In 1953, Jeremy Morris published a study of London’s transport workers. It revealed that drivers of double decker buses had a 42 per cent higher risk of fatal or non-fatal heart attacks when compared to bus conductors. This was despite a similar socio-economic background and age. The uniform size of the sedentary drivers was larger than that of the conductors who went up and down 500-750 steps in the bus each day. They reinforced this finding with a study which showed that sedentary telephone operators had a higher rate of heart attacks than postmen who biked and walked to deliver letters.
Subsequently, there have been many studies which showed that physical activity is good for health and longevity. However, the question remained as to whether physical activity for some periods of the day can counter the effects of prolonged sedentariness and sitting during most of the day. Emma Watson provided clarity on this in a 2012 study which pooled data from 18 studies involving 794,577 participants. She reported that an increase in sedentary time raised the risk of several adverse health outcomes: 147 per cent increase in cardiovascular disease; 112 per cent increase in diabetes; 90 per cent increase in cardiovascular deaths and a 47 per cent increase in risk of death from all causes combined. EG Wilmot also showed that these associations of increased health risks with sedentariness were mostly independent of the moderate or vigorous activity performed during parts of the day.
Sitting for long hours harmful despite short period exercises?
So, there is a need to avoid sitting for long periods of the day even if one practises the routine of exercise for short periods. Otherwise, sedentariness will cause a host of health problems: heart and blood vessel diseases (such as heart attacks, brain strokes, deep vein thrombosis and varicose veins); diabetes; obesity (general and abdominal); cancers (of colon, uterus, lung and breast); back and other joint problems; bone loss; anxiety, depression and even dementia. Sedentariness makes you a “sitting duck” for ill health.
How does sitting for long periods damage the body?
It raises blood glucose, blood fats, blood pressure, body weight and fat in the abdomen among many effects. Blood circulation also becomes sluggish, with pooling in the lower half of the body. When skeletal muscles are inactive, membranes of the muscle cells develop insulin resistance. A contracting muscle requires more sugar to provide needed energy (calories). Insulin pushes sugar into those cells from the blood. A slumbering muscle shuts the door to the entry of sugar it no longer needs, by becoming resistant to the action of insulin. That raises blood sugar, manifesting as diabetes. Blood fat levels too rise as they are no longer consumed for energy expenditure. Insulin resistance is also related to high levels of blood pressure, abdominal fat, inflammation and increased clotting tendency of the blood. Even as body weight increases, fat deposition is especially marked in the abdomen. Sitting long on the haunches is a sure bet for paunches.
Physical activity enhances muscle strength and stimulates calcium deposition in the bones. Sedentariness leads to loss of muscle and depletes bone calcium (“use it or lose it”). It also leads to slowing down of bowel movement and constipation, with the prolonged stay of toxins in the large bowel, leading to colon cancer. Inflammation damages blood vessels while sluggish blood circulation allows clots to form and grow on the injured surface. Blood fats too get deposited on areas of injury to the endothelium (inner lining) of blood vessels. The risk of heart attacks and brain strokes increases over time, due to such damage.
Sluggish flow of blood in the deep veins of the legs and pelvis leads to clots, which can get dislodged and travel to the lungs, causing the highly dangerous condition of pulmonary embolism. That is why immobility is kept to the minimum even in patients requiring bed rest, with active or passive leg exercises. The danger of deep vein thrombosis with long distance air travel is well established.
How sitting encourages unhealthy dietary practices
Prolonged sitting encourages unhealthy eating behaviours. Packaged ultra-processed foods and beverages are consumed in large quantities, initially out of boredom and later from addiction. A study of teenagers showed that those watching television were likely to gain more weight than those using a desktop computer, because the latter had their hands busy on the keyboard while the former had a remote in one hand and junk food in the other. This was true of the desktop era but the modern teenager can easily reach for chips or cola while operating a smartphone. Those used to sitting for long conveniently position food and drinks within easy reach (to snack at will or lack of will power to desist).
How ‘work from home’ legitimised prolonged sitting that weakens lungs
Even before the Covid-19 pandemic, the nature of office work or studies in schools and colleges created conditions for prolonged sitting. The pandemic brought us “work from home” and “online teaching”, where even commuting was not needed. While some employees and students did help in household work and made themselves useful as well as frequently mobile, many found the chair to be a throne they were reluctant to leave. The waves of webinars and virtual meetings also kept people tethered to their seat, with no option to move if the camera had to be kept on (unless one invoked the internet era excuse of an interrupted net connection). With prolonged sitting, even breathing becomes shallow (as the oxygen demand of muscles goes down) and many air sacs of the lung close. So, when Covid hits the lungs, there is decreased respiratory reserve. Apart from the increased risk of all other health problems associated with sedentariness, this too increases risk to life.
What should one do then?
Several solutions have been suggested, from intermittently standing and stretching to taking short walks. It is suggested this should be done frequently. That may not be possible in long flights, desultory meetings or cinema halls. However, some movement of legs and even a bit of squirming in the seat may be justified, antique etiquettes disregarded. In some offices, standing desks are being used. While that liberates and elevates the bottom, the legs still need exercise. Why not walk to a colleague to sort out a matter, instead of inflaming that person and your own arteries by shooting off terse or torrid emails from your seat? As the drillmaster at school used to order, “stand at ease”, “attention” and “quick march” is a good sequence to follow.
(Prof K. Srinath Reddy, a cardiologist and epidemiologist, is President, Public Health Foundation of India. The views expressed are personal)