Sitting

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The Thinker by Auguste Rodin Universita di louisville, il pensatore di rodin 02.jpg
The Thinker by Auguste Rodin

Sitting is a basic action and resting position in which the body weight is supported primarily by the bony ischial tuberosities with the buttocks in contact with the ground or a horizontal surface such as a chair seat, instead of by the lower limbs as in standing, squatting or kneeling. When sitting, the torso is more or less upright, although sometimes it can lean against other objects for a more relaxed posture.

Contents

Sitting for much of the day may pose significant health risks, with one study suggesting people who sit regularly for prolonged periods may have higher mortality rates than those who do not. [1] [2] The average person sits down for 4.7 hours per day, according to a global review representing 47% of the global adult population. [3]

The form of kneeling where the buttocks sit back on the heels, for example as in the Seiza and Vajrasana postures, is also often interpreted as sitting.

Prevalence

The British Chiropractic Association said in 2006 that 32% of the British population spent more than ten hours per day sitting down. [4]

Positions

On the floor

A man sitting on the ground, on a road in Nepal A man sitting on the back of Road during lockdown-Shambhunath Municipality , Nepal-4556.jpg
A man sitting on the ground, on a road in Nepal

The most common ways of sitting on the floor involve bending the knees. One can also sit with the legs unbent, using something solid as support for the back or leaning on one's arms. Sitting with bent legs can be done with the legs mostly parallel or by crossing them over each other.

A common cross-legged position is with the lower part of both legs folded towards the body, crossing each other at the ankle or calf, with both ankles on the floor, sometimes with the feet tucked under the knees or thighs. The position is known in several European languages as tailor's posture, from the traditional working posture of tailors; [5] compare tailor's bunion. It is also named after various plains-dwelling nomads: in American English Indian style (Note: This name might be considered offensive), [6] in many European languages "Turkish style", and in Japanese agura ( 胡座 , The sitting style of non-Han ethnics (particularly Turks, Mongols and other Central Asians.)). In yoga it is known as sukhasana, meaning "easy pose."

On a raised seat

A woman sitting on a chair 1999-Anna Meacci.jpg
A woman sitting on a chair

Various raised surfaces at the appropriate height can be used as seats for humans, whether they are made for the purpose, such as chairs, stools and benches, or not. While the buttocks are nearly always rested on the raised surface, there are many differences in how one can hold one's legs and back.

There are two major styles of sitting on a raised surface. The first has one or two of the legs in front of the sitting person; in the second, sitting astride something, the legs incline outwards on either side of the body.

An Indian Buddha, seated with legs crossed Buddhist bronze sculpture NMND.JPG
An Indian Buddha, seated with legs crossed

The feet can rest on the floor or on a footrest, which can keep them vertical, horizontal, or at an angle in between. They can also dangle if the seat is sufficiently high. Legs can be kept right to the front of the body, spread apart, or one crossed over the other.

The upper body can be held upright, recline to either side or backward, or one can lean forward.

Yoga, traditions and spirituality

The Japanese tea ceremony is performed sitting in seiza. Tea ceremony performing 2.jpg
The Japanese tea ceremony is performed sitting in seiza.

There are many seated positions in various traditions and rituals. Four examples are:

In various mythologies and folk magic, sitting is a magical act that connects the person who sits with other persons, states or places. [7]

Kneeling chairs

The kneeling chair (often just referred to as "ergonomic chair") was designed to motivate better posture than the conventional chair.[ qualify evidence ] To sit in a kneeling chair, one rests one's buttocks on the upper sloping pad and rests the front of the lower legs atop the lower pad, i.e., the human position as both sitting and kneeling at the same time.

Health risks

Back of a sitting nude by school of Rembrandt School of Rembrandt - Sitting nude.jpg
Back of a sitting nude by school of Rembrandt

