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How much exercise do we need to offset the negative effects of prolonged sitting? A new study offers clues. Elena Kharichkina/Stocksy
  • Around 22 minutes of moderate to vigorous physical activity a day can eliminate the increased risk of death associated with a sedentary lifestyle, a new study indicates.
  • The more people exercise, the greater their mortality risk decreases.
  • The study findings show that daily exercise can be carried out all at once or in exercise “snacks” throughout the day.

A new study suggests that a person can reduce their mortality risk with much less exercise than one might think.

The study finds that just 22 minutes of daily moderate to vigorous physical activity (MVPA) can reduce one’s risk of dying prematurely as a result of a sedentary lifestyle.

The beneficial effects of exercise are, of course, dose-dependent, so the more exercise, the greater a reduction in mortality risk, up to a point.

The study’s authors tracked 11,989 people who participated in several fitness-tracker-based studies: the Norwegian Tromso Study, the Swedish Healthy Aging Initiative, the Norwegian National Physical Activity Survey, and the U.S. National Health and Nutrition Examination Survey.

All the people in the studies were at least 50 years old and reported to researchers their weight, height, sex, educational level, alcohol use, smoking, and any incidence of previous cancer, cardiovascular disease, or diabetes.

Of the participants, 5,943 individuals were sitting for less than 10.5 hours every day, while 6,042 individuals sat for 10.5 or more hours daily. The researchers aimed to assess the effect of sedentary time and physical activity on mortality risk, as derived from death registries.

For people exercising less than 22 minutes a day, sitting for more than 12 hours was associated with a 38% increased risk of death compared to sitting for 8 hours.

The World Health Organization (WHO) recommends 150–300 minutes of moderate-to-vigorous exercise per week or at least 75 minutes of vigorous exercise, or a combination of both.

The study was published in the British Journal of Sports Medicine.

The study’s first author, Dr. Edvard H. Sagelv, from UiT The Arctic University of Norway in Tromso, said: “The research field is a little bit divided on how sedentary time is dangerous. I would say, compared with not doing physical activity, sedentary time is not that dangerous.”

“However, previous research indicates that excess sedentary time is increasing the risks of disease and premature death,” he added.

Dr. Tracy L. Zaslow, a primary care sports medicine physician practicing in Los Angeles, California, who was not involved in the study, explained, “To put it simply, when we’re sedentary, we use our muscles less, and it’s use it or lose it.”

“If we’re not using our legs and our core muscles, they’re going to become weaker, and then we’re less likely to want to be active because it’s harder to walk a little further,” she added.

This also increases the risk of falling, at which point we may acquire injuries that make us even more reluctant to be physically active.

“Remember, the heart is a muscle,” cautioned Dr. Zaslow.

She noted that the less we engage in activity, the weaker the heart muscle becomes, so physical activity becomes even more challenging because it becomes necessary to recondition the heart. Being sedentary has been associated with cardiometabolic disease, said Dr. Zaslow.

While the study focuses on older people, said Dr. Melody Ding, also not involved in the study, “Physical activity is known to offer a range of benefits, such as mental health, cardiometabolic profiles, and cognitive functions.”

“There are good reasons to be active across the lifespan,” said Dr. Ding.

Dr. Zaslow pointed out that even children need to build and strengthen muscles by exercising and that doing so sets them up for a lifetime of physical activity.

In addition, mental health, including a reduction in anxiety and depression, is associated with being active. Given the widely reported mental health crisis among young people, said Dr. Zaslow, this is yet another important benefit.

Exercise also promotes better sleep, she suggested, facilitating falling asleep more quickly and achieving deeper sleep. “We know that when we sleep better, we have fewer injuries. So, by sleeping more than eight hours, studies have shown that kids have 50% less injuries.”

“I kind of look at exercise and having the regularity of exercise as being like an upward spiral,” Dr. Zaslow said.

Dr. Sagelv pointed out that the study’s 22 minutes of physical activity a day adds up to the 150 minutes prescribed by the WHO.

“Our study found that Individuals doing more than 22 minutes of moderate-to-vigorous physical activity per day had no increased risk of death with more sedentary time. This contradicts the WHO recommendation to exceed 150-300 minutes of MVPA per week when dealing with unavoidable high sedentary time,” he said.

As to exceeding 22 minutes a day, Dr. Sagelv noted:

“That is a beautiful part. There appears to be no upper limit at which it does not provide any health benefits. However, at the higher ends, about 60-120 min per day, the risk reduction appears to level off a bit, especially for those being highly sedentary.”

People do not need to complete 22 minutes of activity all at once each day, either, according to Dr. Zaslow and previous research. “Exercise snacking” involves taking 10 minutes here and 15 minutes there, and may be easier for some to integrate into their busy lives.

“From the public health [perspective], it is important to remember that doing any MVPA is better than doing none. Even if one cannot achieve the target, it is better to do a little more,” said Dr. Ding.