SCIENCE/HEALTH
Growing evidence highlights the dangers of prolonged sitting, even for those who regularly exercise. In fact, prolonged sitting has been linked to an increase the risk of several chronic conditions, such as cardiovascular disease; obesity; type-2 diabetes; certain types of cancer; reduced circulation, which can result in blood clots including deep vein thrombosis; and reduced muscle activity, causing the muscles to weaken and increasing the risk of injury.
So, what to do? To date, few studies have compared various options to determine the minimum level of physical activity required to offset the negative health effects of sitting. However, exercise physiologists at Columbia University have just realised the findings of a comparative study and it turns out just five minutes of walking every half hour during periods of prolonged sitting can offset some of the most harmful effects of sitting.
The study, led by Keith Diaz, PhD, associate professor of behavioural medicine at the university’s Vagelos College of Physicians and Surgeons, was published in Medicine & Science in Sports & Exercise, the journal of the American College of Sports Medicine.
Unlike other studies that test one or two activity options, Diaz’s study tested five different exercise “snacks”:
one minute of walking after every 30 minutes of sitting
one minute after 60 minutes
five minutes every 30 minutes
five minutes every 60 minutes, and
no walking.
“If we hadn’t compared multiple options and varied the frequency and duration of the exercise, we would have only been able to provide people with our best guesses of the optimal routine,” Diaz says.
Each of the 11 adults who participated in the study came to Diaz’s laboratory, where they sat in an ergonomic chair for eight hours, rising only for their prescribed exercise snack of treadmill walking or a bathroom break. Researchers kept an eye on each participant to ensure they did not over- or under-exercise and periodically measured the participants’ blood pressure and blood sugar, key indicators of cardiovascular health. Participants were allowed to work on a laptop, read, and use their phones during the sessions and were provided standardised meals.
Walking for five minutes for every 30 minutes of sitting was the only option that significantly lowered both blood sugar and blood pressure. It also had a dramatic effect on how participants responded to large meals, reducing blood sugar spikes by 58% compared with sitting all day.
This option also provided modest benefits for blood sugar levels throughout the day, while walking every 60 minutes — either for one minute or five minutes — provided no benefit.
The researchers also periodically measured participants’ mood, fatigue levels, and cognitive performance. Except walking one minute every hour, all other walking options offer significant declines in fatigue and significant improvements in mood. None of the walking options influenced cognition.
“The effects on mood and fatigue are important,” Diaz says. “People tend to repeat behaviours that make them feel good and that are enjoyable.”
The researchers are currently testing 25 different doses of walking on health and testing a wider variety of people; participants in the current study were in their 40s, 50s, and 60s, and most did not have diabetes or high blood pressure.
“What we know now is that for optimal health, you need to move regularly at work, in addition to a daily exercise routine,” says Diaz. “While that may sound impractical, our findings show that even small amounts of walking spread through the workday can significantly lower your risk of heart disease and other chronic illnesses.”
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