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What is Your Inclination . . . (ergonomically)?

The Scandinavian Journal of Rehab. Medicine 15:197-203, 1983. “Posture of the Trunk when Sitting on Forward-Inclining Seats,” written by Tom Bendix and Fin Biering-Sorensen from The Laboratory for Back Research, University of Copenhagen, Denmark:

Forward Inclination & Lumbar Lordosis

The above-mentioned study states: “Changes in posture during one hour of sitting were measured by a statometric method on 10 subjects. Four seats were used, one horizontal and three with forward inclinations respectively of 5 degrees, 10 degrees, and 15 degrees. With increasing forward inclination of the seat, the spine moved toward lumbar lordosis.”

Note: Lumbar lordosis is the natural curve of the lumbar spine explained as increased curving of the lumbar spine (which can become flattened when leaning forward while seated on a flat surface, called kyphosis).

Body’s Adaption to Seat Inclination

“A supplementary sample showed that 1/3 of the body’s adaptation to the seat inclination took place in the spine and 2/3 in the hip joints. A tendency to a more vertical position of the trunk as a whole was observed on the 5 degree chair but the posture of the cervical (neck) spine was not influenced by the seat inclination. . .a comfort evaluation showed the 5 degree forward inclination and the horizontal seats to be preferred.”

Previous Studies & Backwards Inclination

The above-mentioned study goes on to discuss the findings of previous studies: “Many investigators (Akerblom, B., 1948; Grandjean, E., 1975; Keegan, J., 1953; Ollefs, H., 1951; Schubert, H., 1962) recommend that the seat surface should be inclined about 5 degrees backwards; one has even suggested 15 degrees backwards, (Rizzi, M., 1969). Others suggest that the seat should be almost horizontal, (Kroemer, K. H. E., 1971; Peters, T., 1969); and in some committees (Comite Europeen de Normalisation, 1979; Engdahl, S., 1971; ISO: Draft International Standard ISO/DIS 5970), a range from 0 degrees to 4 to 5 degrees backwards had been suggested.”

Previous Studies & Forward Inclination

“Another body of opinion focuses on the possible advantages of a forward inclination of either the whole seat (Burandt, U., 1969; Drescher, E.W., 1929; Laurig, W., 1969; Mandal, A.C., 1970 and 1981; Schlegel, K.F., 1940; Staffel, F. 1884), the posterior part (Burandt, U. & Grandjean, E., 1964; Schneider, H.J., et al., 1961), or the anterior half, (Jurgens, H.W. 1969).”

Tiltable Inclination

“Mandal suggests a tiltable seat from -5 degrees (backwards) to +15 degrees (forward); and Kroemer (1971) suggests an adjustable seat slope between -6 degrees (backwards) and +6 degrees (forward), to make it possible to changes the position for different tasks.”

Purpose of Study

“The purposes of the above-mentioned study were:
1. “To compare spontaneously chosen posture when sitting for one hour on each of the four seat inclinations — horizontal, 5 degrees, 10 degrees, and 15 degrees forward — and to estimate the adaptability of the trunk and hip joints to different forward inclinations of the seat.
2. “To follow the changes of the spinal curves during one hour of sitting on one seat.
3. “To evaluate comfort in relation to the different seat inclinations.”

Tiltable Office Chair Furnished to Study Subjects

“To accustom the subjects to a forward-inclining seat, their homes were furnished with a tiltable office chair at least two weeks before the experiment. The seat could tilt from 5 degrees backwards to 15 degrees forwards . . . to ensure that the thighs conformed to the seat surface, height adjustment was effectuated by placing the seat at first a little too high, with the legs hanging freely, and later lowering it until the feet rested on the floor with the lower part of the legs vertical. Approximately 2/3 of the thighs were resting on the seat.

Preference for Horizontal & 5 Degree Inclination

“At the end of the period of sitting, all subjects were asked to estimate the degree of comfort on each specific seat inclination, using a scale from 1 (poor) to 5 (excellent.). The same scale was used to rate the tillable chair they had used for two weeks in their home. The comfort evaluation that was done in the above-mentioned study, “shows a preference for the 0 degree and the 5 degree inclinations.”

Study Evaluation of Tiltable Seat

“The corresponding comfort evaluation of the office chair with the tiltable seat, which the subjects had in their homes, was of the median 3.5 (5 execellent to 1 poor) (range 1-5).”

