A recent study from New Zealand compared the effects of prolonged sitting, prolonged standing or taking regular activity breaks on blood flow and insulin levels (PLoS One, Jan 4, 2021;16(1):e0244841) . We know from earlier studies that prolonged sitting increases risk for forming clots, but this new study suggests that people with jobs that require them to stand for long periods may be even worse off. They had higher blood insulin levels and decreased blood flow in their legs during the six hours that were measured. Decreased blood flow to the legs increases risk for forming clots, and high insulin levels are associated with increased risk for high blood sugar and diabetes. Taking regular activity breaks improved both blood flow and insulin levels.

No Benefit from Standing at Work
Some people have misinterpreted the benefits of exercise to recommend standing at work, rather than sitting, but standing at work or while watching television is not likely to do much to protect you from the increased risk for obesity, diabetes and heart attacks associated with prolonged sitting (Med Sci Sports Ex, April 2019). Standing up at work is just about the same as sitting because there is very little metabolic difference between sitting and standing. Standing increased calorie burning by less than 10 kcal/hour, which is less than 12 percent more than the calories burned while sitting. Another study of 7,300 workers found that those who stood at work were twice as likely as those who primarily sat to suffer from heart disease during a 12-year period (American Journal of Epidemiology, Jan 2018;187(1):27–33).

Factory workers, cashiers, bank tellers, teachers and others who stand several hours each day are at increased risk for psychological and muscle fatigue (Saf Health Work, Mar 8, 2012;3(1):31–42), low back pain and leg pain, blood clots in the legs, swollen legs, nocturnal leg cramps and even heart attacks (Rehabil Nurs, 2015 May-Jun; 40(3): 148–165).

Risks of Prolonged Sitting
People who sit for more than five hours a day are at increased risk for blood clots in the lungs, as are people on long airplane flights (Circulation, July 26, 2016;134:355–357). A review of 16 studies covering more than a million people, showed that prolonged sitting during working, commuting or leisure time is associated with increased risk for premature death and that this risk was eliminated completely by 60 to 75 minutes of daily moderate-to-vigorous physical activity, and was reduced by exercising just 25 minutes per day (Lancet, July 27, 2016;388:1302–10). Another review of several scientific studies also showed that prolonged sitting is associated with chronic diseases and premature death, but this increased risk was eliminated by regular exercise (Trans J of the Am Col of Sports Med, March 15, 2017;2(6):32–33; Am J Prep Med, 2011;41(2):207–15). When researchers measured the time that people spent sitting, they averaged more than 8.8 hours/day (Eur Heart J, 2015;36(39):2643–9). In another study that used accelerometers, the average sitting time was more than 7.7 hours/day (Am J Epidemiology, 2008;167:875–81), but when asked how much they sat, people under-reported their time by an average of 4.7 hours/day (J Sci Med Sport, 2014;17:371–5).

Most People Should Have an Exercise Program
The authors of the New Zealand study recommend that messages on the dangers of sedentary behaviour should “focus more on the importance of frequent movement rather than simply replacing sitting with standing.” Not exercising regularly increases risk for obesity, diabetes, heart attacks and certain cancers (Journal of Preventive Cardiology, Sep 1, 2016;23(14):1557-1564). When you sit in a chair, you fidget to make yourself more comfortable and burn a few more calories. You also fidget when you stand to relieve the fatigue and discomfort of keeping any muscle in constant contraction. People who exercise regularly fidget the most while sitting or standing, and therefore burn more calories either way. In this study, regular exercisers had lower resting heart rates, a measure of greater physical fitness.

No Standing Desks for Vigorous Exercisers
In particular, people who exercise for high levels of fitness or competition should get off their feet when they are finished with a hard workout. You recover much faster by sitting rather than standing, and lying down is even better. The faster your muscles recover, the sooner you can do your next intense workout and the more fit you will become. You delay your recovery by standing or walking when you are not exercising. Athletes and serious exercisers should ignore the ads for standing desks and sit down or lie down when they are not exercising. See Recovery: the Key to Improvement in Your Sport.

My Recommendations
Both prolonged sitting and prolonged standing at work increase risk for obesity, heart attacks and premature death. If possible, alternate standing and sitting, and take regular activity breaks (walking, stair-climbing, or any other form of movement). Whether your job requires either prolonged sitting or standing, a regular exercise program can help to protect you from clotting and other health consequences.