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An Ergonomic “Rec”

During the COVID lockdown and the recent preponderance of working from home, some companies and organizations are offering incentives and financial recompense for employees to improve their at home working environment. This is a similar program to those that encourage healthy employee habits by incentivizing sports equipment and gym memberships. Keeping people apart during this pandemic is important and helpful in lowering the infection rate. One such pair of people, living together in a small apartment in San Francisco have the opportunity to benefit from a program offered by their employers. They are currently working from home as computer science engineers and have been noticing irksome ergonomic issues by their newly discovered posture while using their laptops. The female subject, named Maya for purposes of this project, typically uses her laptop on a table who’s original purpose may or may not have been a desk. It is a wide surface, supported by legs on wheels. None of the chairs she uses for this task are the right height for her. She will commonly migrate to the dining table, or the couch in order to change positions in search for comfort. The male subject, referred to as Gregory, rarely uses the table/desk surface, but more often relies solely on the dining table as a workspace, or like Maya, resorts to the couch, or even the bed for a change in posture. Maya has vocalized complaints of numbness in her legs as well as soreness and pain in her lower back. Gregory echoes similar discomfort. They are both active, healthy individuals in their early forties and are seeking an ergonomic improvement in their working from home lifestyle. They are also both avid bicyclists who proudly store their bicycles in this same living room of their small apartment. This paper and associated project aims to offer a design and ergonomic solution that may not only minimize or eliminate their laptop use discomfort, but also develop an aesthetically pleasing storage [display] solution for their bicycles by assessing their individual anthropometric geometries, compared to industry standards, and larger sample population; analysis of their space; and incorporate strategies from Norman’s Design of Everyday Things, Bridger’s Introduction to Ergonomics in creating an ergonomic and visually pleasing design.

Attempting to quantify their posture proved difficult with the pandemic lockdown of course, so effort was made to limit the timeframe of contact. A REBA assessment was performed of both Gregory and Maya in a number of their common working locations in their apartment. A REBA assessment is an analysis of the entire body posture for risk of WRMSD’s, or Work Related Musculoskeletal Disorders. REBA is an acronym that stands for Rapid Entire Body Assessment, developed by Sue Hignett and Lynn McAtamney. This is a tool for employers to conduct ergonomic surveys of employee tasks commonly utilized by industrial and commercial organizations (i.e., commercial laundry, automotive detailers, etc). While seated laptop use isn’t perhaps the most applicable task for the REBA analysis, it does still yield some telling data. The REBA assessment factors analysis of the body’s neck, abdomen, and leg positions, as well as any extremes these body parts are put into for any duration of time or additional force and load. The second half of the assessment considers the wrist, upper and lower arm positions within a specific task as well as activities and grip functions.

After performing six or so assessments, I became comfortable explaining to the subjects how some of these aspects figured into their work. Specifically how the “Activity Score” in Step 13 was considered, subjectively working with a laptop one can gauge that one or more body parts will be held for a minute or longer, this could be deemed “static” work. For leg positioning I estimated it to be in the +1 range, relaxed in a sense; taking also from the example in Bridger’s Ergonomic Workshop 4.1: legs scored a 1 as well with the note, “person is sitting”. Repeated small range actions (guiding a mouse, or track pad for example) would also score a 1. I defined the final activity score as being sudden movements or reactions that cause “rapid large range changes in posture or unstable base”—seated working on a laptop would not qualify. By comparison, I assessed my own work activity as a career bicycle mechanic and scored myself a REBA score of 15. Standing for hours at a time, reaching and twisting, applying heavy loads with tools, seeing this difference was enlightening. Performing the assessment with these two individuals provided the following scores:

 dining tabledeskcouchmechanic
Step 1: Neck Position1124
Step 2: Trunk Position2125
Step 3: Legs1133
Step 4: Posture Score A2159
Step 5: Force/Load0002
Step 6: SCORE A21511
Step 7: Upper Arm Position2115
Step 8: Lower Arm Position2222
Step 9: Wrist Position1222
Step 10: Posture Score B2228
Step 11: Coupling Score0001
Step 12: SCORE B2229
Step 13: Activity Score2223
REBA Score43615
Table 1.1: REBA scores for at home work station positions, as well as example of bicycle mechanic for comparative value
Image 1.1: One of the REBA Assessment forms filled out showing the postural analysis of the subject using a laptop while seated on their couch, scoring in the “Medium Risk” category