Increasing Inclination = Advantageous for Lordosis

“With increasing seat inclination forward, the spine changed towards lumbar lordosis. Almost all authors claim such a change as an advantage when sitting, (Akerblom, B., 1948; Burandt, U. & Grandjean, E., 1964; Jurgens, H.W., 169; Schlegel, K.F., 1940; Schneider, H.J. & Lippert, H., 1961; and Snorrason, E., 1955; Staffel, F., 1884).”

6 Hours Sitting May Cause Pressure Sore

SITTING & PRESSURE
By Darren Salinger, M.D., OB/GYN
& Melanie Loomos, Inventor

In modern society, sitting takes up an increasing amount of time, both at home and at work. It has been concluded there is a considerable shift to sedentary work in industrialized countries (3).

1881 Analysis of Contact Stresses

The original analysis of contact stresses which lead to pressure-related problems while sitting was published in 1881 by Heinrich Hertz (5).

6 Hours Sitting May Cause Pressure Sore

A healthy individual can develop a pressure sore in six to twelve hours if left undisturbed in the same position (7). A single pressure sore costs more than $8,000 to heal. The yearly costs of treating pressure sores and related problems have been estimated to be almost $1 billion (9).

One study found that 63 percent of patients who sat for an unlimited period of time developed pressure sores whereas only 7 percent of patients developed pressure sores who sat for maximum periods of two hours (1).

Limiting sitting time is only one starting point in preventing pressure sores. Other possibilities include appropriate posture and pressure-reducing seat cushions (1).

In a test of six pressure-relieving devices, the air doughnut was found to be the least effective in reducing inter-surface pressures. None of the devices tested eliminated the inter-surface pressures generated by sitting in one position (7).

To prevent tissue damage, people must be able to shift their weight or be assisted to alternate pressure points (7).

External Pressure = 1/2 Internal Pressure

Externally measured pressure under the butt bones is only one half of the internal pressure. Given the pressures that are prevalent, Staarink (1995) found it amazing that more people do not get pressure ulcers (1).

Risk Factors for Pressure Sores

Studies have implicated factors such as posture and posture changes, impact loading of tissue, elevated temperature and humidity, age, nutritional status, general health, activity level, body stature and shear stress in the development of pressure sores (4).

Shear Force & Pressure Sores

The interest in shear stems from the observation that shear increases the possibility of causing a pressure sore (6). In 1958, it was Reichel who started to focus attention on shear force, which is defined as a force parallel to a surface (2). It is important to reduce shear force as much as possible (6). Avoidance of shear force is as important as avoidance of direct pressure (8).

Snijders (1984) showed that the inclination and the position of a backrest as well as the angle of the seat surface influence the shear force on the seat (3). The proper combination of backrest and seat inclination can reduce shear forces on the seat and on the sitter.

In tests done on healthy young subjects, it was found that when little shear is accepted, a fixed inclination between seat and backrest should be chosen between 90 degrees and 95 degrees (3). When a person is sitting down, the weight of the body is distributed over the supporting surfaces. The distributed shear and pressure result in forces that act on four major body points:
▪ The Feet
▪ The Butt Bones
▪ The Top of the Hip Bones
▪ The Chest

Shear Stresses Reduced – 90N to 5N

In a study measuring shear stresses on wheelchairs, using healthy young subjects, different seat angles were tested. Previous measurements showed that a total shear force on the seat of a foldable wheelchair could become as high as 90N when the seat is horizontal (2). When the seat slant is 8 degrees forward, the shear force becomes smaller than 5N in healthy subjects (2). The assumption is made that if the unfavorable effect of shear stress can be measured in healthy, young subjects, the effect for the hospitalized geriatric and paraplegic population will be even worse (2).

Enveloping Cushion

The enveloping property of a seat cushion is a measure of its tendency to wrap around the object it supports. When the body adopts a sitting posture, the weight of the body is distributed over the supporting surfaces (3). A good enveloping cushion provides a large contact area and a uniform stress distribution (9).

Medium density foam results in the lowest shear stresses and compressive stresses tested. Soft foam results in the next lowest shear and compressive stresses because soft foam tends to “bottom out” and cause pressure from the surface below the foam.

Caution: Temperature Sensitive Foam

Researchers caution against materials in seat surfaces that react to body temperature because there is a risk of rising temperatures and increased humidity which can lead to pressure sores (1), as well as other pressure-related problems.

Researchers conclude that the use of armrests in the case of healthy persons has a very limited pressure-reducing effect but may help stabilize posture.

