Motion sensors make sense of physical activity

The motion sensors used in some watches and other fitness devices are providing new, compelling evidence of the role of physical activity in reducing the risk of death.

Previously researchers had to rely on self-reported data on how much sitting and how much exercise people partook, and guess what, they generally exaggerated.

But recently findings have been reported from projects that have fitted research subjects with motion sensors that can accurately report time on the couch against time on the bike or walking.

The results are remarkable: Any time spent moving cuts the risk of death.

A new study from an international team coordinated by the Norway Institute of Health combined data from eight previous studies involving 36,000 subjects wearing motion sensors over six years.

The results suggest strong associations between total physical activity and the risk of dying. This finding was irrespective of the intensity of activity, meaning that increasing the total daily amount of physical activity through light intensity physical activity or moderate to vigorous physical activity substantially contributed to a lower risk of dying.

The observation that light intensity physical activity also provided substantial health benefits is important for public health as this suggests that older people and those who are not able to be physically active at higher intensities will still benefit from just moving around.

The observed associations between physical activity and the risk of death were remarkably stronger than results previously observed when physical activity was assessed by self-reporting participants.

For example, the risk of dying was approximately 60% lower in the most active quarter compared with the least active quarter.

Expressed in absolute numbers per 1,000 participants, 23 individuals died in the most active 25% of participants compared with 130 deaths per 1,000 participants in the least active 25%—more than a five-fold difference between groups.

The study found that moderate to vigorous intensity activity of about 24 minutes per day (a bike trip to work) was associated with the greatest risk reduction.

The study was published in the British Medical Journal.

That study came on the heels of another with similar findings by the Columbia University Vagelos College of Physicians and Surgeons.

That study of around 8,000 middle-aged and older adults found that swapping a half-hour of sitting around with physical activity of any intensity or duration cut the risk of early death by as much as 35 percent.

"Our findings underscore an important public health message that physical activity of any intensity provides health benefits," says Keith Diaz, PhD, lead author of the paper.

The study was published online in the American Journal of Epidemiology.

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