Research Review By Dr. Shawn Thistle©

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Date Posted:

September 2011

Review Title:

Occupational Sitting: Research Updates

Studies Included:

  1. Ryan CG, Grant PM, Dall PM & Granat MH. Sitting patterns at work: Objective measurement of adherence to current recommendations. Ergonomics 2011; 54(6): 531-538.
  2. O’Sullivan K et al. Neutral lumbar spine sitting postures in pain-free subjects. Manual Therapy 2010; 15: 557-561.
  3. Horton SJ, Johnson GM & Skinner MA. Changes in head and neck posture using an office chair with and without a lumbar support. Spine 2010; 35(12): E542-E548.

Background Information:

Modern day occupations often require periods of long, uninterrupted sitting. Although many of our patients have trouble making a connection between this pattern and their general health, those of us in clinical practice know this can be a recipe for disaster. Put simply, our society sits still way too much, and it seems that this pattern will only worsen over time. Not only do too many people sit still all day at work, they then have to sit in the car during their commute, then they get home and…you guessed it, they sit and eat, watch TV, play video games or surf the internet, and so on. Sitting, particularly slump sitting, can promote increased thoracic kyphosis, forward head posture, posterior pelvic tilt and loss of lumbar lordosis, and so on (see diagram below). Although there is evidence that occupational sitting is not an independent risk factor for LBP (1), the potential contribution to this syndrome remains reasonable and it has been shown to be an aggravating factor in those with LBP (2). From a general health perspective, this ‘occupational and lifestyle stressor’ may be more damaging to our society’s health than we currently acknowledge. In fact, emerging evidence suggests that sedentary behavior is a risk factor for many health conditions, independent of physical activity level (3) (NOTE: you read that correctly, there seem to be deleterious health effects from sitting even if someone exercises!).
Cogwheel Sitting
Patients with sedentary office jobs flood our offices with all sorts of postural, spinal and even peripheral syndromes that we often attribute, at least in part, to their occupation. This is something that most of us discuss with many of our patients but as a clinician I have always wondered: How can the literature help us help our patients with this? What are the key concepts and easiest strategies to implement to combat the stress that numerous hours of sitting place on our patients? This is a huge topic to be sure and would require numerous reviews to cover in thorough detail. Having said that, I thought the information in these three papers could help us get a glimpse into some areas of research on this topic that translate easily into some practical advice we can provide for patients.

Pertinent Results:

Occupational Sitting Guidelines and Current Patterns:
  • Although it is commonly accepted that prolonged sitting has deleterious health effects, there is a paucity of real-life, occupational data on the actual daily habits of workers. In addition, there is no gold standard guideline on acceptable levels of sitting that incorporates biomechanical, productivity and patient-centered variables. There is also much debate on what constitutes ‘ideal’ sitting posture.
  • Ryan and colleagues (#1 above) conducted an observational, real-life study of sitting patterns in a group of 83 office workers and compared their data to existing guidelines on sedentary behavior. Using a body-worn accelerometer (activPAL™), data was collected over a period of five working days. The authors then compared this data to the current recommendations that do exist regarding safe levels of sitting. These three recommendations, each specifying maximum sitting time, come from different sources:
    1. Maximum sitting time of 20 minutes per session (Chartered Society of Physiotherapy, 2005) (4)
    2. Maximum sitting time of 30 minutes (Atlas & Deyo, 2001) (5)
    3. A 5 minute break every 60 minutes (Owen et al. 2009) (6)
  • Their results from this group of subjects revealed the following: participants were seated at work for an average of 5.3 hours ± 1.0 hour/day, which is equivalent to 66 ± 12% of the average working day, accrued in 27 ± 7 sitting events/day; overall, 5-20% of sitting events and 25-67% of the sitting time was accumulated in sitting events longer than current recommendations; not one worker met 20 or 30 minute recommendations for a compete working day, while 8% of participants were able to meet the 55 minute recommendation (EDITOR’S NOTE: remember that the 55 minute recommendation emerged from one research group after one study…personally I think 55 is arbitrary and far too long based on our knowledge of spinal tissue creep and load tolerance.)
  • Although the study sample was small and external validity may be limited, Ryan et al. should be commended for providing one of the only datasets like this to date. Although further research is required, it is certainly within reason that many office workers follow similar patterns, making the work environment itself an appropriate setting to target the reduction of prolonged sitting utilizing self-management strategies and reminders.
Sitting Posture in Pain-Free Subjects:
  • It has been shown that LBP patients tend to have altered proprioceptive awareness and neck pain patients have an altered sense of ideal posture. This could, in theory and practice, make implementing self-corrective exercises difficult. To date, there has been little investigation on pain-free subjects comparing actual sitting posture with patient-perceived ideals and clinician-perceived ideals, a necessary step before we extrapolate to spinal pain populations.
  • Therefore, O’Sullivan and colleagues (#2 above) aimed to investigate whether pain-free subjects can be reliably positioned in a neutral sitting posture (slight lumbar lordosis and relaxed thorax); and to compare perceptions of neutral sitting posture to habitual sitting posture (HSP).
  • 17 pain-free subjects first assumed their habitual sitting posture (HSP – “sit as you usually do”) and then their own subjectively perceived ideal sitting posture (SPIP – “sit in a posture which you think is the ideal posture”). Finally, 2 testers positioned the subjects into the tester’s perceived ideal posture (TPIP). Measurement data was collected using the Spinal Position Monitoring Device (SPMD – “Bodyguard”, Sels Instruments, Belgium – “…incorporates a strain gauge that provides information about the relative distance between anatomical landmarks, calculating spinal flexion/ extension by the degree of strain gauge elongation. Subject posture is expressed as a percentage of strain gauge elongation, so that the degree of spinal flexion/extension is expressed relative to range of motion (ROM), rather than being expressed in degrees.” [pg. 558])
  • TPIP was a ‘neutral’ spine posture with slight anterior pelvic tilting and slight lumbar lordosis with a relaxed thoracic spine. Each sitting condition was measured for a period of 5 x 1 minute intervals and the data from the middle 3 seconds of each trial was utilized in the analysis to avoid data contamination from beginning and end movements.
  • Results for HSP: This posture was significantly more flexed than the other postures, but was still a mid-range posture, indicating that pain-free subjects do not habitually sit in end range postures (as opposed to CLBP patients who have been shown to adopt near end-range provocative postures [7]) – this is the take-home point from this study.
  • Results for SPIP: Although not statistically significant, this posture, on average, was slightly more lordotic than TPIP. Thoracic extension was not measured in this study but the authors observed that patients did tend to extend this region of this spine more in this component of the study.
  • Results for TPIP: An interesting side note is that the inter-tester reliability for positioning patients into the TPIP was very high: ICC = 0.91 with only a 3.5% variance. In agreement with previous studies, these results indicate that even pain-free subjects may require cues and practice to assume neutral sitting posture, which makes the high level of reliability between clinicians promising.
  • Despite providing us with some useful and previously unstudied data, readers should keep a few things in mind. First, the neutral posture utilized in this study has not been compared systematically to other postures, it was simply the one the authors chose. Further, only sagittal orientation in an unsupported sitting posture was evaluated while measuring the lumbar spine – future studies should evaluate the whole spine in a variety of sitting positions. Lastly, this sample size was small.
Seated Posture and Lumbar Supports:
  • Forward head posture (FHP) is a common problem during routine sitting and has been identified as a risk factor for developing neck pain.
  • Some evidence suggests that ergonomic corrections of workspace setup and chair orientation can reduce neck and shoulder pain associated with long-sitting (8).
  • It is also accepted that all spinal curvatures are related and that neck posture is affected by changes in position of lower parts of the spine.
  • Lumbar rolls are commonly recommended and sold by individual practitioners to help correct sitting posture and reduce symptoms resulting from long-sitting. Despite this widespread use, there is a lack of literature evaluating the effects of these supports. Therefore, the authors of this study (#3 above) aimed to investigate whether placement of a lumbar roll while seated on an office chair influences the position of head and neck posture, more so than other typical adjustments of the chair.
  • Thirty healthy male participants (18–30 yoa) were photographed while in the ‘natural head resting position’ in each of 4 sitting positions with and without a lumbar roll in situ. Two positions incorporated adjustments to the back rest and 1 to the seat pan of the office chair. Digitized photographs were used to determine the craniovertebral (CV) angle for each participant. Comparisons between the CV angle in all postural registrations were made using a mixed model analysis adjusted for multiple comparisons.
  • To quickly boil down the analysis of the 8 experimental conditions – the only position that significantly reduced FHP was the addition of a lumbar roll with the back of the chair angled to 110°. FHP was noted to increase as the seat back was reclined. In more upright 90°positions, the addition of a lumbar roll did not significantly influence FHP, challenging the common assumption that a lumbar roll will improve neck posture.
  • Of course, a study such as this is limited by the ‘snapshot’ (literally) nature of the data collection, which cannot account for temporal changes with longer sitting periods which may include additional postural adaptations. This study was also conducted on pain-free subjects so further work needs to be done on clinical populations.

