Seat Depth Adjustment - The Big, Fat Misunderstanding

Seat depth adjustment is often overlooked... and when not, it's misinterpreted.
But the issue is that is can cause back pain... serious back pain, I mean!!
There's in my opinion a big misunderstanding on the topic. Including among ergonomists.
The usual rule is that you should have one fist between the fold of the knee and the front edge of the seat pan. As a result, many tend to slide the seat forward.
00:00 intro
00:35 the ergonomic rule
00:58 the issue with the rule
and why it can harm your sitting posture
02:28 pain when violating the rule?
03:39 the real rule
04:08 how to adjust seating depth
05:42 inventing a new chair
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A lot of the pain you feel is caused or aggravated by wrong posture, poor ergonomics and a lack of specific exercises for your muscles and joints. Giving you the tools to resolve these issues is the reason why I created this self care channel.
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All information, content, and material of this website is for informational purposes only and are not intended to serve as a substitute for the consultation, diagnosis, and/or medical treatment of a qualified physician or healthcare provider.
Full disclaimer:
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[@silverfire01]

Great video. I have just bought my first seat slide chair. Only due to fact that can't rely on retailers when quote seat depth as they mostly don't deduct the thickness of the backrest from the seat depth quoted.

[@OlivierGirard]

you're 200% right indeed: seat depth is very difficult to evaluate from the specs so I tend to measure manually from the vertical of the lumbar support most forward point. But online, it's difficult to judge indeed.

[@silverfire01]

@@OlivierGirard am not sure why manufacturers don't give the sitting depth. I know could never be 100 percent accurate especially if has adjustable lumbar support but at least would be better than stating a seat depth then having to deduct 5cm or more because of the backrest. Hopefully the chair that I ordered seat depth is correct 48cm to 53.5cm with seat slide and not 43cm to 48cm with backrest. I wish I had seen your video before ordering .

[@BeeyothGaming]

Thank you so much for this video! I bought the steelcase leap v2 about 2 months ago now, and I've been having consistent discomfort with it no matter which area I adjusted. The thing I never adjusted was the seat depth though. I was under the impression that since I'm 6'3, I should have it all the way forward. For the past few days, I've had my seat depth 2 clicks back from the most forward position. It has helped dramatically!

[@willsander6178]

I'm only 6'0 but I can relate. Under the impression I should be far forward, about two clicks down in my humanscale freedom. I think that was wrong... I always wondered why Humanscale would say "Fit a fist or three fingers between your legs and the seat" but would only say "adjust backrest to whatever is comfortable"! Now I think I understand.

[@odietamo314]

When you made the gap between the seat and back rest I was like "yes! this is exactly what i want!" And then you said "no one wants to sit in the gap," which made me laugh, because me and my huge butt disagree! Most chairs that i have encountered (which is not that many) do not have enough of an adjustable range for lumbar support on their own, and so i rely on the adjustable seat depth to create more of a gap, so that i can actually get the benefits of the lumbar support. I do agree with you on the point that this can cause too much pressure toward the knee. But for me, the back support is more important, and i can mitigate the pressure problem by getting up and walking around for 10 minutes every hour. Sadly, most chairs that fit heavy people are also designed for tall people, there aren't really any options for us short heavy people.

[@FortuneOnTV]

Bonjour Olivier, je vous remercie énormément pour vos vidéos qui mon aider à améliorer la qualité de mon quotidiens, je discute souvent maintenant avec mon entourage sur comment avec quelque geste nous pouvons rendre notre journée au bureau plus agréable. Même durant mes stream je me retrouve à discuter d'ergonomie au lieu de discuter de jeux ahhah ^^ Merci encore de partager vos connaissance sur youtube o/

[@Fedex8016]

Hi Olivier Many thanks for all your videos! When I sit in my office chair for some reason my calf muscles start to hurt really bad, particularly on the sides (the peroneal muscles). I was thinking maybe this is because of the depth of the seat as I am also a petit user (5.1 ft). What do you think? Maybe there are other reasons behind my pain?

