If you sit all day, you need 60 to exercise for minutes
RESEARCHERS ARRIVED AT THEIR FINDINGS BY ANALYSING DATA FROM 16 STUDIES INVOLVING MORE THAN A MILLION PEOPLE
O ffice workers and others who for sit eight hours a day can avoid the health risks associated with that inactivity by doing an hour of physical activity a day, a new study suggests.
The research team behind the study wanted to know if it was possible for people who sit all day at an office job to compensate for the harmful effects of that lack of activity by getting some exercise. In short, the answer is yes.
Researchers arrived at their findings by analysing data from 16 studies involving more than a million people. They found that people who were physically active, but sat for eight hours a day, had a much lower risk of death compared to people who weren’t physically active, even if they sat for fewer hours.
“This suggests that physical activity is particularly important, no matter how many hours a day are spent sitting,” the study’s authors said.
The researchers found that doing at least one hour a day of physical activity was enough to completely offset the increased risk of death from doing all that sitting.
Crucial to be active
By physical activity, researchers said walking at 5.6 km/h meets the standard, as would cycling at 16 km/h.
“Our message is a positive one: it is possible to reduce — or even eliminate — these risks if we are active enough, even without having to take up sports or go to the gym,” said lead author Ulf Ekelung, a professor at the Norwegian School of Sports Sciences and the University of Cambridge.
That message was welcome news for Toronto lawyer Kiran Gill, who often bikes to and from work. “I am surprised it only takes one hour to mitigate the effects of eight hours of sitting. I would think that would take a lot more,” she said.
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While an hour of day of physical activity is ideal, researchers said getting less than an hour of daily exercise can still reduce the health risks of sitting for hours.
The key message from the study is that if long periods of sitting each day can’t be avoided, it’s crucial to be physically active.
Researchers also looked at the health risks of one particular type of sedentary activity — watching a lot of television.
They found that those who sat and watched at least three hours of TV per day had an increased risk of death for all groups, except those who en- gaged in moderately intensive physical activity for 60 to 75 minutes per day.
But for those who watched at least five hours of TV per day, even high levels of physical activity were not enough to eliminate higher mortality risks.
Why does TV watching for hours at a time seem to be more unhealthy than a similar amount of time sitting at a desk?
Researchers suggest that watching a lot of TV may be a marker of a more unhealthy lifestyle in general.
They also suggest that because people tend to watch TV in the evenings after dinner, it may affect their metabolism. People also tend to snack while watching TV.
Failing to meet guidelines
The study was published in The Lancet.
About 15 per cent of adults and fewer than 10 per cent of teens meet physical activity guidelines for health benefits, with some not really realising what it takes to make gains, according to Statistics Canada.
The agency compared selfreported physical activity during leisure time and objectively measured movements with a device called an accelerometer that is worn on the waist.
At the individual level, there was a discrepancy between how much some people thought they were moving and the measurements, both in terms of time spent and intensity.
“If you look at the measured data, we only have 10 per cent of teenagers that are meeting the guideline and 15 per cent of adults are meeting the guidelines, so there is room for improvement for sure,” said Didier Garriguet of Statistics Canada’s health analysis division in Ottawa.
Using self-reported data from a questionnaire, closer to between 30 and 50 per cent of people will meet the guidelines, Garriguet said.
“Maybe they’re exaggerating like overestimating what they’re doing,” he said in an interview.
The difference in terms of minutes were pretty close for teenagers. But for older adults, there was about 16 minutes less of physical activity with the measured data on average compared with self-reported data, he said. Garriguet pointed to a few possibilities to explain the discrepancy: A matter of perception of the time you’re doing an activity versus the time actually spent moving; a difference in terms of intensity, such as walking at a pace that isn’t fast enough to register, particularly for the older population.
Intensity
The differences arise since the devices and questionnaires measure different aspects of physical activity. For instance, someone could report that they played hockey for one hour but the accelerometer only records 20 minutes.
The findings come on the heels of a study published in May by researchers at York University in Toronto.
They found adults underestimate what the national guidelines for moderate to vigorous intensity physical activity are and overestimate how much they do.
Canadian physical activity guidelines, published in 2011, recommend those aged 12 to 17 get 60 minutes of moderate to vigorous intensity physical activity daily. For adults, the guidelines recommend that adults obtain 150 minutes of physical activity of that intensity per week, accumulated in bouts of 10 or more minutes.
In the York study, 129 participants aged 18 to 64 walked or jogged on a treadmill at a speed that they felt corresponded to light, moderate and vigorous intensity. Researchers asked them to judge the intensity based on how warm and out of breath they felt.
Most of the study participants were young, normal-weight women with poor cardiovascular fitness, the researchers said. More than half, 57 per cent, said they met the minimum guidelines for moderate intensity physical activity.
But they underestimated how hard they should be working to achieve moderate and vigorous intensity, the researchers found.
“In conclusion, this is the first study to determine that adults of different sexes, ethnicities and body mass index classifications underestimate moderate and vigorous intensity physical activity, and underestimate the physical activity intensity recommended for health,” Prof. Jennifer Kuk of the School of Kinesiology and Health Science at York and her co-authors said.
For those watched at least five hours of TV per day, even high levels of physical activity were not enough to eliminate higher mortality risks.