As the scoring system of the REBA worksheet states, these scores yield a range of risks, from the desk posture being Low Risk, “Change may be needed” to the dining table and couch spanning the Medium Risk range with the advice of “Further investigation. Change soon.” And a bicycle mechanic at the top: Very High Risk “Implement change”.

As Bridger also states, the results of a REBA analysis should be “interpreted together with data on real injury rates….” Given the above listed results, Maya, who primarily works at a desk, while being the lowest risk, however claims symptoms of lower back pain, numbness in her legs as stated, as well as discomfort in her wrists. See image 1.1, a photo of her seated at her desk demonstrates some logic to these injuries and discomforts. Her neck is within the 10-20 ̊ range, no bending or twisting, her trunk is very close to straight. Where she scores aberrantly is barely noticeable at the wrists and lower arm positions. The photo in Image 1.2 is slightly misleading as it was taken after the subject placed a thick book on the seat to raise herself; an augmentation she performs frequently she states. This observation and assessment gives confirmation to her complaints. The discomfort in her wrists can be attributable to the 15 ̊ or more incline her lower arms and wrists need to make in order for her to reach her keyboard. Without the aid of the book under her buttocks, Maya begins to feel an impingement on the underside of her thighs from the seat she typically uses (shown), over time this contributes to the numbness in her lower legs. Even with the book there is additional but different impingement that only exacerbates the numbness. This is certainly an anthropometric mismatch as

Image 1.2: While it may appear that the subject Maya has neutral posture at her desk, take note of the thick book she is sitting on.
Photo MW.

emphasized by Bridger in chapter 4, this combination of improper seating, augmented seating (with book), are increasing “the postural load on” Maya’s body. He goes on specifically, “short users may have to raise seat heights beyond popliteal height to gain access to the desk.” As her feet don’t fully contact the ground sufficiently, her legs are restricting blood flow, causing the numbness. She is also unable to stabilize her weight causing her to do so with her abdomen which may be contributing to her sore back muscles.

In an effort to find a solution for Maya and Gregory’s ergonomic challenges I approached the problem with the intention of gathering as much data as I was able to better quantify my findings. Following a select set of measurements from Human Dimension and Interior Space, I sought to build an anthropometric picture of these two subjects. These listings (in Table 1.2) each quantified a variable that might contribute to positioning their posture in a more ideal way:

 GregoryMaya
Age4242
Stature 1A7164
Eye Height (Standing) 1B6860.5
Sitting Height (Erect) 1D33.534
Eye Height (Sitting) 1F28.531
Elbow Height Resting 1K10.510
Thigh Clearance 1L5.55
Knee Height 1M2220
Popliteal Height 1N18.517
Buttock-Popliteal Height 1O1816.5
Buttock-Knee Height 1P21.519
Vertical Reach (Sitting) 1S47.547
Vertical Reach (Standing) 1T80.578
Table 1.2: HDIS anthropometric measurements, as well as age, of the subjects

Arming myself with other resources such as the averages developed by Henry Dreyfuss and the Humanscale sliders, I compiled some other metrics on Table 1.3, comparing these to the measured anthropometrics of the subjects shows an evident difference and deviation from the general. This is most noticeable in the Eye to Seat Height of 32.3 below compared to the 28.3” measured on Gregory for example.