Clinical Application & Conclusions:

These three studies looked at different aspects of sitting in an occupational setting and each adds useful information to our body of knowledge. The take home points of these studies can be summarized as follows:
  1. Ryan and colleagues (#1 above) showed us that office workers are likely sitting in stints that are too long for optimal health. Despite the controversy on how long is too long, not even one subject in their study stood up or moved around at even 30 minute intervals for an entire work day! As evidence-informed clinicians who are mindful of soft tissue strain, passive tissue creep and spinal loading profiles, we should be encouraging our patients to stand up and perform some type of postural relief exercise or movement at least once every 30 minutes (see below).
  2. O’Sullivan and colleagues (#2 above) showed us that even pain-free subjects, when left to their own habits, tend to sit in more flexion than when they are instructed to sit in an ideal posture or positioned by a clinician. This strengthens the need for us to assist and educate our patients about ideal sitting posture and provide them with cues and tools to assist in this process. If pain-free people need help, imagine what back and neck pain patients need! This study also provides some data for comparison purposes when spinal pain populations are studied in more detail.
  3. Lastly, Horton and colleagues (#3 above) challenged the common perception that lumbar rolls have an independently positive effect on neck posture during sitting, showing us that, at least in this pain-free population, the addition of a lumbar roll only seems to help improve forward head posture when the seat back is reclined to 110°. Again, further research is required in clinical populations.
I normally put office ergonomic recommendations into the same ‘evidence category’ as pillow and mattress recommendations – the literature as a whole simply can’t guide us very well. Sometimes in practice we must made recommendations based on our clinical experience and intuition. There is nothing wrong with this, as long as we take the existing evidence and patient preferences into consideration as well. This is what evidence-informed practice is! I think the best service we can provide to our desk-bound patients at this point is a STRONG recommendation to implement a purposeful, consistent program of postural relief movements such as the Brügger Postural Relief exercise described below. This movement is designed to reverse chronic tissue and postural strain, while promoting deeper breathing and relaxation. Although there is some variation on how to do this movement, below are some points I find helpful with my patients:
  • Externally rotate the arms, point the thumbs backwards to open up the chest
  • Retract and depress the shoulder blades (I often say “tuck them in your back pockets”)
  • Gently extend the entire spine (“look up, shoulders back”) and instruct the patient to take a purposeful, DEEP breath “make your ribcage as big as you can”)…hold this deep breath in for a few seconds and slowly return to neutral position during exhalation
  • Repeat 2-4 times per hour at work and take a drink of water each time (this is a helpful cue to get people to hydrate properly at work as well!
Brugger PRP

Additional References:

  1. Lis A, Black K, Korn H, Nordin M. Association between sitting and occupational LBP. European Spine Journal 2007;16:283-98.
  2. O’Sullivan P. Diagnosis and classification of chronic low back pain disorders: maladaptive movement and motor control impairments as underlying mechanism. Manual Therapy 2005; 10(4): 242-55.
  3. Katzmarzyk PT et al. Sitting time and mortality from all causes, cardiovascular disease, and cancer. Medicine and Science in Sports and Exercise 2009; 41(5): 998–1005.
  4. Chartered Society of Physiotherapy, 2005. Fit to work: CSP public information leaflet 2005 [online]. London, UK: Chartered Society of Physiotherapy. Available from: http://csp.org.uk/uploads/documents/CSP_FTW_inside_v21.pdf [Accessed 9 February 2010].
  5. Atlas SJ & Deyo RA. Evaluating and managing acute low back pain in the primary care setting. Journal of General Internal Medicine 2001; 16(2): 120–131.
  6. Owen N, Bauman A & Brown W. Too much sitting: a novel and important predictor of chronic disease risk. British Journal of Sports Medicine 2009; 43(2): 81–83.
  7. Dankaerts W, O’Sullivan PB, Burnett A, Straker LM. Differences in sitting postures are associated with non-specific chronic low back pain disorders when subclassified. Spine 2006b; 31(6): 698-704.
  8. Rempel DM, Wang P-C, Janowitz I et al. A randomized controlled trial evaluating the effects of new task chairs on shoulder and neck pain among sewing machine operators: the Los Angeles garment study. Spine 2007; 32: 931–8.