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Providing perspectives on recent research into vitamins and nutritionals


Coaching the Couch Potato Off the Sofa and Office Chair

By Julia Bird

A few years ago, a number of influential studies were published that linked a greater amount of time spent sitting with an increased mortality risk. For example, Bjørk Petersen and colleagues found a doubled risk of mortality when people sitting less than 6 hours per day were compared to those sitting more than 10 hours per day in a large group of Danish adults. Pavey and co-workers also found that elderly Australian women who sat for more than 11 hours per day had a 1.5 times higher risk of death compared to women sitting less than 4 hours. And a meta-analysis from Wilmot and associates found that risk of mortality increased by 50% when comparing the most sedentary with the most active sectors of the population. Reducing sitting time may therefore reduce early deaths.

However, many of us spend a great deal of our lives sitting. Matthews et al. found that the average US adult spends almost 8 hours per day sitting, around 55% of waking hours. This is due to our jobs, which increasingly are sedentary, and the popularity of leisure activities such as watching television or using the computer. As we are unlikely to see sitting times decreasing for the majority of workers’ jobs, and television remains popular even while we increase time spent in other sedentary leisure activities (see reports from the US and UK), what could stimulate us to move more and sit less?

A news report from the Centers for Disease Control and Prevention discusses the results of an intervention aimed to reduce office workers’ sitting time. 60 office workers at a large university were assigned a special wrist monitor that gave hourly prompts: half were encouraged to stand, and the other half were encouraged to stand at walk at least 100 steps. The wrist monitors also measured physical activity, including whether the workers were sitting or standing. The intervention was carried out over three work days on two consecutive weeks: the first week was used to establish baseline activity levels, and the intervention took place during the second week.

Could this simple intervention affect sitting time? At baseline, these workers were spending 6.3 hours at work sitting, 1.3 hours per day standing, and 39 minutes walking. They also stood up around 29 times per day. Overall, the simple prompts reduced sitting time by 5 percent, equal to 18 minutes per day. This was significant only for the group receiving instructions to stand only, and there was no clear difference for workers instructed to stand and walk. Even so, the average amount of time spent walking increased by 23% for the people asked to stand only, and 29% in the people asked to stand and walk. This second group also increased the number of steps that they took each day.

It seems that it is possible to encourage people to modestly shift their sedentary behavior towards greater amounts of activity. While this intervention was very short term, it gives hope that it is possible to encourage people to move more. Further interventions aimed at increasing activity levels, tested for longer periods of time and measuring health-related endpoints are needed. Perhaps the next step is to see whether the pedal-powered laptop will gain traction as employers seek to improve their workers’ fitness?

Main citation:

Centers for Disease Control and Prevention. Hourly Prompts Reduce Workers’ Time Spent Sitting. JAMA. 2014;311(22):2265. doi:10.1001/jama.2014.5841.

Supporting citations:

Bjørk Petersen C, Bauman A, Grønbæk M, Wulff Helge J, Thygesen LC, Tolstrup JS. Total sitting time and risk of myocardial infarction, coronary heart disease and all-cause mortality in a prospective cohort of Danish adults. Int J Behav Nutr Phys Act. 2014 Feb 5;11:13. doi: 10.1186/1479-5868-11-13

Charles E. Matthews, Kong Y. Chen, Patty S. Freedson, Maciej S. Buchowski, Bettina M. Beech, Russell R. Pate, and Richard P. Troiano. Amount of Time Spent in Sedentary Behaviors in the United States, 2003–2004. Am. J. Epidemiol. (2008) 167 (7): 875-881 first published online February 25, 2008 doi:10.1093/aje/kwm390

Pavey TG, Peeters GG, Brown WJ. Sitting-time and 9-year all-cause mortality in older women. Br J Sports Med. 2012 Dec 15. [Epub ahead of print]

Wilmot EG, Edwardson CL, Achana FA, Davies MJ, Gorely T, Gray LJ, Khunti K, Yates T, Biddle SJ. Sedentary time in adults and the association with diabetes, cardiovascular disease and death: systematic review and meta-analysis. Diabetologia. 2012 Nov;55(11):2895-905. doi: 10.1007/s00125-012-2677-z. Epub 2012 Aug 14.