 GregoryMaya
HumanScale Readings based on Stature  
Easy High Reach78.971.4
Standing Elbow Height43.438.9
Leg Room Seated18.516.3
Compressed Seat Height17.515.7
Max Seat Length19.417.3
Eye to Seat32.329.2
Lumbar Height109.3
Table 1.3: Select Humanscale measurements based on average stature
Image 1.3: Humanscale Body Measurements for standing heights of 64” and 71”

Other aspects of this couple’s work from home office is what could best be described as a lack of any clear-cut office space. This is perhaps a sudden problem for many people in this state of pandemic lockdown, it is one that may or may not need to be resolved. People are now being tasked with working their jobs in an environment not necessarily suited to do so—this is certainly the case with the population that doesn’t work an office/desk job—this type of work is arguably easier to implement in the home environment better than employment as a bicycle mechanic or retail customer service as an example, however, it may be helpful for this couple to designate a work space to act as a signifier per se as to where their work from home office space should be. This not only defines the space, but also helps define when not to be working. Productivity for some people is improved if the proper mental state is achieved by stimulating familiar activities or work spaces. I have heard many stories of people getting in their car to “commute” around the block before commencing their work from home in order to kickstart their productivity. Perhaps a stretch, but this may act as a signifier and constraint in the vein of Don Norman’s Design of Everyday Things.

As the space is currently, there is only the significance of relaxation and bicycle storage in terms of areas of activity as depicted in Image 1.4 below. Their initial interest has been to find a solution to amend their ergonomic woes incorporated into this wall behind the aforementioned couch.

Image 1.4: The mid-century modern couch, cubic coffee tables, and two bicycles
Photo MW

Their current dining table sits at a height of 29” which is within the standard range of 28 – 30,” which leaves room for the legs of most adults allowing their feet to contact the floor. The desk/table that Maya commonly uses is approximately the same height. They have a several dining and side chairs of varying heights as well as a “community” bench at their dining table that is sometimes used to sit on while working. Their couch seating surface only measures 16” from the floor, while the cubic coffee tables are 17.5” tall. According to the Humanscale measurements, and Maya’s stature of 64” the maximum table height is 26.9” while Gregory’s (at 71”) tops out at 30.2”.

But where else can we determine optimal measurements, we have a population of two individuals with a considerable stature difference. Gregory is 7” taller than Maya. Comparing their statures to their popliteal heights shows a fairly close ratio:

StaturePopliteal HeightRatio
7118.50.2606
64170.2656

Despite their seven inch difference, they do show an approximate sitting height similarity; this could be attributable to a short or longer proportionate torso length, as well as a potential slouching despite the attempt to measure an erect, upright sitting posture. Other comparisons between the subjects demonstrate a similar proportions to their stature:

StatureElbow HeightRatio
7110.50.1479
64100.1563
 Sitting HeightRatio
7133.50.4718
64340.5313
 Eye Height StandingRatio
71680.9577
6460.50.9453

Calculating a workspace redesign for Maya and Gregory based solely on these numbers would be akin to a custom designed product given the minimal spread of data across merely two subjects. Considering the potential for other people using this workspace a wider population would need to be factored in. Using metrics collected from my household, as well as volunteers from class, I am able to capture a wider swath of potential users.

Out of this population, in terms of stature, Gregory is in the 89th percentile compared to Maya’s 40th. The average stature of the population is 66.51” tall. Other key metrics include the following percentiles:

 StatureElbow HeightPopliteal HeightSitting HeightEye Height Standing
Gregory89th94th76th38th85th
Maya40th85th41st47th26th
Table 1.4: The subject’s percentiles for select metrics based on the wider population

These percentiles were calculated using the standard deviation of 4.41 for stature, .96 for elbow height, 1.61 for popliteal height, 2.0 with sitting height, and 4.47 for standing eye height. The wider population has an average elbow height of 9”, an average popliteal height of 17.56,” an average sitting height of 34.25,” and a standing eye height of 63.30”. These specific metric categories were selected from a basis of measurements that would directly affect posture, comfort, and ergonomic solutions as well as which categories I was able to collect samples from.

