Countering the Harm Done by Prolonged Sitting
By Ragnar Viir, MD, PhD
- WHO/The Ottawa Charter for Health Promotion, 1986
Technological developments have brought about an astonishingly swift change in human behaviour on a global scale. We evolved over thousands of years to be hunter-gatherers, bipedal, frequently on the move. The advent of mechanised transport, TV, and most notably the PC, has, within a few decades, turned us into machine-dependent sedentary creatures.
What is wrong with that?
The problem is fundamentally a physiological one. Over three hundred years ago Ramazzini recognised that the prolonged sitting required of clerks resulted in specific health disorders. Sadly this insight was lost. During the London Blitz in 1940 the number of deaths from thromboembolisms in elderly females sitting for long hours in air raid shelters was significantly reduced by the introduction of bunk beds. In 2004 a twenty-year old Korean was reported of dying of a thromboembolism after eighty hours continuously sitting at a computer display station. Chair dependency is also linked to cardiovascular disease, metabolic sequelae, excess weight, and even a shorter life span. The evidence is rapidly accumulating. Indeed Seated Immobility has become a global health challenge.
There are many proposed solutions to chair-associated ill health ranging from population-wide promoting of optimal physical activity (Patel et al., 2010) through pharmacological administration (Sleight et al., 2006) even to genetic manipulation (Franks, 2010) as referred to by Levine in his paper “Health-chair reform: Your Chair: Comfortable but Deadly” (Levine, 2010). However a fact that is in danger of being overlooked is that the relationship between seated immobility and health problems is primarily one of the duration of the sitting time itself. One of the sobering findings has been that exercising in leisure time does not counteract the effects of constant sitting (Owen at al., 2009, Bak et al., 2010). Indeed human and animal studies suggest that frequent episodes of low-intensity meandering-style activity may benefit health more than occasional bouts at the gym (Bey and Hamilton 2003, Patel et al., 2010).
Why could that be so?
The essential, complex role of muscles in physiological health is gradually becoming clearer, in part as new technology enables us to make more sensitive measurements.
A healthy musculo-skeletal system underpins all aspects of physical wellbeing. Every living muscle exhibits some tension. Anatomically speaking without tension the body cannot be integrated. Tension in muscles inevitably has to be involved in holding the seated posture, as stated by Borelli way back in 1685.
To investigate this, we measure the passive tension of a muscle, which is a combination of its inherent viscoelastic property and its neurally activated low-level contraction – “summary tension” in short.
Previously, electromyography (EMG) has been the preferred instrument for such investigations. However, it could only detect the neurally controlled part of the summary tension. In a recent day-long EMG muscle monitoring study (by Finni et al., 2010) the results arrived at were interpreted as showing that our muscles are in a resting state for most of the waking period, namely over 70% of the daytime.
However, for my thesis work (Viir, 2010) I used newer technology, the Myoton® developed at the University of Tartu (Vain, 2000) and concentrated on the tibialis anterior, the upper trapezius, and the forearm extensor muscles in different circumstances – both in weightlessness simulation mode, using water immersion, as used in gravitational physiology studies, and under gravitation. I measured the tension when standing, sitting, and lying down. I have been able to demonstrate that there is an up to 20% decrease in passive summary tension in the upper trapezius, as registered in Hertz, when lying down, as compared with when standing or sitting. This effect was enhanced in the immersion model, thereby uncovering the effect of gravity on muscle.
Thus, for the first time it has been clearly demonstrated that there is a measurable tension in passive skeletal muscle in all positions under gravity, that this varies with the bodily position, and that now one can adequately characterise the sitting position. This should provide the scientific basis for the evaluation of a variety of skeletomuscular conditions and their treatment.
Further, my study reveals that there is a significantly higher tension when sitting than when lying. This is a new, scientifically based, observation in the field of muscle biomechanics and sedentary life studies. Therefore we must be aware not only of the need for muscles to recover from physical exercise, but also of the need for muscles to recover from long periods of passive muscular tension, such as is incurred in lengthy periods of sitting.
And the reason for this is quite serious.