In 1700, De Morbis Artificum Diatriba listed sitting in odd postures as a cause of diseases in "chair-workers". [8] Current studies indicate there is a significantly higher mortality rate among people who regularly sit for prolonged periods, and the risk is not negated by regular exercise, though it is lowered. [1] [9] The causes of mortality and morbidity include heart disease, obesity, type 2 diabetes and cancer, specifically, breast, endometrial, colorectal, lung, and epithelial ovarian cancer. [1] [9] [10] [11] [12] The link between heart disease and diabetes mortality and sitting is well-established, but the risk of cancer mortality is unclear. [11] [13] Sedentary time is also associated with an increased risk of depression in children and adolescents. [14] A correlation between occupational sitting specifically and higher body mass index has been demonstrated, but causality has not yet been established. [9] There are several hypotheses explaining why sitting is a health risk. These include changes in cardiac output, vitamin D, inflammation, sex hormone activity, lipoprotein lipase activity, and GLUT4 activity due to long periods of muscular unloading, among others. [9] [11] [12]

Sitting may occupy up to half of an adult's workday in developed countries. [9] Workplace programs to reduce sitting vary in method. They include sit-stand desks, counseling, workplace policy changes, walking or standing meetings, treadmill desks, breaks, therapy ball chairs, and stepping devices. [10] [15] Results of these programs are mixed, [10] but there is moderate evidence to show that changes to chairs (adjusting the biomechanics of the chair or using different types of chairs) can effectively reduce musculoskeletal symptoms in workers who sit for most of their day. [16]

Public health programs typically focus on increasing physical activity rather than reducing sitting time. [1] [17] One major target for these public health programs is sitting in the workplace. [10] [15] For example, WHO Europe recommended in September 2015 the provision of adjustable desks in the workplace. [17] In general, there is conflicting evidence regarding the precise risks of sitting for long periods. [9] A 2018 Cochrane review found low-quality evidence that providing employees with a standing desk option may reduce the length of time some people sit at work in the first year. [15] This reduction in sitting may decrease with time, and there is no evidence that standing desks are effective in the long term. [15] In addition, a 2018 British Journal of Medicine systematic review concluded that interventions aimed at reducing sitting outside of work were only modestly effective. [18] It is not clear how standing desks compare to other work-place interventions to reduce the length of time employees are sitting during the work day. [15]

Relationship between posture and health conditions

Though most studies even until early 21st century relate human body postures to various musculoskeletal conditions, recent researches show no potential causal relationship between postures and these conditions like back pain; [19] other causes like sleep deprivation, stress and long-term physical inactivity or prolonged static unnatural postural stress could be significant confounders for various health conditions. [20] However some research show that prolonged slouched position may be a cause for minor breathing disorders. [21] Though still a large proportion of the clinical practitioners attribute absence of a neutral spine posture as one of the main causes of conditions like back pain and neck pain, the relationship is not thoroughly established.[ citation needed ] It is also thought that much of so-called "poor posture" is actually just postural stress and being stuck with bad ergonomics that could be causing the pain — not really a postural problem. [22] iHunch is an example of postural stress which could cause upper back pain and neck pain, which is prevalent in younger generations and people whose occupation involves prolonged usage of computers.

Sedentary behaviour

Women reclining in chairs. Painting by Jean-Francois de Troy. DeTroy.jpg
Women reclining in chairs. Painting by Jean-François de Troy.

Sedentary behaviour is any waking behaviour, whether in sitting or reclining posture, by an energy expenditure less or equal to 1.5 metabolic equivalents of task (METs). [23] MET, beside the watt and kilojoules, is the unit for expressing the energy cost of physical activities. One MET is defined as resting metabolic rate – as energy used with a person at rest, sitting quietly in a chair or as the amount of O2 consumed with that person. [24] MET for an adult weighing 70 kg equals 3.5 ml O2 per kg body weight per min. [25]

Sedentary behaviour should be distinguished from being inactive – performing insufficient amounts of MVPA (moderate to vigorous physical activity). [26] The World Health Organization [27] recommends at least 60 min of daily MVPA for children and adolescents aged 5–17 years, and 150 min of weekly MVPA for adults.

Sedentary behaviour can not be equated with screen time, although some researchers found out that a large share of waking time by children and adolescents in a sedentary position is accumulated by media consumption in front of a screen. [28]

See also

Related Research Articles

<span class="mw-page-title-main">Repetitive strain injury</span> Medical condition

A repetitive strain injury (RSI) is an injury to part of the musculoskeletal or nervous system caused by repetitive use, vibrations, compression or long periods in a fixed position. Other common names include repetitive stress injury, repetitive stress disorders, cumulative trauma disorders (CTDs), and overuse syndrome.

