10 Things to Consider When Buying Multi-angle 4D Armrests mesh chair
Oct. 07, 2024
Office Chair with Arms: 2D, 3D & 4D Armrests Explained
How to Choose the Right Office Chair with Arms (2D, 3D and 4D Armrests Explained)
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If you're thinking of buying an office chair with arms, this short buyer's guide will show you some of the different height adjustable armrest options available and the different types of functionality they offer:
Height adjustable arm rest
A standard height adjustable arm rest will normally offer around 100mm of vertical adjustment.The height of the arm rest should be adjusted until it supports the weight of your arm at a 90 degree angle without hunching the shoulder (which would suggest the arm rest is too high). Ideally the arm rest should be level with your desk height too, allowing your forearm to be fully supported whilst typing or using a mouse.
Adjustments:
- 100mm vertical adjustment
2D Arm rest (Ideal for typing)
A 2D armrest will offer 100mm of vertical height adjustment but can also rotate inwards or outwards which is especially useful if you spend a lot of time typing. When we examine the rested position of our arms on a keyboard, we can see that they take on a triangular stance, so being able to invert the armrests ensures the forearms are fully supported whilst typing. This reduces strain on your wrists and prevents the weight of your arms pulling you forward into a slouch which is bad for your back.
2D Arm Adjustments:
- 100mm vertical adjustment
- 30 degree rotation (inwards or outwards)
3D Arm Rests
The 3D height adjustable armrest adds an additional feature over the 2D variant by allowing the armrest depth to be adjusted backwards or forwards by around 50mm. If the height of the armrest is set up correctly, your arms should be bent at around 90 - 110 degrees depending on what feels comfortable to you. Adjust the depth of the armrest accordingly. The 3D armrest type can also be moved backwards if you need to move your office chair closer to your desk.
3D Arm Adjustments:
- 100mm vertical adjustment
- 30 degree rotation (inwards or outwards)
- 50mm backwards and forwards
4D Arm Rests
The 4D armrest builds on the functionality of the 3D arm type by allowing around 25mm of horizontal (left to right) adjustment on each arm. This can be a particularly helpful feature if you have a larger build as you can free up an additional 50mm of space for your body and also ensure your arms are correctly positioned and well supported whilst in their rested position.
4D Arm Adjustments:
- 100mm vertical adjustment
- 30 degree rotation (inwards or outwards)
- 50mm backwards and forwards
- 25mm left to right
Conclusion
Choosing the right office chair with adjustable arms comes down personal preference and depends largely on the type of work you do. We hope this guide has been helpful but as always if you require any further advice, our friendly team are on hand to answer any questions you may have.
How to buy a good ergonomic office chair - Hope This Helps
How important is your chair?
Reading marketing materials for high-end office chairs can leave you with the belief that the ingenious, scientifically researched solutions used in their products guarantee a healthy spine. However, I have yet to meet a physical therapist or orthopedic surgeon who would place a great emphasis on chairs, let alone advise spending $1,000 on an upmarket chair. Professional recommendations for patients who have (or want to prevent) back problems are quite different, and generally focus on three things: sitting less, moving more and avoiding things that overload your spine. It is therefore safe to assume that replacing your average $100 office chair with a $1,000 ergonomic model will only be a small piece of the back health puzzle perhaps no more than 10 percent of the whole. This is why I wrote an entire FAQ on preventing back problems. You should probably read it if youre a computer worker and youre worried about the remaining mileage you can get out of your back.
Rule Number One
Never buy a chair without trying it out first in your own workspace. I cannot stress this enough. The worst thing you can do is read a bunch of Amazon reviews and buy the chair that got the highest average rating, or the chair that all your friends are raving about. People have wildly differing bodies, working habits and preferences. I was made aware of this fact during a chair-testing marathon that I did together with two of my friends (B and P), who were also in the market for new office chairs:
- B and I loved the Steelcase Leap, while P immediately eliminated it because of the sticky backrest that doesnt provide enough support as you lean forward.
- I found the Steelcase Please very comfortable, but I didnt like the armrests; to B, it felt about as comfortable as a wooden plank, but he didnt mind the armrests (which he doesnt use anyway).