  1. Applied Nursing Research, Vol. 12, No. 3, August 1999, pp. 136-142, “Sitting Posture and Prevention of Pressure Ulcers,” written by Tom Defloor, MScN, N.N.; and Maria H.F. Grypdonck, Ph.D., RN, Nursing Sciences, University of Gent, Belgium.
  2.  Scandinavian Journal of Rehabilitation Medicine, 29: 131-136, 1997, “Shear Stress Measured on Beds and Wheelchairs,” written by R.H.M. Goossens, Ph.D.; C.J. Snijders, Ph.D., T.G. Holscher, Mac; W. Chr. Heerens, Ph.D.; and A. E. Holman, MSc.
  3.  Journal of Biomechanics, Vol. 28, No. 2, pp. 225-230, 1995, “Design Criteria for the Reduction of Shear Forces in Beds and Seats,” written by R.H.M. Goossens and C.J. Snijders, Erasmus University, Rotterdam, Faculty of Medicine, Department of Biomedical Physics and Technology, The Netherlands.
  4. Journal of Rehabilitation Research and Development, Vol. 29, No. 4, 1992, pp. 21 – 31, Department of Veterans Affairs, “Comparative Effects of Posture on Pressure and Shear at the Body-Seat Interface,” written by Douglas A. Hobson, Ph.D., School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, P.A. U.S.A.
  5.  Journal of Rehabilitation Research and Development, Vol. 27, No. 2, 1990, pp. 135 – 140, Department of Veterans Affairs, “Reduction of Sitting Pressures with Custom Contoured Cushions,” written by Stephen Sprigle, Ph.D.; Kao-Chi Chung, Ph.D.; Clifford E. Brubaker, Ph.D., University of Virginia, Rehabilitation Engineering Center, U.S.A.
  6.  Journal of Rehabilitation Research and Development, Vol. 27, No. 3, 1990, pp. 239 – 246, Department of Veterans Affairs, “Sitting Forces and Wheelchair Mechanics,” written by Paul Gilsdorf, B.S.; Robert Patterson, Ph.D.; Steven Fisher, M.D.; Nancy Appel, P.T., Department of Physical Medicine and Rehabilitation, University of Minnesota, U.S.A.
  7.  American Journal of Nursing, 1987, “Sitting Easy: How Six Pressure-Relieving Devices Stack up,” written by Robin Charges, RN, M.A., M.S.N.; and Bettie S. Jackson, RN, Ed.D., F.A.A.N., Montefiore Medical Center, N.Y., U.S.A.
  8.  Arch. Phys. Med. Rehabil., Vol. 60, July, 1979, “Shear vs. Pressure as Causative Factors in Skin Blood Flow Occlusion,” written by Leon Bennett, MAE; David Kavner, DEng; Bok K. Lee, M.D.; Frieda A. Trainor, Ph.D., Veterans Administration Prosthetic Center, N.Y., U.S.A.
  9.  J. Biomechanics, Vol. 15, No. 7, 1982, “Model Experiments to Study the Stress Distributions in a Seated Buttock,” Narender P. Reddy, Himanshu Patel, George Van B. Cochran, Biomechanics Research Unit, Helen Hayes Hospital; and John B. Brunski, Center for Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, N.Y., U.S.A.

OSHA watch — Premium Reduction Center Blog

Temporary enforcement policy on monorail hoists in construction Employers whose monorail hoists fail to comply with requirements in the Crane and Derricks in Construction Standard will not be issued citations as long as they adhere to other regulations, according to a recent memorandum. The temporary enforcement policy notes stakeholders identified gaps in the standard regarding […]

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Hemorrhoids, History & the Western World

Hemorrhoids

Hemorrhoids are one of the most frequent problems people in westernized countries face. There are estimates of up to 75 to 90 percent occurrence rates of hemorrhoids in the U.S. population (1, 2, 3, 4, 5). An estimated 50 percent of those over the age of 50 years require some type of conservative or operative therapy (4).

The cost to the community, both financial and in lost work days, is great; and by any standards, this condition must be considered a major health hazard (7).

Seating & Hemorrhoids

Preventative measures to reduce risk factors for the development of hemorrhoids should be taken before it is too late. It is important to minimize external compression from poorly designed seating as much as possible. External compression from poorly designed seating concentrates forces on small areas of the body. This results in high localized pressure. The pressure can compress nerves, vessels, and other soft tissues, resulting in tissue-specific damage. These changes may themselves result in disease or predispose other tissues to damage.

U.S. History & Hemorrhoids

Hemorrhoids have plagued men and women for centuries, inflicting pain equally on individuals at all levels of society and of all occupations: Emperors (Napoleon); U.S. Presidents (Jimmy Carter); baseball sluggers (George Brett); judges; policemen; truck and cab drivers; and jockeys (6).