Taking the population into consideration for a solution, adjustability would be ideal, this would involve an adjustable height chair to accommodate the spreads of popliteal height of the population

So, taking the lowest percentile for elbow height out of the wider population of 8 inches coupled with the popliteal height (plus thigh height) demonstrates that the lowest a desk top surface should be is 26 inches (assuming a minimum two inches desktop thickness). This is also factoring in the chair seat height being accommodating to the 8th percentile group from this population (with a popliteal height of 14.5”). The upper percentiles would likely find this too low for them, as Gregory would no doubt discover that while his 18.5” popliteal height would put his knees a little higher than comfortable from the low seat, the height of the desk would possibly be too low and would begin to feel strain in his arms from their lack of support from the desk top. According to Bridger, “much office furniture is designed around a desk height of ~73cm” or 28.74”.

The solution for accommodating both Maya, Gregory, and the current population of this class would most likely involve an adjustable height desk chair; a range of heights would be captured within these adjustments. Something that would feature a height adjustment of the seat position primarily. Including further adjustments in arm rest height and position would be a bonus to further prevent the arms from having to support themselves. As stated in Bridger’s Introduction to Ergonomics (and the inference of extreme angles gaining negative scores on the REBA assessment) a neutral work posture is ideal. Maintaining a supported wrist and forearm implies that the joint range is being kept in a neutral position: by supporting the weight of the arms, “less load is placed on the lumbar spine”. Bridger elaborates on this point specifically when discussing “mouse-intensive tasks” as characterized by “static, non-neutral postures of the wrist and shoulder”. 

Image 1.5: Two adjustable height chair options from Herman Miller, the Aeron and Sayl models. Both feature adjustable arm rests for supporting the forearm and elbow. 
Photos from hermanmiller.com

Herman Miller Aeron or Sayl chairs for example features height adjustment from 15 inches to 19” (this model actually has a variety of sizes that have different ranges of height adjustment as well). These are both fantastic examples of a well designed, fully accommodating office chairs. Even the Aeron website product sheet states it is made for a population range of 1st to 99th percentile. Coupled with an adjustable height desk surface would enable most users to work with a comfortable, injury and fatigue-free posture. Standing desks as they are called have a height adjustment range of 25 to 50 inches. With this 66% difference in desk height, and the 23% difference in seat height range, this combination would be fully accommodative to Gregory and Maya as well as the general adult population. The additional ability to completely forgo the chair and work while standing is another option with utilizing a standing desk. Also noted in Introduction to Ergonomics, Bridger points out that, “jobs that impose a high degree of postural constraint” are ones that “require maximum flexibility” and introducing adjustable furniture is one way to compensate for that constraint. Allowing Gregory and Maya to change their working posture throughout their working day would contribute to that flexibility by giving them the opportunity to stand and sit as they deem necessary to achieve their preferred postural strategy. Providing this kind of flexibility would allow a wide array of individuals of varying anthropometric measurements utilize this workspace. Considering the desk will primarily be used for a laptop, having the ability to raise the screen to a more ergonomically beneficial position. Again, pulling from Bridger’s Introduction to Ergonomics, screen height affects posture with findings stating that a low sight line angle was the most comfortable and most quality performing. This flexibility also contributes to a less sedentary lifestyle, moving around, alternating postures (from sitting to standing) helps prevent “the formation of blood clots deep in the legs” as claimed by the Harvard Business Review (Skerrett, Patrick J. The Many Benefits of Standing at Your Desk, https://hbr.org/2010/08/the-many-benefits-of-standing.htmlAugust 30, 2010). This detriment is echoed by Bridger when discussing health hazards like restricted blood flow.