<span class="mw-page-title-main">White-collar worker</span> Social class; person who performs intellectual labor

A white-collar worker is a person who performs professional service, desk, managerial, or administrative work. White-collar work may be performed in an office or other administrative setting. White-collar workers include job paths related to government, consulting, academia, accountancy, business and executive management, customer support, design, economics, engineering, market research, finance, human resources, operations research, marketing, public relations, information technology, networking, law, healthcare, architecture, and research and development. In contrast: blue-collar workers perform manual labor or work in skilled trades; pink-collar workers work in care, health care, social work, or teaching; and grey-collar jobs combine manual labor and skilled trades with non-manual or managerial duties.

<span class="mw-page-title-main">Standing desk</span> Desk used standing

A standing desk or stand-up desk is a desk conceived for writing, reading or drawing while standing up or while sitting on a high stool.

<span class="mw-page-title-main">Sedentary lifestyle</span> Type of lifestyle involving little or no physical activity

Sedentary lifestyle is a lifestyle type, in which one is physically inactive and does little or no physical movement and or exercise. A person living a sedentary lifestyle is often sitting or lying down while engaged in an activity like socializing, watching TV, playing video games, reading or using a mobile phone or computer for much of the day. A sedentary lifestyle contributes to poor health quality, diseases as well as many preventable causes of death.

<span class="mw-page-title-main">Hip fracture</span> Broken bone in hip joint region

A hip fracture is a break that occurs in the upper part of the femur, at the femoral neck or (rarely) the femoral head. Symptoms may include pain around the hip, particularly with movement, and shortening of the leg. Usually the person cannot walk.

<span class="mw-page-title-main">Physical activity</span> Any voluntarily bodily motion produced by skeletal muscles and requires energy expenditure

Physical activity is defined as any voluntary bodily movement produced by skeletal muscles that requires energy expenditure. Physical activity encompasses all activities, at any intensity, performed during any time of day or night. It includes both exercise and incidental activity integrated into daily routine. This integrated activity may not be planned, structured, repetitive or purposeful for the improvement of fitness, and may include activities such as walking to the local shop, cleaning, working, active transport etc. Lack of physical activity is associated with a range of negative health outcomes, whereas increased physical activity can improve physical and mental health, as well as cognitive and cardiovascular health. There are at least eight investments that work to increase population-level physical activity, including whole-of-school programmes, active transport, active urban design, healthcare, public education and mass media, sport for all, workplaces and community-wide programmes. Physical activity increases energy expenditure and is a key regulator in controlling body weight.

<span class="mw-page-title-main">Cancer survivor</span> Person with cancer who is still alive

A cancer survivor is a person with cancer of any type who is still living. Whether a person becomes a survivor at the time of diagnosis or after completing treatment, whether people who are actively dying are considered survivors, and whether healthy friends and family members of the cancer patient are also considered survivors, varies from group to group. Some people who have been diagnosed with cancer reject the term survivor or disagree with some definitions of it.

<span class="mw-page-title-main">Musculoskeletal disorder</span> Medical condition

Musculoskeletal disorders (MSDs) are injuries or pain in the human musculoskeletal system, including the joints, ligaments, muscles, nerves, tendons, and structures that support limbs, neck and back. MSDs can arise from a sudden exertion, or they can arise from making the same motions repeatedly repetitive strain, or from repeated exposure to force, vibration, or awkward posture. Injuries and pain in the musculoskeletal system caused by acute traumatic events like a car accident or fall are not considered musculoskeletal disorders. MSDs can affect many different parts of the body including upper and lower back, neck, shoulders and extremities. Examples of MSDs include carpal tunnel syndrome, epicondylitis, tendinitis, back pain, tension neck syndrome, and hand-arm vibration syndrome.

Active sitting is the practice of enabling or encouraging individuals to engage in physical activity while seated. It is also commonly known as dynamic sitting. The underlying notion highlights the advantages of incorporating flexibility and movement while sitting, as it can positively impact the human body and allow the completion of certain tasks that require sitting. "Active sitting, consisting of modified chairs or stability balls, allows the body to stay dynamic while seated." One of the earliest forms of active sitting is the common rocking chair which allows forward and backward swaying motion.

<span class="mw-page-title-main">Patellofemoral pain syndrome</span> Medical condition

Patellofemoral pain syndrome is knee pain as a result of problems between the kneecap and the femur. The pain is generally in the front of the knee and comes on gradually. Pain may worsen with sitting, excessive use, or climbing and descending stairs.

