best way to assess the impact of an intervention on outcomes.


What were the basic results?

The researchers found that the widening of the artery in response to blood flow (called flow-mediated dilation) reduced over three hours spent sitting without moving. However, getting up for five-minute walks in this period stopped this from happening. The researchers did not find any difference between the trials in another measure of what is going on in the arteries, called the “shear rate” (a measurement of how well a fluid flows through a channel such as a blood vessel).


Conclusion

This small and very short-term crossover randomised controlled trial has suggested that sitting still for long periods of time causes the walls of the main artery in the leg to become less flexible, and that having five-minute walking breaks about every hour can prevent this.

The big question is: does this have any effect on our health?

The flexibility of arteries (or in this case, one particular artery) is used as what is called a “proxy” or “surrogate” marker for a person’s risk of cardiovascular disease. However, just because these surrogate markers improve, this does not guarantee that a person will have a lower risk of cardiovascular disease. Longer-term trials are needed to determine this.

The potential adverse effects of spending a lot of time sitting, independent of a person’s physical activity, is currently a popular area of study. Standing desks are becoming increasingly popular in the US, so people spend most of their working day on their feet. Some even bring a treadmill into their office (see this recent BBC News report on desk treadmills).

Researchers are particularly interested in whether taking breaks from unavoidable periods of sitting could potentially reduce any adverse effects, but this research is still at an early stage.
http://www.nhs.uk/news/2014/09September/Pages/Regular-walking-breaks-protects-arteries.aspx