Movement and sitting: it's all about your health, By Jenny Pynt PhD

Dr. Jenny Pynt is an internationally recognized expert in the field of sitting ergonomics.  She has written four books, and numerous research and lay articles on healthy sitting, chair design, and lower back pain.  You may see Dr. Pynt's resume here. 

Since the 1970’s health professionals have been researching and advocating the importance of movement while seated. The focus of this research has been the health of the spine. In particular the impact that movement or the lack of movement has on the discs, ligaments, joints and muscles of the spine when seated. In the last decade research has also shown that those who sit or stand statically for long periods of the day are at risk of metabolic and long term systemic health consequences. And if you consider that Mayo Clinic researchers state that “1 in 4 white US adults spend about 70% of their waking hours sitting”,1 then many people are at increased risk of type 2 diabetes, cardiovascular diseases, colon cancer, postmenopausal breast cancer from sitting. Inactivity is also thought to play a role in the development of dementia and depression.2

These systemic ill effects are driven by lack of muscle contraction. In the short term the decreased muscle contraction that occurs with prolonged, immobile sitting slows the clearance of fat from the blood stream and decreases the effect of insulin. In the long term these effects cause obesity, heart disease, type 2 diabetes and some forms of cancer.3

But just because your job involves a lot of sitting you do not have to succumb to this cascade of events. One of the ways to address this problem is to introduce as much movement as possible into your day. Even light activity requiring low energy expenditure is important. Such activities are known as NEAT (non exercise activity thermogenesis). This acronym was devised by DrJames Levine of the Mayo Clinic, to describe the thousands of small movements you make inyour daily office routine e.g. getting up to go to the water cooler, or the toilet, doing pause exercises. Even fidgeting. These sporadic movements break the pattern of sustained inertia, and in a day increase the total energy expended.4

Expending energy uses calories. Owen and colleagues recently found that every minute of sedentary behaviour replaced by light activity, such as standing and incidental walking, uses 1 additional kilocalorie. Hamilton and co-workers noted that “supporting the mass of the body in combination with spontaneous movement or very slow ambulation (1 mph) raises whole-body energy expenditure 2.5-fold more than when seated still.”5  These researchers also found that chair bound workers who move infrequently used as little as 300 kilocalories a day in activity.  And workers who remained seated for 2 hours/day longer than their colleagues, were also fatter than their colleagues. Artinian and co-workers discovered that even modest sustained lifestyle changes (such as adding more activity to your working day by walking to a colleague’s office rather than emailing, climbing stairs rather than catching lifts, walking up escalators) accrue over time and can substantially reduce cardiovascular disease.6 So it stands to reason that increasing incidental movement in your day will use more calories and help to break the adverse impact that sustained sitting has on general health.

Increasing incidental activity at the desk by using a standing desk

One method of increasing incidental activity currently very popular with the media is that you stand to work at your computer. Standing uses more muscle work than sitting, thus contributing to increased energy expenditure. However, the health benefits of standing to work require qualification if you are to avoid painful ramifications. The most important qualification is that to avoid postural pain you must move while standing, just as you must move when sitting. The following ramifications of standing stationary at your desk are frequently omitted in the “Standing versus Sitting” debate:

Stationary  standing can cause back pain

• Occupations that require standing for periods of more than 30 minutes in the hour show high incidence of back pain.⁷
• Although more women work from fixed standing postures than men, low back pain occurs in either sex if people work from a fixed standing position.⁸
• People who have the freedom to sit when they wish, have less low back pain than those who stand in fixed postures.⁹
• Standing stationary causes constant loading through the same joints and tissues in the spine and lower limbs and little provision for rest or change in levels of muscular activity.

Stationary  standing can cause circulatory insufficiency in the legs

• Prolonged standing causes pooling of the blood in the legs with sluggish return of blood to the heart, swelling of the legs and the possibility of blood clot in both men and women.  In females prolonged standing can cause preterm birth and spontaneous abortion.¹⁰
• People with occupations requiring prolonged standing have increased incidence of varicose veins and nocturnal cramps.¹¹
• People working in a fixed standing posture are at a significantly greater risk of cardiovascular disease than those working in a fixed sitting posture.¹²

In short simply standing to work, but forgetting to move, is no more helpful to health than stationary sitting.

The effect of movement on spinal health

Movement has the potential to counteract many health issues that occur in the spinal discs, joints, muscles and ligaments from stationary sitting. It is most effective when muscles are used to promote the movement. For example moving the low back actively from slump to erect 6 times every 15 minutes, turning the neck maximally to either side/up and down/side to side, moving the legs whenever possible.