The complications of prolonged standing are conditions that may arise after standing, walking, or running for prolonged periods. Many of the complications come from prolonged standing that is repeated several times a week. Many jobs require prolonged standing, such as "retail staff, baristas, bartenders, assembly line workers, security staff, engineers, catering staff, library assistants, hair stylists and laboratory technicians". The basic physiological change that occurs in the body during prolonged standing or sudden stand from supine position is that there will be increased pooling of blood in the legs. This decreases the venous return, and so there will be decreased cardiac output, which ultimately causes systolic blood pressure to fall (hypotension). This hypotension may lead the subject to faint or to have other symptoms of hypotension. Standing requires about 10% more energy than sitting.

<span class="mw-page-title-main">Treadmill desk</span>

A treadmill desk, walking desk or treadmill workstation is a computer desk that is adapted so that the user walks on a treadmill while performing office tasks. Persons using a treadmill desk seek to change the sedentary lifestyle associated with being an office worker and to integrate gentle exercise into their working day.

<span class="mw-page-title-main">Falling (accident)</span> Cause of injury or death

Falling is the action of a person or animal losing stability and ending up in a lower position, often on the ground. It is the second-leading cause of accidental death worldwide and a major cause of personal injury, especially for the elderly. Falls in older adults are a major class of preventable injuries. Construction workers, electricians, miners, and painters are occupations with high rates of fall injuries.

<span class="mw-page-title-main">Musculoskeletal injury</span> Medical condition

Musculoskeletal injury refers to damage of muscular or skeletal systems, which is usually due to a strenuous activity and includes damage to skeletal muscles, bones, tendons, joints, ligaments, and other affected soft tissues. In one study, roughly 25% of approximately 6300 adults received a musculoskeletal injury of some sort within 12 months—of which 83% were activity-related. Musculoskeletal injury spans into a large variety of medical specialties including orthopedic surgery, sports medicine, emergency medicine and rheumatology.

This article is about physical therapy in carpal tunnel syndrome.

Workplace health promotion is the combined efforts of employers, employees, and society to improve the mental and physical health and well-being of people at work. The term workplace health promotion denotes a comprehensive analysis and design of human and organizational work levels with the strategic aim of developing and improving health resources in an enterprise. The World Health Organization has prioritized the workplace as a setting for health promotion because of the large potential audience and influence on all spheres of a person's life. The Luxembourg Declaration provides that health and well-being of employees at work can be achieved through a combination of:

<span class="mw-page-title-main">Ergonomics</span> Designing systems to suit their users

Ergonomics, also known as human factors or human factors engineering (HFE), is the application of psychological and physiological principles to the engineering and design of products, processes, and systems. Primary goals of human factors engineering are to reduce human error, increase productivity and system availability, and enhance safety, health and comfort with a specific focus on the interaction between the human and equipment.

Total Worker Health is a trademarked strategy defined as policies, programs, and practices that integrate protection from work-related safety and health hazards with promotion of injury and illness prevention efforts to advance worker well-being. It was conceived and is funded by the National Institute for Occupational Safety and Health (NIOSH). Total Worker Health is tested and developed in six Centers of Excellence for Total Worker Health in the United States.

Non-exercise activity thermogenesis (NEAT), also known as non-exercise physical activity (NEPA), is energy expenditure during activities that are not part of a structured exercise program. NEAT includes physical activity at the workplace, hobbies, standing instead of sitting, walking around, climbing stairs, doing chores, and fidgeting. Besides differences in body composition, it represents most of the variation in energy expenditure across individuals and populations, accounting from 6-10 percent to as much as 50 percent of energy expenditure in highly active individuals.