Ancient History & Hemorrhoids

It has been said that Napoleon’s hemorrhoids were troubling him during the battle of Waterloo (7).

Proctology flourished as a specialty in Ancient Egypt. The surgical treatment of hemorrhoids was practiced in Ancient Greece, and Hippocrates suggested that the cause could be attributed to bile and phlegm (8).

The Western World vs. The Third World & Hemorrhoids

Today, hemorrhoids are considered to be one of the most common ills of men and women, a judgment made by those with vision limited to the Western World (7).

The high rate of hemorrhoids in westernized societies contrasts sharply with Third World countries. Only about one in 25 to one in 30 individuals is thought to have hemorrhoids as compared to one in two individuals in Westernized societies. One doctor recounted in 30 years’ practice in Africa, one of the only two patients he saw with severe hemorrhoids was a prince taking a semi-European diet (5, 7).

1) Primary Care, Volume 26, Number 1, March, 1999, “Hemorrhoids,” by Joy N. Hussain, M.D., Cairns Base Hospital, Australia.
2) Family Medicine Principles & Practices, 1998, Fifth Edition: Chapter 91, “Diseases of the Rectum and Anus,” by Thomas J. Zuber.
3) MJA, Vol. 167, July, 1997, Clinical Practice, “Hemorrhoids: A Clinical Update,” written by Adrian L. Polglase, M.S., FRACS, Clinical associate Professor and Colorectal Surgeon, Australia.
4) American Family Physician, September 1, 1995, “Non-surgical Treatment Options for Internal Hemorrhoids, written by John Pfenninger, M.D., and James Surrel, M.D.
5) Surgical Clinics of North America, Vol. 65, No. 6, December, 1988, “Hemorrhoids, Non-operative Management,” written by A. R. Dennison, M.D.; D.C., Wherry, M.D.; and D.L. Morris, M.D., Ph.D.
6) Southern Medical Journal, Vol. 81, No. 5, May, 1988, “Alternatives in the Treatment of Hemorrhoidal Disease,” by Emmet F. Ferguson, Jr., M.D., University of Florida, School of Medicine, Jacksonville, F.L., U.S.A.
7) Postgraduate Medical Journal, September, 1975, 51, 631-636, “Hemorrhoids – Postulated Pathogenesis and Proposed Prevention,” written by D. P. Burkitt, C.M.G., M.D., F.R.C.S., F.R.S., and C.W. Graham-Stewart, MS, F.R.C.S.
8) The American Journal of Proctology, Vol. 21, No. 3, June 1970, “An Epidemiological Investigation of Hemorrhoids, written by John Philpot, Ph.D., Rutgers, The State University, New Jersey, U.S.A.

Forward Bending & Low Back Pain

Spine, Volume 21, Number 1, pp. 71-78, 1996, “Analysis of Lumbar Spine and Hip Motion During Forward Bending in Subjects With and Without a History of Low Back Pain,” written by Marcia A. Esola, M.S., P.T.; Philip W. McClure, M.S., P.T.; G. Kelley Fitzgerald, M.S., P.T.; and Sorin Siegler, Ph.D., U.S.A.:

In this study, a motion analysis system was used to measure the amount and velocity of lumbar spine and hip motion during forward bending.

The authors begin by citing the following previous findings:

EPIDEMIC OF LOW BACK PAIN

“Disorders of the low back have reached epidemic proportions, (DeRosa, C.P., 1992).”

BILLIONS OF $$$ ANNUALLY, LOST WORK TIME & WORKERS’ COMP CLAIMS

“Epidemiologic studies show that billions of dollars are spent annually on the problem of low back pain, which is one of the most commonly-cited problems for lost work time in industry and Workers’ Compensation claims, (Chase, J.A., 1992; Frymoyer, J.W., 1988; and Pope, M.H., et al., 1991).”

FREQUENT FORWARD BENDING & LOW BACK PAIN

“Researchers have shown an association between frequent forward bending and low back pain, (Berquist-Ullman, M., et al., 1977; Magora, A., 1973; Mellin, G., 1986; Punnett, L, et al., 1991; Svensson H.O., et al., 1989; Videman T., et al., 1989).”

SLOUCHING WHILE SEATED / BENDING AT THE WAIST WHILE STANDING

“Prolonged sitting with the lumbar spine in a flexed position (slouching) and flexed standing postures (bending at the waist) are also associated with an increased risk of low back pain, (Anderson, G.B.J., 1991; Berquist-Ullman, M., et al., 1977; Magora, A., 1972; Punnett, L., et al., 1991; Riihimaki, H., et al., 1989).”