Image 1.6: The ability to alternate working posture while at a desk can minimize musculoskeletal discomforts.
Photo from linak-us.com

Regarding other aspects to this workspace, lighting may be an issue needing investigation. Short of conducting a strategic lighting study to determine the lux value on this desk arrangement (which might be sufficiently achieved with a simple light meter app on the smartphone of which many free versions are available), it would be worth discussing the lights currently in use. The only lights at the moment are two ceiling mounted recessed canister lights and a large paper diffused chandelier above the dining table. There is ambient light from a frosted window adjacent to the proposed wall, as well as a large sliding glass western facing window directly opposite, about 15 feet across the living room space. Efforts would need to be made to manage the amount of glare received from the overhead lighting either by augmenting them with some type of deflection or perhaps, less unsightly, replacing the bulbs with a style that offers adjustable color temperatures and dimmability to better manage productivity (by selecting a dependent on the activity). This would possibly trade the aspect of glare for the benefit of better mental focus or a relaxed mind depending on the need. Having the lights set at a high color temperature (500k +) evidently produces a cool white light that tends to “assist with focus and attention” desirable while concentrating on work, while a warm white in the 2700k range delivers a relaxing atmosphere. (Duncan, Jason. Benefits of Color-Changing LED Lighting, https://www.energylightingservices.com/3171-2/ Jan 17, 2019). Any undue reflectance from the western-facing window could be ameliorated by drawing the curtains at those late afternoon hours. Maya’s interest in painting this wall may be opportune, currently the white wall may be providing the too much contrast to her laptop; depending on the tasks she typically conducts on the screen, a calculated color could be chosen to optimize this contrast in order to allow the “surface luminances” to gradually diminish to the surroundings as advised by Bridger.

Specific to Maya and Gregory’s work place at home, the most optimal location for this addition of a desk would be the same wall that they proudly display (and store) their primary means of exercise and transportation, their bicycles. In an effort to combine this workspace redesign, and relocating the bicycles being impossible, repositioning the bicycles is the next best idea. Utilizing the verticality of the wall, the bicycles can be stored hanging by their rear wheel in a vertical orientation. With the bicycle oriented this way, it minimizes how much it protrudes into the circulation of the room (between the wall, desk, and living room furniture) thus acting as a constraint of sorts—with the bicycle elevated this way in the sightline individuals walking will be less prone to bumping into the bicycle as they have the potential now to be literally overlooked. (This line of sight would also accentuate the bicycle frame precisely as an art piece). Another feature that could be designed in this system would also be to minimize the desk’s footprint on the floor, but incorporating the motors into the actual wall. As this couple will only be using laptops 

Instead of a simple hook on the wall, the rack itself might be designed decoratively or stylishly enough that even without a bicycle mounted on it, it would be aesthetically pleasing. This vertically mounted bike rack incidentally could afford the ability to hold other things as well, an ad hoc coat rack perhaps even. This system would feature a groove that would further constrain the bicycle to a position of laying flat against the wall.

The conceptual model of the workspace and the relaxation space, designated in order to enable a distinct break between work-life and home-life—this separation may become blurred if an external monitor is introduced. This workspace and display/storage redesign would feature numerous other fundamental principles of interaction such as the control for the standing desk, a lot of these systems are designed with a control pad that allows a programming of preferred heights. The raise/lower buttons are commonly mapped in an obvious method, with the sequence of programmed positions laid out as demonstrated in Image 1.7. As the height needs adjustment, the user merely needs to press and hold the raise/lower button until the desired height is achieved. The programmed positions provide the feedback of stopping at their pre-determined heights. Further feedback is given when the system recognizes a button is pressed by illuminating itself as well as providing a LCD measurement display.