- P and I both loved the Steelcase Think, while B found that the plastic strings in the backrest dug into his back.
The second worst thing you can do is to buy a chair after testing in the store for 30 minutes, with no possibility of returning it. There are a number of reasons why its a bad idea:
- An in-store test wont expose certain issues. You wont find out that the armrests keep bumping against your desk because they dont retract far enough. You wont notice that the seat gets uncomfortably hot after 1 hour of sitting. You wont pay attention to that slightly sticky knob. Issues like that can really ruin your long-term experience.
- An in-store test can also make you reject a chair prematurely. For example, if youre testing a chair that feels harder than your current chair, it will initially seem uncomfortable, perhaps unacceptably so. But that impression can vanish after a day or two of sitting in the chair.
- I dont know about you, but I dont like having the salesman over my shoulder.
The solution is to order from a vendor with a good return policy, or from a store that will allow you to test chairs for a few days before buying. In the office furniture business, companies frequently test-drive chairs in their own offices before they make a purchase if youre an individual, you just have to convince your local dealer to extend the same practice to you.
The virtues of changing your position
It is important to change your sitting position frequently. This allows you to spread the load among different sections of your spine, giving each section sufficient time to regenerate. At a minimum, your chair should enable easy switching between two positions:
- the near-upright position
- the reclined position
The reclined position is a great way to take some load off your lumbar spine, which is the part of the spine that is the source of the vast majority of back pain episodes. Instead of having your spine bear the entire weight of your head and torso, youre letting the backrest take some of the load. In addition, as you recline, youre restoring the natural curvature of your lumbar spine. (See more discussion of the mechanics.)
Unfortunately, reclining also makes your neck muscles work harder to keep your head from dropping backwards. In addition, if you want to keep your gaze at screen level, you have to flex your cervical spine and stretch the muscles in the back of the neck. Finally, it is harder to type in this position. For these reasons, the reclined position is best used for short periods (say, less than 20 minutes) when youre not typing a lot for instance, when youre thinking about what to write next, casually browsing the Web, or watching a short video. Your trunk in the reclined position should be at around 130°.
A headrest allows you to maintain the reclined position longer, but in my experience, the depth of the headrest has to be adjusted very precisely. Otherwise, your head will either drop too far back or stick forward either situation results in a sore neck. Unfortunately, chairs with good, highly adjustable headrests are few and far between. Furthermore, although a good headrest will take some (but not all) load off your muscles, it wont change the fact that your cervical spine is constantly flexed (so you can see the screen), putting pressure on your intervertebral discs and stretching the muscles that straighten your neck.
The near-upright position is much easier on your neck at the expense of your lumbar spine. Your trunk should be somewhere between 100° and 120° I personally prefer to get closer to 120°. Of course, you can and should continually change this angle if your chair allows it. Wider angles transfer more stress from the lumbar region to your neck.
Types of recline mechanisms
Before we go any further, I should explain some terms that I will be using in this post. There are two major types of recline mechanisms in task chairs:
- Smooth. This is the type you are probably most familiar with. It is found in your average low-end chair, as well as most high-end ones not made by Steelcase. If you put a little more weight on the backrest, it will recline. The further you recline, the more the backrest will resist your weight, which sets a soft limit on how far you can go. (Depending on the chair, resistance can rise slowly or quickly if it rises slowly, you can recline further, but you also feel less stable.)
- Sticky. This is used in most Steelcase chairs. With the smooth mechanism described above, the backrest reacts to your every movement just putting your arms forward will often result in it tilting forward. With the sticky mechanism, the experience is quite different. As you push back, the backrest does not immediately recline instead, it stays in place, as if it were a little stuck, until you apply enough force to overcome the static friction. Once it starts moving, you can easily put it at any angle you wish, as the backrest does not respond with increasing force the resistance is practically the same across the whole range of motion, allowing you to put the back in any position you wish. In this sort of chair, what keeps you from dropping all the way back is not the spring-like resistance its the static friction.
Here is a clip demonstrating a smooth mechanism on a Sedus Open Up chair. Notice that the backrest remains glued to my back, responding to my every move. Just bringing my arms closer to my body is enough to shift the balance and increase the recline angle. When I put my hands behind my head, my center of gravity shifts even more, resulting in a very large recline. The range of movement is limited by the increasing counterforce of the backrest I cannot maintain a large recline without putting my arms behind me. To do so, I would have to use my muscles (until they got tired) or change the tension setting (which is a bit of a hassle).