The effect of movement on the discs

The discs are the cushions between the vertebrae. They are filled with fluid and act as shock absorbers for the spine. Movement of the spine causes an exchange of fluid in the disc, bringing fresh fluid with nutrition into the disc and pumping waste out (the discs, unlike the muscles, do not have a blood supply to perform this task). If however you sit without moving, the fluid in the discs leaks out, but no fresh fluid is brought in. The disc spaces narrow, the protective cushioning from the discs is lost, the ligaments lose their tension and the joints on either side of the spine (the facet joints) are compressed. Sitting slouched without movement for periods as short as 5 minutes has been demonstrated to result in an unprotected and unstable spine primed for injury.¹³(For this reason whenever you’re not moving, for most people it is important to sit in postures that maintain some degree of the natural curve of your low back.)

The effect of movement on the spinal joints

If the joints become narrowed from lack of movement then the nerves that supply sensation to the legs can be compressed causing pain. If you sit stationary for prolonged periods with the back fully arched you will also experience pain from compression of the joint surfaces. The best way to avoid compression either of nerve or joint surfaces is to move. Movement also spreads the load of the trunk between the discs, joints, ligaments and muscles of the spine, easing the burden from one structure alone.

The effect of movement on the spinal ligaments and muscles

The ligaments require movement to remain elastic. Normally when the spinal ligaments become stretched a reflex fires that contracts the spinal muscles to protect the spine. However, if you sit stationary in a slouched posture for greater than 10 minutes, the ligaments in the spine become overstretched, fluid is forced out and bathes the ligament and muscles, the stretch reflex is inhibited and the muscles cannot fulfil their protective role. The discharged fluid acts as an inflammatory agent causing the muscles to spasm intermittently. In the short term the spine is vulnerable to injury because its protective mechanism is asleep. In the long term the stage is set for a cumulative trauma disorder because the outpouring of irritating fluid causes inflammation.¹⁴The result in both the short and long term is pain.

Summary

Moving while sitting is essential to health. Incidental activity improves body metabolism and has been shown to impact positively on heart function, diabetes and waist measurement. The spinal joints and discs also benefit from the movement because the load on them is alternated, waste products are removed, and nutrition is improved. Alternating movements between muscle groups is essential to avoid fatigue in one set of muscles with resultant pain.

When choosing a chair a priority is a design that encourages movement.
A high priority is one that also encourages you to actively exercise.

Copyright of this article remains with the author Dr Jenny Pynt

References

¹ Owen, N. et al. (2010) “Sedentary Behavior: Emerging Evidence for a New Health Risk” Mayo Clin Proc.85 (12):1138-1141, p.1139

² Pedersen BK (2009) “The diseasome of physical inactivity” J Physiol 587.pt 23 pp 5559–5568

³ Katzmarzyk PT. et al (2009) “Sitting time and mortality from all causes, cardiovascular disease, and cancer.” Med Science Sports Exercise 41(5):998-1005.

⁴ Levine, J. A. et al. (2006). “Non-exercise activity thermogenesis: the crouching tiger hidden dragon of societal weight gain.” Arteriosclerosis, Thrombosis, and Vascular Biology 26: 729-736.

⁵Hamilton, MT. et al. (2007) “Role of Low Energy Expenditure and Sitting in Obesity, Metabolic Syndrome, Type 2 Diabetes, and Cardiovascular Disease”. Diabetes 56:2655–2667, p. 2660.

⁶ Artinian N. et al. (2010) “Interventions to Promote Physical Activity and Dietary Lifestyle Changes for

cardiovascular Risk Factor Reduction in Adults: A Scientific Statement From the American Heart Association”, Circulation, 122:406-441.

⁷ Andersen JH. et al. (2007) “Risk Factors for More Severe Regional Musculoskeletal Symptoms. A Two-Year Prospective Study of a General Working Population.” Arthritis and Rheumatism, 56(4): 1355–1364.

⁸ However more men work in stationary sitting positions than women. Tissot F. et al. (2009) “Studying the

relationship between low back pain and working postures among those who stand and those who sit most of the working day”. Ergonomics, 52(11):1402-18.

⁹ Tissot p.1402.

¹⁰McCulloch J. (2002) “Health risks associated with prolonged standing.” Work; 19(2):201-5; Shai A. Et al. (2007)

¹¹Bahk JW. et al. (2011) “Relationship between prolonged standing and symptoms of varicose veins and nocturnal leg cramps among women and men.” Ergonomics, 55 (2) 133-139.

¹² Sudol-Szopinska I. et al. (2011) “Prevalence of chronic venous disorders among employees working in prolonged sitting and standing postures.” Int J Occup Saf Ergon, 17(2):165-73.

¹³Andersson, BJG. et al. (1975) The sitting posture: An electromyographic and discometric study. Orthop. Clin. Nth. Am. 6, 105-119.

Dolan, K., Green, A. (2006) “Lumbar spine reposition sense: the effect of a 'slouched' posture”. Man. Ther. 11, 202-207.

¹⁴ Solomonow, M. (2006) “Sensory-motor control of ligaments and associated neuromuscular disorders”. J. Electromyogr. Kinesiol.. 16, 49-67.

Solomonow, M. (2009) Ligaments: A source of musculoskeletal disorders. J. Bodyw. Mov. Ther. 13, 136–154.