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Reassuring as they are, the numbers may not be as accurate as he, or any of us, realise.
New research suggests that those who do vigorous activity may be getting more bang for buck than their tracker detects.
Why?
The physical activity guidelines suggest that the dose required for good health is at least 75 minutes a week of vigorous activity or twice that (about 150 minutes) for moderate intensity exercise. This represents a ratio of 1:2, which is what the health metrics of fitness trackers are based on.
The origins of the recommendation are surveys done in the 1990s where respondents reported what activities they did and researchers assigned Metabolic Equivalents of a Task (MET) values.
“The activities they perceived to be ‘moderate’ had an average MET value of about 3.5 METs and the ones they perceived to be vigorous had an average MET value of 7.5,” explains Wendy Brown, a professor Emerita at the University of Queensland and research professor at Bond University.
“So we ‘counted’ every minute of what people reported as vigorous activity as ‘double minutes’ … in health promotion we liked to keep things simple!”
Though Brown, who was involved in developing the Australian physical activity guidelines, explains they did not suggest that the benefits of vigorous versus moderate activity were necessarily in the same ratio, it became the basis for standards used in public health, industry and science.
Self-reporting, however, is inherently imprecise and recent research using accelerometers seemed to suggest that the 1:2 ratio was inaccurate.
For a new study, published in Nature Communications, researchers wanted to answer the question: Instead of a “guesstimate”, what was the true physical activity intensity equivalence? For every minute of vigorous activity, how much moderate activity do we need for the same health benefits?
The team, from the University of Sydney, looked at the accelerometer data of 73,485 adults, aged 40 to 79 years, and followed up with their health outcomes eight years later.
Locky Warner’s workout may be more beneficial than his exercise tracker is giving him credit for.Credit: Ben Searcy Photography
They found the implied health ratio of 1:2, which is then used to calculate a score in the devices used by Warner and hundreds of millions of others around the world, “couldn’t be further from the truth”.
One-minute of vigorous intensity physical activity was equivalent to about 4-to-9 minutes of moderate intensity and 53-to-156 minutes of light intensity for all-cause mortality and cardiometabolic outcomes (heart attacks and strokes, type 2 diabetes, and cardiovascular disease mortality).
“These findings indicate a substantial departure from self-reported estimates and support integrating device-based equivalence into guidelines and wearables,” the authors wrote.
They also demonstrate how potent and time-efficient vigorous activity is, says lead author Emmanuel Stamatakis, a professor of Physical Activity, Lifestyle, and Population Health at the School of Health.
“What a good investment of time it is for people to push it a little in their exercise session”
Emmanuel Stamatakis, lead author and professor at University of Sydney
“What a good investment of time it is for people to push it a little in their exercise session, or incidentally,” adds Stamatakis, also the director of the Mackenzie Wearables Research Hub.
“I have no doubt that vigorous exercise has greater benefits than moderate intensity activity – this is especially true for anything related to the heart and circulation,” says Brown. “There are however some drawbacks to vigorous exercise (for example, injury) so we do have to be careful with health promotion messages on this topic.”
Though Stamatakis hopes that the Physical Activity Guidelines will be updated eventually to reflect the latest evidence, he acknowledges it is a complicated and lengthy process (“Updates happen approximately every 10 years”).
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It is much easier for the technology industry to revise their standards to reward people more accurately for their effort: “It’s quite straightforward for consumer wearables to update their algorithms to incorporate latest knowledge.”
By applying the knowledge, there is a unique opportunity to improve people’s health, he says.
“Consumer wearable devices that provide activity feedback may facilitate behaviour change, and understanding how accumulation across different activity intensities can be used to tailor treatment.”
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