And heres a clip showing the sticky mechanism on the Steelcase Leap. Notice that small movements are ignored. When I move my arms around, the backrest flexes a bit, but the recline angle stays the same, held in place by static friction. In order to change the angle, I would have to do overcome the initial friction with my abdominal or back muscles. Once I do this initial work, my range of motion is unlimited. I can take any position (no matter how reclined) and maintain it without effort.
Recline mechanisms can also be classified along another dimension, which is independent of the smoothsticky dimension:
- Backrests with a tension control. The chair has a knob that lets you adjust the resistance of the backrest according to your weight and your preferred recline angle, with heavier users requiring more resistance. This is by far the most common type.
- Backrests with a weight mechanism. The resistance is automatically determined by your weight (the seat is connected to the recline mechanism). The idea is that users of different weights can sit on the chair, and the chair will automatically adjust the backrest resistance, so that they can all sit in roughly the same optimal position. This is especially handy in work environments in which one chair gets used by many different people. Example chairs that use this type of mechanism are the Humanscale Liberty and the Steelcase Think.
Easy changing between at least two positions
For reasons explained two sections earlier, you need a chair that, at a minimum, enables you to easily switch between two positions: the near-upright position and the reclined position. Of course, to do that, a chair must offer a properly reclined position (around 130°) in the first place.
Generally speaking, smooth backrests have difficulty with easy position switching. If you set the backrest for the near-upright position, then you cannot recline very far. The reason is that the resistance will go up quickly. You can use your muscles to force a reclined position, but this takes a lot of work and is impossible to maintain for any significant amount of time. You can make it a bit easier by putting your hands behind you, but then you cannot operate the keyboard and mouse, so the reclined position ends up being limited to passive activities like movie-watching.
The proper way to recline would be to turn the tension knob and lower the backrest resistance. Now you can recline easily, but youve traded away the near-upright position! If you try to sit upright, you will find that the backrest does not provide adequate support, so you have to use your abs or you drop back. Exaggerating a little, a smooth backrest mechanism only offers one position for a given resistance setting. Of course, the backrest is highly mobile and you can rock back and forth around some center point just not very far and not for very long.
In the case of smooth chairs with a weight mechanism instead of adjustable resistance, your options are even more limited. On a standard chair, you can at least change your position by turning the tension control knob with a weight mechanism, your position is determined by your weight. The chairs designers picked a recline angle that they considered optimal, and the weight mechanism is supposed to ensure that every user sits at this angle, regardless of their body weight. If an adjustable-tension chair only allows one position for any given resistance setting, a chair with weight-based resistance only allows one position the one selected by the chairs designer. There are exceptions to this rule for instance, the Steelcase Think chair has a weight mechanism with an additional, easy-to-reach knob that lets you choose between weight-based resistance and weight +20%, thus satisfying the requirement of enabling easy position changes (though not without some mechanical shortcomings).
Lets go back to chairs with adjustable resistance. As I mentioned above, you can switch between a near-upright position and a reclined position by turning the resistance knob. However, this doesnt work in practice, because tension controls on chairs are continuous. Imagine youve just spent 5 minutes fiddling with the knob to get your preferred upright position. After working for a while, lets say you want to watch a cat video a perfect opportunity to give your back a bit of rest. In order to recline, you turn the knob a few times to lower the resistance. Big mistake. You see, there is no back button that lets you just go back to your previous backrest resistance. When youre done watching that video, youre going to have to painstakingly recreate the original position of the knob with no visual or tactile cues to guide you. Try it once, youll never do it again. Even putting that aside, the fact that you typically have to turn the resistance knob several times to go from a near-upright to a reclined position will surely dampen your enthusiasm for healthy position changes.
There are chairs with discrete resistance controls, but I havent seen one where the number of steps would be smaller than 7. This means that youll have to turn the knob through a few clicks before you go from upright to reclined. Turning a knob 3 steps left every time you want to recline, and then 3 steps right when you want to be upright again, while dramatically better than the continuous option, is still not the height of convenience. A good chair should make it super-easy to change positions; otherwise, the user will just avoid the hassle and work in the same position for hours, which is a complete ergonomic disaster.
