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Sitting is something that most people do well every day, whether at the office, on public transport or at home.
But because of vascular dysfunction, sitting in one place for a long time can increase the risk of serious health problems like cardiovascular disease and type 2 diabetes.
In 1953, epidemiologist Jeremy Morris discovered that London bus drivers were more likely to encounter bus conductors and develop heart disease.
Demographically (age, gender and income bracket) the two groups of workers are identical, so why do we say we get this significant difference?
Morris responds: Bus drivers’ jobs require them to stand and regularly climb the steps of London’s iconic double-decker buses to sell tickets to passengers, while conductors sit for long periods.
This study served as the basis for research into the links between physical activity and coronary health.
Even though London bus drivers don’t rule the roost like they used to, Morris’s findings are more relevant than ever.
Since the Covid-19 pandemic, we are seeing a huge shift towards working from home, which is likely to increase our collective sitting time.
Without our usual need to grab water from the cooler and move from meeting room to meeting room, it’s easy for people to spend hours sitting at their desks without getting up.
(Office culture, however, has already changed our working lives since the 1980s, so much so that some researchers have joked that our species has become Homo sedens – meaning “sitting man” – rather than Homo sapiens.)
Prolonged sitting is a form of sedentary behavior, characterized by very low energy expenditure while sitting or lying down.
Typical sedentary behaviors including watching television, playing games, driving, and working at a desk.
Sedentary behaviours are associated with a higher risk of cardiovascular disease, type 2 diabetes and premature mortality, and the time we spend sitting in particular has been identified as an independent risk factor in a range of health problems.
In 2020, the World Health Organization suggested measures to reduce sedentary behavior.
Sitting for long periods of time is a form of sedentary behavior, said to signal very low energy expenditure while sitting or lying down.
Typical sedentary behaviors include watching television, playing games, driving, and working at a desk.
Sedentary behaviours are associated with a higher risk of cardiovascular disease, type 2 diabetes and premature mortality, and the time we spend sitting in particular can be identified as an independent risk factor for a range of health problems.
For 2020, the World Health Organization suggests measures to reduce sedentary behavior.
Since 2010, researchers have been pointing out that a sedentary lifestyle is synonymous with a lack of physical activity. You exercise every day and yet you sit too long.
However, the risks associated with sedentary behavior are greater for those who do not get enough exercise.
Does sitting for long periods of time increase the risk of cardiovascular disease?
Where does this photo come from, Getty Images
In fact, sitting for long periods of time increases vascular dysfunction, especially in the legs.
According to Sabi Pipo, the vascular system is responsible for keeping blood and lymph fluid – part of the immune system – moving through the blood vessels.
David Dunstan, a physiologist at the Institute of Physical Activity and Nutrition at Deakin University in Melbourne, Australia, has conducted extensive research into the effects of prolonged sitting and possible interventions.
“The main problem with sitting is reduced muscle activity,” Dunstan said. “If I sit in a chair, the chair takes all the blame.”
The combined effect of reduced muscle activity, lower metabolic demand and gravitational forces decreases blood flow to the leg muscles, leading to blood pooling in the calves.
The biomechanics of sitting, with the legs typically bent, also reduces blood flow.
Researchers suggest that anyone who sits for 120 to 180 minutes in one place is not healthy.
Reduced muscle activity in the leg muscles reduces metabolic demand. Metabolic demand is the primary determinant of blood flow, so blood flow to the legs is also reduced. The biomechanics of sitting, where people have to bend their legs, causes blood to pool in the calves – a study of 21 healthy young volunteers showed that calf circumference increased by almost 1 cm (0.4 in) over two hours. This also reduces blood flow.
Normal blood flow causes friction, called arterial shear stress, against the endothelial cells that line the walls of blood vessels. The endothelium responds to this force and secretes vasodilators, such as adenosine, prostacyclin, and nitric oxide, which keep the vessels adequately dilated and preserve the ability of the vascular system to self-regulate, what many call homeostasis.
However, reduced blood flow reduces shear stress and the endothelium produces vasoconstrictors such as endothelin-1 which causes the blood vessels to narrow. In a vicious cycle, vasoconstriction further reduces blood flow and blood pressure increases to keep the blood moving. High blood pressure is one of the major risk factors for cardiovascular disease.
“Dat [vascular dysfunction] “This is one potential mechanism,” Dunstan adds. “But the truth is that we have never been able to identify the exact mechanisms, and it is also possible that there are multiple mechanisms.
Although the underlying mechanisms are speculative, recent studies support this theory. One study of 16 healthy young men found that sitting for three hours increased blood pooling in the legs, peripheral vascular resistance, diastolic blood pressure, and leg circumference. Another study found that blood pressure increased with the amount of time spent sitting uninterrupted. Researchers generally agree that 120 to 180 minutes of uninterrupted sitting is probably the threshold that indicates you’re probably not sitting too much, but vascular dysfunction generally increases with the amount of time people spend sitting.
Sitting for a long time after cutting is harmful
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Sitting for a long time after eating a high-fat meal is harmful.
The musculoskeletal system is also likely to be affected. Sitting for a long period of time contributes to reduced muscle strength, decreased bone density, and increased total and visceral fat in adipose tissue.
Additionally, prolonged sitting is associated with physical discomfort, work stress and increased depression, which can even lead to pressure sores.
Dunstan, who also specializes in type 2 diabetes research, also says that increased sedentary behavior after meals, or after meals, increases blood sugar and insulin. Impaired insulin sensitivity and impaired vascular function both contribute to a higher risk of cardiovascular disease and type 2 diabetes.
People are becoming more sedentary because society encourages them to be. As it becomes more efficient, we don’t need to move around as much – Benjamin Gardner
With all these well-known potential consequences, why are we said to sit for so long – and how can we break the habit?
“I feel like people are becoming more sedentary because that’s what society encourages,” he added.
Benjamin Gardner, a social psychologist specialising in all habitual behaviours at the University of Surrey who has studied why people sit for so long, says: “You can’t say that someone is deliberately pushing them. You just say it’s more efficient now, you don’t have to move around as much.”
For 2018, Gardner and colleagues found that ways to encourage people to get up to attend meetings could pose unique social barriers.
“We encourage pipo to try this [standing up] “For three different meetings, and we surveyed them after each meeting to see how they were doing, and the results shocked us,” Gardner said. “For a formal meeting, these people feel like he’s the sandman.”
Wetin Fit helps your body
Getting up often to take a short walk or climb a few stairs is also beneficial.
Wearable technology can also help remind us to move. Wearable devices called accelerometers will provide 24-hour data on individual behavioral patterns, including sitting, standing, sleeping and exercising, according to a promising new study.
As Dunstan Bin pointed out earlier, this will potentially help optimise sitting and standing times, with the devices sending automatic reminders whenever you’re sitting for too long.
However, using technology is not without its drawbacks, as some people may become frustrated by the difficulty or inability to send messages.
Above all, Gardner and his colleagues encourage moving from sitting to standing more frequently.
The principle of breaking up sedentary time by simply getting up is simple, but it provides significant health benefits, especially for people who are not very active.
For people in wheelchairs or with disabilities who have mobility constraints, specific and adapted exercises can help them.
For many, it’s hard to avoid a sedentary lifestyle in the name of modern life and work. But even small changes to your routine – stretching more, moving around or getting up to make a cup of tea – can help you break the sitting habit.