From The Ergoweb® Learning Center

Is It Dangerous — Even Deadly — To Sit Too Much?

An editorial in the British Journal of Sports Medicine (BJSM) has generated a lot of headlines over the past week. In a press release, BJSM states that “Prolonged bouts of sitting are a real killer, and we should focus on the harms caused by daily inactivity rather than on the lack of regular exercise alone.”

Since ergonomics is often on the front lines of any debate about sitting, ergonomists should understand the underlying theory and science behind such claims. And because this topic is making headlines around the world, expect that employees and clients will want clarification.

The editorial was written by Elin Ekblom-Bak, Mai-Lis Hellénius, and Björn Ekblom, Doctors from the Karolinska Institute and the Swedish School of Sport and Health Sciences in Stockholm, Sweden.

The authors state that the term “sedentary behaviour” has come to mean taking no exercise, but it should be more correctly used to describe “muscular inactivity."

They argue that this is an important distinction, because recent research points to prolonged bouts of sitting and lack of whole body muscular movement as being strongly associated with obesity, diabetes, heart disease, cancer, and an overall higher risk of death, irrespective of whether moderate to vigorous exercise is taken at other times.

And, they claim, the health of people who already do too little exercise will suffer even more if combined with prolonged bouts of sitting.

The authors readily admit that more research is needed to establish a causal effect between prolonged sitting and ill health, but point to some underlying mechanisms have already been identified, including an enzyme (lipoprotein lipase) that has a key role in the regulation of key blood fats. They also reference an Australian study that showed that for every additional hour a woman sits in front of the TV, her risk of metabolic syndrome – a precursor to diabetes and cardiovascular disease – increases by 26%, irrespective of how much moderate exercise she does.

The molecular and physiological responses of the body prompted by too much sitting cannot simply be cancelled out by taking additional exercise, say the authors.

Reveiwing the state of the science, the authors note:

The majority of studies conducted so far are based on self-reported sedentary time, mainly deined as  time spent watching television. This subjective method of measurement has often correctly been criticised for its limited capacity to assess sedentary time accurately. Similar independent associations of sedentary time with metabolic risk were recently obtained by the objective measurement of accelerometry. Beneficial effects of breaks in sedentary time were also reported, that is, repetitive bouts of muscular contractions interrupting muscular inactivity, compared with individuals who spent exactly the same time sitting during the day without breaks. These effects were independent of the total sedentary time.

The main point of the editorial was not to warn that everyone should stop sitting immediately, as some of the more sensationalistic headlines would have you think. Instead, the authors propose a new model or paradigm of “inactivity physiology” which recognises that sitting and non-muscular activity may independently boost the risk of ill health, and that sedentary behaviour is a distinct class of behaviour with specific consequences for ill health, which are not the same as those sparked by taking too little exercise.

The new proposed paradigm of inactivity physiology they propose is based on four tenets:

  • Sitting and limiting non-exercise activity may independently increase the disease risk.
  • Sedentary behaviour is a distinct class of behaviour with specific determinants and effects on disease risk, separate from the behaviour of leisure-time exercise.
  • The molecular and physiological responses in the human body of too much sitting are not always the same as the responses that follow a bout of additional physical exercise.
  • People already insufficiently physically active will increase their risk even further by prolonged sitting time.

“In the future, the focus in clinical practice and guidelines should not only be to promote and prescribe exercise, but also to encourage people to maintain their intermittent levels of daily activities [that involve movement],” they add. “Climbing the stairs, rather than using elevators and escalators, five minutes of break during sedentary work, or walking to the store rather than taking the car will be as important as exercise.”

Does this editorial provide enough evidence against prolonged sitting that it could quickly change the way we work? Probably not, but it is another step in a growing belief that seated work may not be the best recipe for long-term health. It also supports  recommendations that ergonomists have put forth for years — that microbreaks are better than no breaks at all, and that introducing dynamic activities (e.g., standing) is beneficial.

Many companies have already recognized improvements in productivity and quality — as well as reduced musculoskeletal disorders — by introducing sit-to-stand or dedicated standing workstations. If the authors of this editorial are correct when they link prolonged sitting to a host of diseases and disorders, we can expect to see more people and companies recognizing benefits from standing work.

This article originally appeared in The Ergonomics Report™ on 2010-01-25.