Well, what about locks and tilt limiters? Dont they help? Lets define our terms first. A lock freezes the backrest so that it can move neither forward nor back; typically, this is enabled by pushing the backrest into the desired angle and then engaging some kind of lever. A tilt limiter is a hard limit on the backward movement the backrest can still move forward; typically, you select one of a few angles using a lever or knob. These mechanisms have some problems, most of which are not inherent, but rather the result of the way they are typically implemented:
JE Group Product Page
- The lock/limiter control often isnt terribly easy to reach. This is a real problem because it discourages you from changing your position.
- It may be necessary to perform some extra gymnastics before the chair will allow you to disengage a tilt limiter or a lock. For example, on the Aeron, you have to bend forward (see video example). Other chairs may have other mechanical constraints.
- If you set your backrest to a low resistance and rely on a lock/limiter to stay upright, it will be hard to go from a reclined to an upright position. The backrest wont provide a lot of forward force, so youll have to work your abs (compressing your spine in the process).
- If you set your backrest to a high resistance and rely on a lock to stay reclined, you will have to use a lot of force to effect a recline that you can lock into (again compressing your spine).
- If the backrest does not have a lot of inherent flexibility, a tilt limiter or lock can freeze your back in one position without the possibility of micromovements (which is suboptimal for reasons detailed below). Hitting a tilt limit can also feel unpleasant (heres a video example).
Large hip angle
When youre sittting upright, your lumbar spine is actually bent, putting backwards pressure on your intervertebral discs. The degree of flexion depends on the angle between your thighs and your trunk (the hip angle). Your spine is in a neutral position when the hip angle is 135°.
Therefore, it is good to have a chair that opens up your hip angle as you recline. The fact that a chair has a good recline angle does not mean that it opens up your hip angle. For example, in the Herman Miller Aeron chair, the seat tilts back almost at the same rate as the backrest if you recline by 10°, the seatpan will also tilt back by something close to 10°. This means that, at maximum recline, the hip angle is only a bit larger than in the upright position! Reclining on the Aeron is still beneficial, because youre transferring load from your spine to the backrest but its not as beneficial as it could be if the chair also let you un-flex your lumbar spine.
Micromovements (rockability)
Its a good idea to pick a chair which allows you to rock back and forth around your chosen backrest position. Small movements are gentle exercise for your core muscles; they also improve your circulation, delivering more oxygen into the brain though obviously they cannot replace standing up and walking around, for example.
The nice thing about chairs with smooth backrest mechanisms is that they give you micromovements for free (except when youre using a lock or a tilt limiter). Heres an example clip from an online video on the Herman Miller Embody:
Chairs with sticky backrests, by nature, are not very good in the micromovements department. The backrest maintains its recline angle until you exert significant force. However, many chairs of this type have flexible backrests which permit limited back-and-forth motion. Heres a Steelcase Leap, which is pretty good for a sticky chair:
This is definitely less fun and less healthy than rocking with a smooth backrest, but its better than nothing.
Sticky or smooth backrest a recap
Ive said a lot of different things about sticky and smooth backrests, so lets recap the unique strengths of each backrest type:
- A smooth backrest gives you rockability (but only in one position, because youll probably want to use the tilt lock/limiter to stay upright, which makes it impossible to rock)
- A sticky backrest gives you easier switching between positions (you dont have to mess with any knobs or levers) and allows you to pick any position (not just one of the pre-defined positions)
From a spine health perspective, easy position switching is probably more important than micromovements therefore, speaking in the abstract, chairs with sticky reclining mechanisms have an advantage. In practice, however, it all comes down to the particular implementation: how fiddly is the tilt limiter? how much micromovement does a sticky backrest allow? how sticky is it? etc.
Lumbar support
As discussed above, when youre sitting upright, your lumbar spine is flexed. This flexion pushes your intervertebral discs backwards, where they can eventually bulge out and press on your nerves. The best way to un-flex your lumbar spine is to stop sitting in an upright or near-upright position unfortunately, this kind of position is more or less necessary for intensive computer work. There is, however, a way to mitigate the problem a chair with a lumbar support will reduce lumbar flexion in the upright position.