[@willsander6178]

Holy... I'm about 6'0 and I've struggled with my Humanscale for about two years... I've tried to be warry about having it too far in any direction and have tried doing calculations (divide height range (5'0 - 6'4) by number of clicks seat pan can go back (9)) to find what should be the right setting for me, thinking it's about two to three clicks back. I was aware that it may not scale linearly but still assumed this information to be about correct. But upon trying the seat pan ALL THE WAY BACK I immediately feel very very different to how the chair usually makes me feel! It's like I don't even feel anything on my back, it's insane. I'm going to increase the seat depth from here, obviously, especially since I feel not too amazing leg and shoulder wise at the moment, but wow! Thank you!

[@OlivierGirard]

Well done! That's how I adjust it for my clients too: start all the way from the back, feel the pressure in the lumbar area, and then move it forward one click after the other. As soon as the pressure in the back drops, it means you transfer less weight to the chair, i.e. more weight stays on you. So you go back 1 click and you're fine :)

[@lisasmith458]

Hello. I have a synchro office chair (operators chair) which I have a hard time finding a comfortable position adjusting to fit me as a petite user. How do I find the correct angle of the seat pan so my weight is evenly distributed when sitting? I have suffered with typical neck shoulder pain for 3 years. I look forward to hearing from you.

[@OlivierGirard]

Hey Lisa, that's a great question... for which I have no generic answer. Basically, you'd like the seat pan to be around horizontal. BUT: on a synchro chair, the backrest angle is predefined by the manufacturer. On a chair like mine, I have good back support with my seat pan horizontal, but on a chair like the Giroflex 64 (www.architonic.com/en/product/giroflex-giroflex-64-4578/1068702), the backrest is then super far away. In other words, you'll have to have a forward tilted seat pan if you want a lumbar support (which is the reason why I don't recommend that chair). Does this answer your question a bit?

[@lisasmith458]

@@OlivierGirard absolutely. Now I know why the backrest always seems so far away I can never get it to fit my back. It isn't the best chair and unfortunately they supplied the entire office with them which is a poor choice. Should I add a external lumbar cushion to rectify this solution?

[@OlivierGirard]

​ @Lisa Smith it could help indeed, if you manage to attach it well to the backrest. A cushion with 2 straps will be more stable than on e with just 1 ;)

[@Dougggggggg]

Hi, I have a Herman Miller aeron size C. I'm 6'2" in height and have 3 fingers width between the back of my knees and the edge of the seat. Unfortunately the seat is causing intense pain on the bottom of my thighs after sitting for only 20 minutes. I have the seat height at 18 inches to achieve 90 degree angle between knee and hip. Any recommendations? Thanks.

[@OlivierGirard]

On this chair model, it can also be that the seat pan is tilted backwards, which creates pressure under the thighs. Most people I see with this chair haven't discovered that function: it's here, on the top left of page 2 www.hermanmiller.com/content/dam/hermanmiller/documents/user_information/classic_aeron_chairs_adjustment_guide.pdf . Try that and let us know...

[@Isaxus12]

I'm the same height and have the same problem with IKEA Markus, I wonder if its seat pan is unusually tilted...

[@Martin1lion]

Can you recommend a chair for a tall person 205cm 105kg ? I like Jarvfjallet from ikea but depth adjustment is not deep enough. Im located in US.

[@OlivierGirard]

The BMA Axia 2.4 is known to be quite adapted to tall people: it has a few options you may consider i.e. tall gas spring, XXL seat pan, XL armrests. Not exactly the same price as Ikea, but you'll keep it for many years...

[@Martin1lion]

@@OlivierGirard thank you but can't find this model in US

[@salvaru6581]

which chair can u recommend to buy ? price is not a problem

[@OlivierGirard]

this is a tricky question: the offer depends on where you live. Check out the brands I list on this page: oliviergirard.ch/en/technical-specs-furniture/