The everyday activities that counted as bursts
Climbing stairs and walking very fast, for example on the way to work, are the researchers' own examples of a burst. In a lab test of 58 adults, walking fast with shopping bags and walking uphill very fast also reached hard effort, taking about 74 seconds on average to get there (Stamatakis, 2022). In 25,241 UK adults who said they didn't exercise, an average of 3 bursts a day of about 1 minute went with a 39% lower risk of dying than no bursts at all. The study watched what people already did, so it can't show the bursts caused the lower risk. The details are below, with how the number of bursts was linked with the risk of dying and how far to trust the numbers. Every number links to its source.
The activities that counted
In the study, a burst was hard effort lasting up to 1 or 2 minutes, done as part of daily life. The researchers give very fast walking, for example while commuting, and climbing stairs as examples (Stamatakis, 2022).
To choose how long a burst should be, they tested 58 adults doing everyday activities (Stamatakis, 2022):
- Walking very fast on the flat
- Walking fast while carrying shopping-like bags
- Walking uphill very fast
People kept going until they met two of three marks for hard effort: a heart rate of at least 77% of their estimated maximum, using at least 64% of their estimated top oxygen intake, or rating the effort at least 15 on a 6-to-20 scale. The heart rate and oxygen marks had to hold for 30 seconds. On average it took about 74 seconds to reach hard effort (Stamatakis, 2022).
That test set the burst length. In the main study, the wrist tracker judged hard effort from how the wrist moved, and almost all the bursts it picked up were short: 92% lasted up to 1 minute (Stamatakis, 2022).
How the number of bursts was linked with the risk of dying
The researchers compared people by how many bursts a wrist tracker picked up each day, against people with no bursts at all (Stamatakis, 2022).
- About 1.5 bursts a day: a 25% lower risk of dying (Stamatakis, 2022).
- 3 bursts a day, the middle value in the group: a 39% lower risk of dying (Stamatakis, 2022).
- More than 3 a day: the risk kept falling, but more slowly. The researchers saw the steepest drops up to about 3 to 4 bursts a day (Stamatakis, 2022).
The researchers added shorter bursts together into 1-minute units, so the numbers are daily averages of those units (Stamatakis, 2022). Only 852 people died during the study, so treat these numbers as rough.
The short version
- In 25,241 UK adults who said they didn't exercise, an average of 3 bursts a day, each about 1 minute of hard effort, went with a 39% lower risk of dying than no bursts (Stamatakis, 2022).
- At 3 bursts a day, the risk of dying from heart and blood vessel disease was 49% lower (Stamatakis, 2022).
- The bursts were part of daily life, like climbing stairs or walking very fast, in people who said they did no exercise in their free time (Stamatakis, 2022).
- In 62,344 people who said they exercised or walked for pleasure more than once a week, short bursts of hard effort went with a similar drop in the risk of dying (Stamatakis, 2022).
The study of 25,241 adults
Stamatakis and colleagues took people in the UK Biobank who said they did no exercise in their free time and went for a walk for pleasure once a week at most. They were 62 on average. Each wore a wrist tracker for a week, and they were followed for about 7 years, during which 852 died (Stamatakis, 2022).
Compared with people who had no bursts at all, the risk of dying was (Stamatakis, 2022):
- 25% lower at about 1.5 bursts a day
- 39% lower at 3 bursts a day
The risk of dying from heart and blood vessel disease was 49% lower at 3 bursts a day (Stamatakis, 2022).
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How far to trust these numbers
- The study watched what people already did. It can't show that adding bursts would lower anyone's risk by these amounts.
- People with more bursts were younger, slimmer and rated their health better. The study adjusted for age, smoking, illness and more, and the results held when people in poor health were left out, but people able to move hard may have been healthier in other ways (Stamatakis, 2022).
- Activity was tracked for one week, about 5.5 years after people said they didn't exercise, so some may have started exercising (Stamatakis, 2022).
- Only about 5.5% of the people invited joined the UK Biobank, so they aren't typical of the UK (Stamatakis, 2022).