Here is a figure from Jay Keegans classic paper. Note that going from a basic chair (C) to a chair with lumbar support (B) brings you closer to a neutral position. (The neutral position is not pictured, but its about halfway between A and B.) The difference is not enormous, but its not insignificant, either.
Therefore, an ergonomic backrest should be shaped in a way which fills your lumbar curve. There are two dimensions to this. First, the depth of the lumbar support should be sufficient (and preferably adjustable) generally as deep as possible without causing discomfort over longer sitting sessions. Its better to err on the side of more prominent support, because the health consequences of slouching your lumbar spine are more serious than those of maintaining an excessive curve. The vast majority of office chairs advertised as ergonomic do not offer lumbar support of sufficient depth.
The second dimension is the height. The critical area which needs to be supported is the lowest two lumbar vertebra, because thats where 95% of all spinal herniations occur. To locate it, reach to your back and feel the top edge of your pelvis (posterior iliac crest). You can also try to feel the first vertebra that comes out of your sacrum (its easier to do this when bending over). If the lumbar support is too high, it can leave a gap and allow the lowest two lumbar vertebra to flex. As a rule of thumb, I would disqualify any chair in which the apex (most protruding part) of the lumbar support is more than 20 cm (8 inches) above the seatpan.
Many chairs have height-adjustable lumbar supports. This is generally a good idea, because peoples spines come in different heights. However, lack of vertical adjustability is not a dealbreaker. It is possible to design a chair that has a fixed lumbar support at a height that works for most users.
In most chairs, a lumbar gap appears between your lower back and the backrest as you recline. This is caused by the fact that the backrest doesnt rotate around the point where your back rotates (which is close to the point where the backrest meets the seat). It rotates where the mechanism is located, which is somewhere under the seat. This difference in centers of rotation means that the lower part of the backrest has to move further and further away from the seat as you recline. This means that your lower back has less and less support. Heres a quick visual explanation:
Some chairs, like the Humanscale Liberty or Steelcase Please, have a special construction that eliminates this, and on the better chairs, this will be not so much a gap, but a gradual loss of support (I think it depends on the center of rotation, and possibly on other mechanical considerations, as well as the adaptability of the backrest).
While good lumbar support across the whole range of recline can significantly increase your comfort level, I do not think it is a serious problem for spine health if a chair doesnt have it. Although in the upright position your lumbar area should always be supported to prevent flexing that part of the spine more than it needs to be flexed, in the reclined position this is less important for two reasons: (1) the weight borne by the lumbar spine is much smaller (the backrest bears a large part of it), and so the pressure on intervertebral discs will be smaller as well, and (2) your lumbar curve automatically deepens in the reclined position, so slouching becomes harder. (I imagine a lumbar gap could be a problem for back patients who are sensitive to motion in that part of the spine.)
Backrest flexibility
People have very different backs. Whats more, each persons back changes its shape depending on the recline angle (the spine does not work as a single unit). That is why any ergonomic chair worth its salt must have a backrest that adapts to your back. The two most common implementations are flexible plastic backrests (Leap, Gesture) and mesh backrests (Humanscale Liberty, Herman Miller Aeron). Both can work very well, with the mesh backrests having the added advantage of much better airflow.
Some chairs also have a knob that increases or decreases the curviness of the backrest, as in the Leap and Embody. This is good (more adjustments is always better in my book), but not essential.
Seatpan
The seat pan should not come up to your knees. A seat pan thats too short is better than one thats too long. A too-long seatpan will make it harder to move your legs (remember, its healthy to change position) and to get out of the chair. It is just not very comfortable. A short seatpan will be fine because people sit on their butts, not on their thighs.
According to conventional ergonomic wisdom, the seat pan should tilt back a little when you recline. When you push your back against the backrest, your butt will go up. A tilted seatpan stops it from sliding forward. I dont think its a big deal if the seatpan doesnt tilt (Humanscale Liberty) or tilts in an almost imperceptible way (Steelcase Leap, Think) but then I would recommend choosing a high-friction fabric to prevent slipping. For reasons described in the hip angle section, the seatpan should not tilt too much otherwise, it will prevent you from opening up the angle between your legs and torso. Another issue is that when the seat tilts, your butt will drop down with respect to your desk, which can make it harder to use the keyboard and screen.
