A Dire Sit-uation

You might not want to sit down for this. New research suggests that too much sitting, at work or elsewhere, may be responsible for more than just back pain and musculoskeletal complications — it could be deadly.

Add the voices of Elin Ekblom-Bak and her fellow researchers at the Swedish School of Sport and Health Sciences in Stockholm to the growing chorus of scientists who advise that too much sitting can be harmful. Ekblom-Bak’s editorial in a recent on-line issue of the British Journal of Sports Medicine cites research, including a Canadian investigation, which suggests too much time spent sitting is associated with increased risk of obesity, diabetes, cardiovascular disease and death. For those whose jobs demand eight to 10 hours of mostly uninterrupted sitting, the news may be especially worrisome.

Even more alarming is Ekblom-Bak’s view that mortality linked to prolonged sitting is “independent of moderate to vigorous-intensity physical activity.”

Peter Katzmarzyk, Ph. D., associate executive director for population science at the Pennington Biomedical Research Center (PBRC) in Baton Rouge, Louisiana, was among the researchers involved in the studies reviewed by Ekblom-Bak. Dr. Katzmarzyk concurs that those who sit for long periods are “at risk compared to somebody who sits less, regardless of the amount of exercise they do.”

In May of 2009, he and a team of researchers from PBRC and the Canadian Fitness and Lifestyle Research Institute in Ottawa released a study examining the relationship between sedentary behaviour and mortality. The investigation tracked the death rates of approximately 17,000 Canadian adults from 1981 through 1993, and found a strong association between increased time spent sitting and elevated risks of mortality from all causes — specifically, cardiovascular disease.

Noting that legs represent a large part of a person’s muscle mass, Dr. Katzmarzyk says, “When you’re sitting down, these muscles go completely inactive.” There is no EMG (electromyographic) activity, no blood flow to the area and no muscle contraction, he explains.

While researchers have yet to pin down the link between sitting and mortality, Dr. Katzmarzyk characterizes the relationship as “fairly robust.” The study sample was stratified by several different health factors, such as weight, smoking status, gender and level of physical activity, with the results remaining the same, he reports.

The findings indicate that even if accompanied by exercise and a healthy lifestyle, people who sit for long, consecutive periods are more likely to develop serious health complications.

If that’s not enough, prolonged sitting can also result in long-term damage to the back. “When a worker flexes forward in a sitting task, the spine discs bend,” says Stuart Mc-Gill, Ph. D., a professor of spine biomechanics at the University of Waterloo in Ontario. This forward flexion is the mechanism that initiates disc damage, explains Dr. McGill. “There’s not much merit [in] sitting all day,” he cautions.

Still, members of today’s work force sit more now than ever before. “The way that we work has changed a lot over the past 20 years,” says Pam Grills, an ergonomist with ErgoPrime Inc. in Ottawa. “We do a lot more computer-intensive work, which has required us to stay sitting relatively immobile for long periods of time,” Grills says.

In her editorial, Ekblom-Bak writes that sedentary behaviour should be recognized as “a distinct class of behaviour with specific determinants and effects on disease risk, separate from the behaviour of leisure-time exercise.”

Rising To Action

Fortunately, more options are becoming available to relieve workers who would otherwise be sitting all day long.

Some employers are taking action to redesign the workplace and work flow to accommodate breaks for standing. Take the City of Toronto, which employs almost 40,000 people, including phone dispatchers and administrative workers.

Alison Anderson, director of occupational health and safety for the city, says the municipality’s prevention program for musculoskeletal disorders is well-equipped to help protect sitting workers from the long-term damage. For example, work flow has been redesigned and employee training provided to allow staff to do much of their work standing. It is made clear that some standing is expected, not optional.

It may be best to embrace ways to avoid sitting while doing computer work, says Diane Stinson, an ergonomist with HealthWorks Inc. in Calgary. “There are all kinds of manufacturers now who make workstations that adjust from sitting to standing,” Stinson says.

Indeed, Anderson notes, the City of Toronto has installed a percentage of its workstations with sit-stand technology. Grills argues that 50 or 60 minutes is the most uninterrupted time that anyone should sit.

Having now demonstrated an epidemiological relationship among sitting, disease and mortality, Dr. Katzmarzyk says he and his colleagues are looking to delve even deeper and uncover some nitty-gritty details. “How long should people sit? What’s the longest duration they should sit for one time?” he asks.

Answers to those questions can help with the development of occupational physical-activity programs that will reduce sitting as much as possible, Dr. Katzmarzyk adds.

Emily Landau is editorial assistant of OHS CANADA.