References

  1. 1 2 3 4 Biswas, A; Oh, PI; Faulkner, GE; Bajaj, RR; Silver, MA; Mitchell, MS; Alter, DA (2015). "Sedentary Time and Its Association With Risk for Disease Incidence, Mortality, and Hospitalization in Adults: A Systematic Review and Meta-analysis". Annals of Internal Medicine. 162 (2): 123–32. doi:10.7326/M14-1651. PMID   25599350. S2CID   7256176.
  2. ↑ Mole, Beth (2017-09-13). "The new study suggesting sitting will kill you is kind of a raging dumpster fire". Ars Technica. Retrieved 2021-01-20.
  3. ↑ on behalf of the Sedentary Behaviour Council Global Monitoring Initiative Working Group; Mclaughlin, M.; Atkin, A. J.; Starr, L.; Hall, A.; Wolfenden, L.; Sutherland, R.; Wiggers, J.; Ramirez, A.; Hallal, P.; Pratt, M. (December 2020). "Worldwide surveillance of self-reported sitting time: a scoping review". International Journal of Behavioral Nutrition and Physical Activity. 17 (1): 111. doi: 10.1186/s12966-020-01008-4 . ISSN   1479-5868. PMC   7469304 . PMID   32883294.
  4. ↑ "Sitting straight 'bad for backs'". BBC. November 28, 2006. Retrieved February 20, 2015.
  5. ↑ "The Art of the Cut". History.org. Archived from the original on August 5, 2007. Retrieved 2012-03-16.
  6. ↑ Larson, David E. (1976-03-15). "Sitting Posture of Children". JAMA. 235 (11): 1106. doi:10.1001/jama.1976.03260370016009. ISSN   0098-7484.
  7. ↑ Čajkanović, Veselin (1996). Translated by Živković, Marko. "Magical Sitting". Anthropology of East Europe Review. 14 (1). Archived from the original on 2007-07-03. Retrieved 2007-07-09. It is obvious from all the above that sitting, seen from the viewpoint of the history of religion, could be a magical act which, within the framework of analogic magic, will establish a certain relationship, a covenant.
  8. ↑ Ramazzini, B. (2001). "De Morbis Artificum Diatriba Diseases of Workers". American Journal of Public Health. 91 (9): 1380–1382. doi:10.2105/AJPH.91.9.1380. PMC   1446785 . PMID   11527762.
  9. 1 2 3 4 5 6 van Uffelen, Jannique G. Z.; Wong, Jason; Chau, Josephine Y.; van der Ploeg, Hidde P.; Riphagen, Ingrid; Gilson, Nicholas D.; Burton, Nicola W.; Healy, Genevieve N.; Thorp, Alicia A. (Oct 2010). "Occupational sitting and health risks: a systematic review". American Journal of Preventive Medicine. 39 (4): 379–388. doi:10.1016/j.amepre.2010.05.024. ISSN   1873-2607. PMID   20837291. S2CID   205433800.
  10. 1 2 3 4 Chau, Josephine Y.; der Ploeg, Hidde P. van; van Uffelen, Jannique G. Z.; Wong, Jason; Riphagen, Ingrid; Healy, Genevieve N.; Gilson, Nicholas D.; Dunstan, David W.; Bauman, Adrian E. (Nov 2010). "Are workplace interventions to reduce sitting effective? A systematic review". Preventive Medicine. 51 (5): 352–356. doi:10.1016/j.ypmed.2010.08.012. ISSN   1096-0260. PMID   20801153.
  11. 1 2 3 Proper, Karin I.; Singh, Amika S.; van Mechelen, Willem; Chinapaw, Mai J. M. (Feb 2011). "Sedentary behaviors and health outcomes among adults: a systematic review of prospective studies". American Journal of Preventive Medicine. 40 (2): 174–182. doi:10.1016/j.amepre.2010.10.015. ISSN   1873-2607. PMID   21238866.
  12. 1 2 Lynch, Brigid M. (Nov 2010). "Sedentary behavior and cancer: a systematic review of the literature and proposed biological mechanisms". Cancer Epidemiology, Biomarkers & Prevention. 19 (11): 2691–2709. doi:10.1158/1055-9965.EPI-10-0815. ISSN   1538-7755. PMID   20833969. S2CID   1026991.
  13. ↑ Wilmot, E. G.; Edwardson, C. L.; Achana, F. A.; Davies, M. J.; Gorely, T.; Gray, L. J.; Khunti, K.; Yates, T.; Biddle, S. J. H. (14 August 2012). "Sedentary time in adults and the association with diabetes, cardiovascular disease and death: systematic review and meta-analysis" (PDF). Diabetologia. 55 (11): 2895–2905. doi:10.1007/s00125-012-2677-z. PMID   22890825. S2CID   24453607.