Be careful with chairs that have adjustable seatpans. On some models, it is possible to slide the seatpan forward so far that you can no longer comfortably sit with your butt all the way back because you end up falling into a hole.
Armrests
The way I see it, armrests on an office chair achieve two things:
- They take some load off your spine. Your arms weigh something like 5 kg. Im not sure if your spine will notice the difference, since it normally bears more than 50 kg (the weight of your head and torso), but multiply it by 40 years of sitting and it could add up.
- They increase your precision when using the mouse. When your forearm is resting on something, you can move the mouse pointer more accurately. This is most apparent when playing reflex-based games (first-person shooters, real-time strategy games).
On the other hand, armrests can have serious disadvantages. The most important one is that hard, poorly adjustable armrests can cause permanent disability. I have actually met a guy who permanently damaged the ulnar nerve in his arms by resting his elbows on armrests now his hand movement is impaired and hes officially disabled. If youre going to use armrests, make sure theyre soft. Be sure to adjust them so that theres no pressure on your ulnar nerve (the same nerve that causes the funny bone effect). Its also probably good if they are sloped toward the back, so that the bulk of the weight is on your forearms, rather than your elbows.
When you recline, the armrests should stay relatively level. If they tilt together with the backrest, they will tear your hands away from your desk (see picture on the right). A small amount of armrest tilt is acceptable if the armrests are soft, you may still be able to keep your hands on your desk fairly comfortably. In fact, I only know two chairs in which the armrests stay totally level, regardless of the angle of recline the Steelcase Leap and Steelcase Think.
Theres also the issue of personal preferences. In my experience, there are two kinds of people: those who like armrests and those who dont. If you are in the latter group, you could consider yourself lucky. Its much easier to find a good chair if you dont care about armrests.
In general, my opinion on armrests is that if youre going to use them, they have got to be very good armrests. Heres what this means:
- must be soft (prevents ulnar nerve injury)
- not too much friction (otherwise, its hard to move your mouse while resting your forearms on them)
- they cannot prevent you from pulling up your chair as close to your desk as you like (i.e. avoid long armrests that dont slide backward far enough) otherwise, you may be inclined to leave a gap between your back and the backrest to compensate, which encourages slouching
- it must be possible to adjust them inward so that you can comfortably rest your forearms on them while keeping your fingers on the home row when touch typing (this eliminates at least of 50% of armrests most are too wide)
- when you recline, they should stay relatively level
- fine-grained height adjustment, so that you can position them just below your desk level (your arms have to be supported, but you should also be able to easily take your forearms off them if you need to make large movements)
Its pretty hard to find armrests that meet all of these requirements. The armrests on the Herman Miller Aeron tilt as you recline, tearing your hands away from your desk. The Embodys are too long and wont let you sit close to your desk. Even the Steelcase Gesture, with the most adjustable armrests on the market, isnt perfect the rubbery material has too much friction. The only armrests that have no real weaknesses are the 4-D Steelcase armrests found on the Leap, Amia and Think (the Think version is a bit harder and doesnt have as much in/out adjustability, so its a bit worse). If you dont like those armrests, you dont like armrests, period.
Recap (the Tom Test)
Heres a checklist of features that a good chair should have:
- Easy changing between at least two positions (near-upright and reclined)
- Open hip angle in the reclined position (at least 125°)
- Micromovements (rockability)
- Lumbar support
- Seatpan must not be too long
- Backrest should adapt to your back
- Armrests (if you care about them) see Armrests
- No annoyances (poor thermals, fiddly controls, hard edges, etc.)
And I hope you havent forgotten Rule Number One: Never buy a chair without trying it out first in your own workspace!
How to sit on your ergonomic chair?
See my back health FAQ, especially this question.
Chair reviews
In this series of blog posts, I will be posting short reviews of popular ergonomic chairs that Ive had the opportunity to try out in my workspace. Stay tuned!
Want more information on Multi-angle 4D Armrests mesh chair? Feel free to contact us.
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