The muscular system with its motor activity is the important environment for normal metabolic and immune processes. Gravitational physiology uses the phrase “Second Heart” to describe the role skeletal muscle plays in assisting the cardiovascular system. But constantly tense muscle cannot be effective as a second heart, and may lead to the cascade of ill effects now being called “the Sitting Disease”.
For instance, it has long been known that flexing the feet while lying down more than doubles the lymph flow, as compared with when exercising in an upright position (Olszewski and Engeset, 1980). I posit that simple movements performed lying on one’s back result in enhanced effects, with respect to micro and macro circulation, compared to those done in a semi-upright or upright position. And I predict that muscle blood flow measurements will ultimately prove this.
Further research is urgently needed to successfully counter the plague of ill effects caused by seated immobility, both in the workplace and in everyday life. Meanwhile, in my experience, the following strategy has been very effective in affording quick relief from over-tensed muscles in computer keyboard operators.
In each seated hour two minutes should regularly be taken to lie down on one’s back, make brisk walking-style movements, alternating these with relaxed circular movements of the arms and shoulders. This very simple exercise to reduce tension should also appeal to employers because of its ease of implementation and cheapness. All that is needed is a mat per ten people and a roster to provide quick, effective recovery from excessive sitting, which otherwise will lead to neck and shoulder pain in the workplace (please see in You Tube: http://www.youtube.com/watch?v=oJvwdn1XJ4s ).
Above all, keep moving.
I wish to thank Mrs. Eva-Kersti Holmes for her careful revision of the English in this paper – RV.
Franco G. Ramazzini and worker’s health. Lancet 1999;354:856-861.
Simpson K. Shelter deaths from pulmonary embolism. Lancet 1940;i:744.
Lee H. A new case of
fatal pulmonary thromboembolism associated with prolonged sitting at computer
Patel AV, Bernstein L, Deka A, Feigelson HS, Campbell PT, Gapstur SM. Leisure time spent sitting in relation to total mortality in a prospective cohort of US adults. Am J Epidemiol 2010;172:419–429.
Sleight P, Pouleur H, Zannad F. Benefits, challenges, and registerability of the polypill. Eur Heart J 2006;27:1651–1656.
Franks PW. Diabetes family history: a metabolic storm you should not sit out. Diabetes 2010;59:2732–2734.
Levine JA. Health-chair reform: your chair: comfortable but deadly. Diabetes 2010;11:2715-6.
Owen N, Bauman A, Brown W. Too much sitting: a novel and important predictor of chronic disease risk? Br J Sports Med 2009;43:81–83.
Bak EE, Hellénius ML, Ekblom B. Are we facing a new paradigm of inactivity physiology? Br J Sports Med 2010;44:834-835.
Bey L, Hamilton MT. Suppression of skeletal muscle lipoprotein lipase activity during physical inactivity: a molecular reason to maintain daily low-intensity activity. J Physiol 2003;551(pt 2):673-682.
Finni T, Haakana P,
Tikkanen O, Petrin M, Pullinen T. Physical activity and inactivity during
normal daily life quantified by using electromyography. Proceedings of 13th
World Sport for All Congress 14-17 June 2010
Viir R. The Effect of Different Body Positions and of Water Immersion on the Mechanical Characteristics of Passive Skeletal Muscle. Doctoral Thesis 2010. ISSN 1406–1058, ISBN 978–9949–19–460–5 (Print), ISBN 978–9949–19–461–2 (PDF).
A. A Method and
Device for Recording Mechanical Oscillations in Soft Biological Tissues, 2000
Olszewski WL, Engeset A. Intrinsic contractility of prenodal lymph vessels and lymph flow in human leg. Am J Physiol 1980;239:H775–783.
Ragnar Viir is a Medical Doctor specializing in physical medicine and rehabilitation (PM&R); he recently completed his PhD in Exercise and Sport Sciences (Kinesiology and Biomechanics). This paper is based upon Dr. Viir’s doctoral thesis.
[ BWW Society Home Page ]
© 2011 The Bibliotheque: World Wide Society