Guest blog by David Bernardi, Ergonomic Consultant, President of Summit Ergonomics

Part three of a three-part series
The science supporting the health benefits of reducing sedentarism in the workplace is well documented.^{1, 2} Several chronic disease states can be attributed to an inactive lifestyle, including the four most impactful on life expectancy; type 2 diabetes, obesity, cardiovascular disease, and cancer.³ Let’s take a look at how proper utilization of a sit-stand desk can potentially impact one’s health.

Physiologic Benefits

Better Posture for Better Breathing

When standing, one can engage the diaphragm muscle more efficiently for proper breathing technique. Diaphragmatic breathing increases blood oxygen levels substantially by allowing for deeper breaths where oxygen exchange is 5-7X more efficient in the lower aspects of the lung⁴. When sitting we typically adopt a chest breathing strategy which primarily engages the upper 1/3 of the lung and is far less efficient, resulting in less oxygen for the tissues, organs and brain. This may result in fatigue, increased respiration and a higher pulse rate. Chest breathing also taxes the postural muscles of the ribs, upper back and chest. Since these muscles are not intended for active contraction, they can quickly fatigue, leading to insufficient blood flow where painful trigger points can possibly form resulting in chronic pain and irritation.⁵

Post-meal standing/walking

Standing/movement after meals can reduce blood glucose levels by up to 50%⁶. The simple act of standing for 15-20 minutes after arriving at the office and after lunch can be an effective strategy for reducing blood sugars in high risk employees. Each percentage point decrease in A1c (average blood sugar) reduces the risk of eye, kidney, and nerve diseases by 40%⁷.

Muscle Contraction

Contraction of the postural muscles that occurs during transition from sit to stand releases Lipoprotein Lipase (LPL) enzyme which facilitates the breakdown of triglycerides (fats) and increases in HDL cholesterol (ie “the good cholesterol”). LPL levels decrease significantly after just one day of inactivity.⁸ Control of cholesterol levels can reduce cardiovascular complications by 20–50%⁹. The health benefit of frequent sit to stand transition has been well documented by Vernikos¹⁰. Additionally, contraction of the lower extremity muscles stimulated by active standing coupled with foot contact forces has been shown to increase blood flow wave action to the brain¹¹.

Active Standing

Non-Exercise Activity-based Thermogenesis, aka “NEAT”, is a concept described by Levine et al¹². On average, active standing burns 0.7-0.8 calories extra per minute¹³. It has been shown that non-obese individuals have higher levels of NEAT in their lives¹⁴. Incorporating just 30 min of activity into the workday can reduce the risk of developing various disease states including cardiovascular disease and type-2 diabetes.¹⁵

Relax Hip Flexor Tightness

Excessive sitting leads to chronically shortened hip flexor muscles which can create low back pain (LBP) by excessively rotating the pelvis. Hip flexor tightness may also significantly impact stress levels in the body. The hip flexor is a “Fight or Flight” muscle group, with a direct link to the amygdala of the brain. As a result, tight hip flexors can lead to increased release of the stress hormone cortisol¹⁶. Excessive cortisol levels can affect an individual’s mental health, and mental health has become a huge financial burden to business¹⁷. The presence of cortisol has also been shown to inhibit insulin function in the body¹⁸, the substance necessary for processing sugars in the bloodstream, thereby leading to excess fat storage and possibly diabetes.

Ergonomic Benefit

Proper Hand Positioning for Sitting & Standing

The ability to position a worksurface at proper hand position is a key for relaxing the trapezius, upper back, shoulder and neck musculature. Using a worksurface that is positioned too high requires a constant contraction of these muscles to support the hands in an elevated position. Chronic muscle tension can lead to a host of musculoskeletal disorders including trigger points, thoracic outlet syndrome, headaches and/or migraines and numbness & tingling in the arms.

Increased Blood Flow

Since standard desks are too tall for the majority of the population, many workers must raise their chair to a height in which their feet are no longer able to touch the floor. Even with a footrest, there is an increased tendency to sway the feet back and rest them on the chair base. One may also lean forward in their chair to get one’s hands high enough to interact with the computer and effectively view the monitor, leading to a forward hunch with closed angles (less than 90◦) at the waist and elbows. Using the analogy of a garden hose, picture how the water stops flowing when you kink it. This positioning of the body will provide greater vascular resistance which means the heart must work harder to circulate blood, thereby increasing blood pressure. A well-configured sit-stand desk with proper height range for the user eliminates these issues.