OCCUPATIONS INVOLVING REPETITIVE FORWARD BENDING

“Saunders reports that people with herniated inter-vertebral discs often have a history of an activity or occupation involving repetitive forward bending.”

“Nachemson (1981) has shown that inter-vertebral disc pressure increases 20 percent over that measured in standing when forward bending 20 degrees, and increases 100 percent when bending up to 40 degrees.”

INADEQUATE HIP FLEXIBILITY & EXCESSIVE LUMBAR MOTION

“It has been suggested that inadequate hip flexibility coupled with excessive lumbar motion during forward bending results in low back pain, (Biering-Sorenson, F., 1984; Sahramann, S.A., 1993). . .Sahramann (1993) suggests that excessive lumbar mobility leads to tissue overloading, micro-trauma, and ultimately the development of degenerative joint and disc disease. A person may experience low back pain at any stage of this sequence of events.

FORWARD BENDING = RISK FACTOR FOR LOW BACK PAIN

“Forward bending has been clearly recognized as a risk factor for low back pain. Altered movement patterns of the lumbar spine and hips during forward bending may help explain why forward bending is a risk factor for the development of low back pain.”

HAMSTRING STRETCHING HELPFUL 

In the conclusions, the authors state: “The results provide quantitative data to guide clinical assessment of forward bending motion.  Results also suggest that although people with a history of low back pain have amounts of lumbar spine and hip motion during forward bending similar to those of healthy subjects, the pattern of motion is different.  It may be desirable to teach patients with a history of low back pain to use more hip motion during early forward bending, and hamstring stretching may be helpful for encouraging earlier hip motion.”

OSHA Revised Whistleblower Complaint

Trade Release

Department of Labor, United States of America

U.S. Department of Labor
Occupational Safety and Health Administration
Office of Communications
Washington, D.C.
www.osha.gov

For Immediate Release
July 28, 2017
Contact: Office of Communications
Phone: 202-693-1999

OSHA revises its online whistleblower complaint form

WASHINGTON – The Occupational Safety and Health Administration recently revised its online whistleblower complaint form to help users file a complaint with the appropriate agency. The form provides workers with another option for submitting retaliation complaints to the U.S. Department of Labor’s OSHA.

The updated form guides individuals as they file a complaint through the process, providing essential questions at the beginning so they can better understand and exercise their rights under relevant laws. One significant improvement to the system includes pop-up boxes with information about various agencies for individuals who indicate that they have engaged in protected activity that may be addressed by an agency other than OSHA. The new form is available in English and Spanish.

“Workers who report unsafe conditions and wrongdoing have a range of legal protections from retaliation,” said Deputy Assistant Secretary of Labor for Occupational Safety and Health Loren Sweatt. “The revised online complaint form works to ensure whistleblowers file their complaints with the appropriate federal agency for prompt action.”

In addition to the online form, workers can file complaints by fax, mail, or hand-delivery; contacting the agency at 800-321-6742; or calling an OSHA regional or area office.

OSHA enforces the whistleblower provisions of 22 statutes protecting employees who report violations of various securities laws, trucking, airline, nuclear power, pipeline, environmental, rail, public transportation, workplace safety and health, and consumer protection laws. Detailed information on employee whistleblower rights, including fact sheets, is available online at http://www.whistleblowers.gov/.

Under the Occupational Safety and Health Act of 1970, employers are responsible for providing safe and healthful workplaces for their employees. OSHA’s role is to ensure these conditions for America’s working men and women by setting and enforcing standards, and providing training, education and assistance. For more information, visit www.osha.gov.

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OSHA Resources on Silica Final Rule

Information from OSHA

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U.S. Department of Labor

Occupational Safety and Health Administration

Office of Communications

202-693-1999

Department of Labor, United States of America

New and revised resources available from OSHA on silica final rule

OSHA has released two resources to help small business employers comply with the agency’s final silica rule. The Small Entity Compliance Guide for General Industry and Maritime outlines steps that employers are required to take including: assessing worker exposures; using engineering and work practice controls to keep exposures below a specified safety threshold; offering medical exams to certain highly exposed workers; and training workers. Enforcement of the final rule is scheduled to begin June 23, 2018.

Released earlier in the year, the Small Entity Compliance Guide for Construction describes requirements to protect employees including: using engineering controls specified in the standard or selecting other effective engineering controls to reduce exposures; offering medical exams to workers who will need to wear a respirator under the silica standard for 30 or more days a year; and training workers. The guide was updated to reflect the new enforcement date of Sept. 23, 2017.

You are receiving this email because you signed up for updates on the agency’s silica rule. To unsubscribe, see below.