Image 1.7: Standing desk control panel providing visual feedback. Photo MW

This desk system’s intention of alleviating a user’s ergonomic discomfort would function by the user accepting and understanding the initial conceptual model of the desk as a workspace. For Gregory and Maya, this is fundamental knowledge in their heads, the workspace confirms this as being the knowledge in the world. Opening their laptop and commencing their work tasks (attempting to achieve their goal of being productive), performing their coding, writing, or designing tasks is executed as expected. As their work day progresses, as the minutes tick by Maya gradually begins feeling a discomfort in her wrists, or her back, perceiving and interpreting this discomfort, for example with her new standing desk, now has the ability to change her working posture by changing the height of her desk. This enables her to continue being productive without expected aches and pains. In likely a short period of time, these adjustments will become almost a subconscious activity. This process could potentially become even more subconscious through an automation in the desk raising. For instance, after a predetermined time period, programmed by the users, the desk could provide a signal that would recommend Gregory or Maya to change positions, avoiding the tendency to remain in an uncomfortable or potentially injurious posture. One element to some of these control boards that may be lacking is a tactile feedback, a smooth and flat surface appears nicely designed, but including a raised ridge on each button would be helpful in activating them quicker.

Regarding the user interaction with the bicycle racks, again, the knowledge of their purpose would exist in Gregory and Maya’s heads. But what about potentially new tenants to this apartment that may not receive a direct walk-through from “those in the know”. How would they learn what these artistic, perhaps oddly spaced for, coat-racks? Some type of ornament could be included in the aesthetic design to signify their purpose would be a solution. A subtle, embossed image of a bicycle perhaps—aesthetically placed “knowledge in the world”. 

The actual shape of the bicycle hanging system could be a vertical member that would extend from the wall a couple inches at most, from this an arm would protrude from the upper portion and this would feature a groove that the user’s bicycle wheel would rest in, supporting the weight of the bicycle hanging below. This groove would be a modular component to allow a user to switch out depending on the width of their bicycle’s wheel. (There could be numerous versions of this component available for customizing the system in a multitude of ways even by each having a different angle even to accommodate different shape and sizes of handlebars). Along the vertical member mounted to the wall, should include another, lower protruding arm to stabilize the bicycle as it hangs to constrain it from swinging. Further constraints might be designed to prevent a user from accidentally “missing” the groove and dropping the bicycle. This would be akin to Norman’s forcing function: “the actions constrained so that failure [the bicycle not being secure in the groove] prevents the next step from happening [walking away after hanging the bicycle]” (Norman, Don. The Design of Everyday Things. Basic Books, 2013). How to constrain a user from walking away without securing the frame to the lower stabilizing support will require further creativity.

Image 1.8: Conceptual sketch of bicycle storage hook system. Design MW

In summary, if Maya and Gregory were to use their casual and dining chairs for their intended purpose and invest in a height adjustable desk and office chair, their anthropometric mismatched issues would be remedied. Given the limited dimensions of their apartment, the most suitable solution would be to utilize the wall they are currently using as their bicycle storage location, appealing to their love of bicycles, minimizing the footprint of the bicycles by hanging them on the wall would allow for greater ease of circulation, as well as indirectly demarcate the workspace from the living/relaxation spaces. Further minimizing the footprint of the workspace as to limit “work-time” encroachment on their “home-time” creating a custom standing desk with limited depth would further maximize their “home-space”.

Image 1.9: Conceptual sketch of wall re-design showing internally mounted standing desk, book shelves, and bicycle storage hanging positions. Design MW
Table 1.9: Layout of calculations and sample data

References

Books:

Norman, Don. The Design of Everyday Things. Basic Books, 2013

Bridger, R.S. Introduction to Ergonomics, Third Edition. CRC Press, 2009.

Diffrient, Tilley, Bardagjy. Humanscale 1/2/3 Manual. IA Collaborative Ventures LLC, 2017/1974

Panero & Zelnik Human Dimension & Interior Space. Whitney Library of Design, 1979

Sue Hignett􏰎, Lynn McAtamney􏰏. Technical Note, Rapid Entire Body Assessment (REBA), Applied Ergonomics 31, 2000 

Websites:

cnbc.com

physio-pedia.com

ergo-plus.com

forbes.com

hermanmiller.com

hermanmiller.com

linak-us.com

Skerrett, Patrick J. The Many Benefits of Standing at Your Desk. hbr.org

Duncan, Jason, Benefits of Color-Changing LED Lighting. energylightingservices.com