  14. ↑ Liu, M; Wu, L; Yao, S (9 November 2015). "Dose-response association of screen time-based sedentary behaviour in children and adolescents and depression: a meta-analysis of observational studies". British Journal of Sports Medicine. 50 (20): 1252–1258. doi:10.1136/bjsports-2015-095084. PMC   4977203 . PMID   26552416.
  15. 1 2 3 4 5 Shrestha, Nipun; Kukkonen-Harjula, Katriina T.; Verbeek, Jos H.; Ijaz, Sharea; Hermans, Veerle; Pedisic, Zeljko (17 December 2018). "Workplace interventions for reducing sitting at work". The Cochrane Database of Systematic Reviews. 2018 (12): CD010912. doi:10.1002/14651858.CD010912.pub5. ISSN   1469-493X. PMC   6517221 . PMID   30556590.
  16. ↑ van Niekerk, Sjan-Mari; Louw, Quinette Abigail; Hillier, Susan (2012). "The effectiveness of a chair intervention in the workplace to reduce musculoskeletal symptoms. A systematic review". BMC Musculoskeletal Disorders. 13: 145. doi: 10.1186/1471-2474-13-145 . ISSN   1471-2474. PMC   3552974 . PMID   22889123.
  17. 1 2 Europe, WHO (September 2015). "World Health Organization" (PDF). WHO. Retrieved October 7, 2015.
  18. ↑ Shrestha, N; Grgic, J; Weisner, G; Parker, A; Podnar, H; Bennie, J; Biddle, SJH; Pedisic, Zeljko (13 January 2018). "Effectiveness of interventions for reducing non-occupational sedentary behaviour in adults and older adults: a systematic review and meta-analysis" (PDF). British Journal of Sports Medicine. 53 (19): bjsports–2017–098270. doi:10.1136/bjsports-2017-098270. PMID   29331992. S2CID   3291752.
  19. ↑ Lederman, Eyal (April 2011). "The fall of the postural-structural-biomechanical model in manual and physical therapies: exemplified by lower back pain". Journal of Bodywork and Movement Therapies. 15 (2): 131–138. doi:10.1016/j.jbmt.2011.01.011. ISSN   1532-9283. PMID   21419349.
  20. ↑ "Are you sitting comfortably: the myth of good posture". The Guardian. 5 March 2018.
  21. ↑ Albarrati, Ali; Zafar, Hamayun; Alghadir, Ahmad H.; Anwer, Shahnwaz (2018). "Effect of Upright and Slouched Sitting Postures on the Respiratory Muscle Strength in Healthy Young Males". BioMed Research International. 2018: 3058970. doi: 10.1155/2018/3058970 . PMC   5845520 . PMID   29682532.
  22. ↑ "Posture Correction: Does it matter?".
  23. ↑ Sedentary Behaviour, Research Network. "Letter to the editor: Standardized use of the terms "sedentary" and "sedentary behaviours"". Applied Physiology, Nutrition, and Metabolism. 37 (3): 540–542.
  24. ↑ Jette, M.; Sidney, K.; Blümchen, G. (1990). "Metabolic equivalents (METS) in exercise testing, exercise prescription, and evaluation of functional capacity". Clinical Cardiology. 13 (8): 555–65. doi:10.1002/clc.4960130809. PMID   2204507. S2CID   23629878.
  25. ↑ Adamo, Kristi B.; Prince, Stephanie A.; Tricco, Andrea C.; Connor-Gorber, Sarah; Tremblay, Mark (2009). "A comparison of indirect versus direct measures for assessing physical activity in the pediatric population: A systematic review". International Journal of Pediatric Obesity. 4 (1): 2–27. doi:10.1080/17477160802315010. PMID   18720173.
  26. ↑ Sturm, David J.; Kelso, Anne; Kobel, Sussane; Demetriou, Yolanda (2020). "Physical activity levels and sedentary time during school hours of 6th-grade girls in Germany". Journal of Public Health: From Theory to Practice. 29 (4): 847–855. doi: 10.1007/s10389-019-01190-1 . S2CID   210158026.
  27. ↑ "WHO 2011". Archived from the original on November 16, 2011.
  28. ↑ Huber, Gerhard; Koppel, Maximilian (2017). "Analyse der Sitzzeiten von Kindern und Jugendlichen zwischen 4 und 20 Jahren". DZSM. 2017 (4): 101–106. doi: 10.5960/dzsm.2017.278 .

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