Reduced Disc Compression

Standing upright significantly reduces compressive forces in the spine. For comparison sake, compressive forces when sitting in the traditional 90-90-90 “ergonomic” position are about 40% higher than standing.¹⁹. When seated in the forward hunch position as described in the previous paragraph, the forces are about 70% higher than standing.²⁰ For individuals with Low Back Pain (LBP), which is reportedly 11% of the population,²¹ providing proper ergonomics including Sit-Stand capability with the ability to change posture, resulted in a significant reduction in pain levels.²²

Effects of Sit-Stand on Productivity

There have been many papers and studies claiming productivity increases as a result of sit-stand desk implementation. Garrett and colleagues²³ recently reported a 46% increase in productivity within a call center environment. 25 research studies reviewed by members of the Puget Sound HFES showed a mean increase in productivity of 12% with the highest study reporting 64%.²⁴ Callaghan et al reviewed eight studies of sit-stand usage and concluded three showed good evidence of significant productivity increase, four did not show significance, and one was inconclusive with the overall conclusion was that sit-stand does not adversely affect productivity.²⁵

Hopefully this summary of the medical literature helps one understand the benefits that a properly deployed and utilized sit-stand desk can provide both for ergonomics and for wellness. Frequent transitioning with a device that reaches the proper range for the user is key to maximizing the benefit.

About the Author: David Bernardi has a master’s degree in bioengineering and is currently an ergonomic consultant and president of Summit Ergonomics in Manchester NH.

References

1. Loitz C, Walker J, Potter R, Johnston N. Systematic review of workplace physical activity and sedentary behaviour interventions. PROSPERO 2015:CRD42015019398^p
2. Physical Activity in the Workplace A Guide for Employers Workplace Health Research Network, which is supported by Cooperative Agreement Number 3U48DP005045 from the Centers for Disease Control and Prevention’s Prevention Research Centers Program.
3. Ann Clin Lab Sci Summer 2012 vol. 42 no. 3 320-337 Knight, JA
4. West, JB. Respiratory Physiology: The Essentials 9th edition 2012 Lippincott Wiliams & Wilkins, Baltimore MD
5. Gerwin RD, Dommerholt J, Shah JP. An expansion of Simons’ integrated hypothesis of trigger point formation. Curr Pain Headache Rep. 2004 Dec;8(6):468–75
6. Buckley JP, Mellor DD, Morris M, et al Standing-based office work shows encouraging signs of attenuating post-prandial glycaemic excursion. Occup Environ Med Occup Environ Med. 2014 Feb;71(2):109-11.
7. http://diabetes.niddk.nih.gov/dm/pubs/statistics/index.htm.
8. Hamilton, MT, Hamilton DG et al. Role of Low Energy Expenditure and Sitting in Obesity, Metabolic Syndrome, Type 2 Diabetes, and Cardiovascular Disease Diabetes 56:2655–2667, 2007
9. http://ndep.nih.gov/media/2005_National_Diabetes_Fact_Sheet.pdf
10. Sitting Kills, Movement Heals Vernikos, Joan
11. https://www.sciencedaily.com/releases/2017/04/170424141340.htm
12. Levine JA Non-exercise activity thermogenesis (NEAT). Best Pract Res Clin Endocrinol Metab. 2002 Dec;16(4):679-702.
13. Buckley JP, Mellor DD, Morris M, et al Standing-based office work shows encouraging signs of attenuating post-prandial glycaemic excursion. Occup Environ Med Occup Environ Med. 2014 Feb;71(2):109-11.
14. Levine JA Diabetologia. 2015 August ; 58(8): 1751–1758. doi:10.1007/s00125-015-3624-6.
15. Warburton DER, Nicol CW, and Bredin, SSD. Health benefits of physical activity: the evidence 2006 Mar 14; 174(6): 801–809
16. https://bodydivineyoga.wordpress.com/2011/03/23/the-psoas-muscle-of-the-soul/
17. https://www.inc.com/matthew-jones/how-mental-health-can-save-businesses-225-billion-each-year.html
18. Vogelzangs N Urinary cortisol and six-year risk of all-cause and cardiovascular mortality. J Clin Endocrinol Metab. 2010 Nov;95(11):4959-64
19. Nachemson A, Elfström G. Intravital dynamic pressure measurements in lumbar discs. A study of common movements, maneuvers and exercises. Scand J Rehabil Med Suppl. 1970;1:1-40.
20. Ibid
21. Integrated Benefits Institute, Health and Productivity Impact of Chronic Conditions, Back Pain https://ibiweb.org/research-resources/detail/health-and-productivity-impact-of-chronic-conditions-back-pain
22. Ognibene GT1, Torres W, von Eyben R, Horst KC. Impact of a Sit-Stand Workstation on Chronic Low Back Pain: Results of a Randomized Trial J Occup Environ Med. 2016 Mar;58(3):287-93
23. Garrett G, Benden M, Mehta R, Pickens A, Camille Peres, S & Zhao H Call Center Productivity Over 6 Months Following a Standing Desk Intervention, IIE Transactions on Occupational Ergonomics and Human Factors, 4:2-3, 188-195,
24. Goggins RW, Spielholz P, Nothstein GL. Estimating the effectiveness of ergonomics interventions through case studies: implications for predictive cost-benefit analysis. J Safety Res. 2008;39(3):339-44.
25. Karakolis T, Callaghan JP. The impact of sit-stand office workstations on worker discomfort and productivity: a review. Appl Ergon. 2014 May;45(3):799-806