You bought a chair sold as ergonomic. The lumbar pad lands on L3 to L5. The back, hips, or shoulders still hurt. Seat height is usable. The pad is not the miss.
If the pad sits too high, too low, or never touches the low back, start on Why a Chair Lumbar Doesn't Hit. This page is the next problem.
If you still need to shop after you count the four things, start with Best Ergonomic Chairs Under $400.
The rule is simple: count seat depth, recline lock, armrest height, and how long you stay in one posture. If those four are wrong, cranking lumbar when the pad already hits will not fix it.
What "still hurts" actually is
Still hurts here means the pad already contacts the inward curve of the low back, and something else still loads the hips, the knees, the upper back, or the shoulders. The chair can be labeled ergonomic. The pad can sit in the right band. The seat, the lock, the arms, or the hours can still be wrong.
That's different from a pad miss. A pad miss is height, depth, or chair size keeping the support off L3 to L5. That page already exists. This page does not rewrite it.
It's also different from a feel ranking. A chair can have the right pad height and still cut the knees, lock you upright, shrug the shoulders, or hold one angle all day. This page does not rank feel. It separates the four leftover causes.
Keep the four causes separate. Mixing them is how people buy a pillow for a seat-depth problem, or a headrest for a lock that never opens.
Seat depth, recline lock, armrests, time
Seat depth. Seat depth is how much thigh the pan supports when you are against the backrest. Too long and the front edge hits the backs of the knees, or you slide forward to make space. Too short and the thighs hang, the pelvis rotates, and the hips take the load. The pad can still hit. The seat is still wrong.
UPLIFT's Clarksville manual tells you to sit against the backrest and leave about an inch between the seat edge and the backs of the knees before you touch lumbar. That order is setup, not a test this page ran. Depth first. Then the pad.
Recline lock. A lock that stays upright keeps the torso stacked over the discs. Opening the back a few degrees shifts some load onto the chair. A lock that never opens, a tension setting you cannot move, or a chair with no useful recline is not a lumbar problem. The pad can land and the discs still take a locked, upright day.
Armrest height. Arms that sit too high shrug the shoulders. Arms that sit too low drop the elbows and dump the load into the upper back and neck. The Clarksville manual says to set the armrests to elbow height with the forearms near 90 degrees. If the published travel cannot reach that height, the control is the wrong tool. A missing inch range is not an infinite range.
Sitting too long at one height. One locked recline plus a desk that never changes height is one posture. A chair that cannot change angle is the same problem with fewer levers. This page does not invent a medical hour limit. The leftover fact is mechanical: a lock that never moves, and a work surface that never rises or drops, keep the same joints under the same load.
UPLIFT Clarksville and Sihoo Doro C300
These two chairs are the spec contrast this page can name. This is not a pick list. This page does not say which chair feels better. WorkstationSetup has not sat in the C300 for this page. Existing Clarksville notes live on the UPLIFT Clarksville review. They are not repeated here.
UPLIFT Clarksville (CHR475). UPLIFT's current product page and the CHR475 spec sheet agree on the controls this page cares about.
Seat depth: usable 17.3 to 20 inches, with a documented left-side slider. The instruction manual says to pull the left paddle and slide the seat, then leave about an inch at the knees.
Recline: 2:1 synchro-tilt, three tension levels, five locking positions, up to 40 degrees. The product page names recline locking and the 2:1 ratio (2 degrees of back for 1 degree of seat). The manual tells you how to unlock, lock at an angle, and return upright. That is a usable lock set, not a missing recline.
Armrests: three-way, height, depth, and pivot. The CHR475 spec sheet prints two arm figures: an arm rest adjustment range of 7 to 10 inches, and an arm adjustment range of 3 inches. This page does not invent a third number. The manual describes a button under each arm for height, a slide for depth, and a rotate for angle. It does not reprint those inches.
Other Clarksville figures that do not conflict: seat height 17 to 22 inches, back 18 inches wide by 22.5 inches high, overall height 39.3 to 44 inches, 300 lb capacity. There is no headrest. Four lumbar height clicks exist on this chassis. They are not the topic of this page.
Sihoo Doro C300 (standard, current US page). Sihoo's current US product page names a self-adaptive lumbar, 4D coordinated armrests, a weight-sensing recline, and an adjustable headrest. Several numbers need the weaker reading.
- Seat depth. The current US page lists 17.13 to 18.11 inches. It does not clearly identify a user-operated slider. This page keeps that range as published geometry, not as a confirmed sliding seat.
- Recline. The current US spec table does not print a degree number. It names a weight-sensing mechanism. Official UK and EU shops list 110, 120, and 130 degree lock angles. This page does not treat 130 degrees as a confirmed US spec.
- Armrests. The current US page names 4D coordinated armrests: up and down, left and right, forward and backward, and tilt linkage. It does not publish armrest height travel in inches. A 4D label is not a measured window.
- Back height. The current US page lists chair back lifting height at 18.11 to 21.65 inches. Those are backrest numbers, not a seat-depth or armrest figure.
- Capacity. The current US page lists 330 lb. Official UK listings list 300 lb. This page does not rest a fit argument on those two numbers.
The published contrast is the control, not the comfort. Clarksville documents a seat-depth slider, a five-lock recline with a printed 40 degree top, and two published arm figures. C300 publishes a narrower seat-depth range that may not slide, a recline with no US degree number, and 4D arms with no published height travel. If you need a documented C300-line slider, that control is on the Pro and Pro V2 pages, not on the standard C300 US spec table.
What will not fix it
A few common next steps do not change seat depth, recline lock, arm height, or time in one posture.
A new pillow. Extra foam behind the low back does not shorten a long seat, raise a low arm, or unlock a stuck recline. If the pad already hits, the pillow is the wrong tool.
Buying a more expensive ergonomic label. A higher price or a longer feature list does not prove the seat will fit your thigh, the lock will open, or the arms will reach elbow height. Confirm the published controls before you pay more for the word ergonomic.
Cranking lumbar when the pad already hits. Height clicks and a self-adaptive label move or follow the low back. They do not slide the seat, change the lock, or raise the arms. If L3 to L5 already has contact, more lumbar is not the leftover problem.
A headrest for a seat-depth problem. A headrest holds the neck when you recline. It does not make a long pan shorter or a short pan longer. The C300 US page includes an adjustable headrest. The Clarksville has none. Neither fact fixes a seat that cuts the knees or dumps the thighs.
What can change load, as setup, not as a test this page ran:
- Sit all the way back. Leave about an inch at the knees. If you cannot, the leftover check is usable seat depth, not another pillow.
- Unlock the recline and use more than one lock, or leave the lock open if the chair allows it. A lock that never moves is one posture.
- Set the arms to elbow height. If the published travel cannot get there, the control is the wrong tool.
- Change the desk height if the desk can move. A locked chair on a fixed desk is still one posture. Existing UPLIFT desk coverage lives on Which UPLIFT Standing Desk Is Right for You.
When this chair cannot do the job
Count the four numbers.
- Seat depth: If the shortest published depth still cuts the knees, or the longest still dumps the thighs, the pan is the wrong size. A 17.3 to 20 inch Clarksville slider can still be too long or too short. A 17.13 to 18.11 inch C300 range is a narrower published band, and it may not slide.
- Recline lock: If the chair has no useful unlock, or every lock keeps you stacked upright, the mechanism cannot share load with the backrest. Clarksville publishes five locks and 40 degrees. C300's US page publishes no degree number.
- Armrest height: If the arms cannot reach elbow height, or they cannot drop enough to un-shrug the shoulders, the control is the wrong tool. Clarksville publishes 7 to 10 inches and 3 inches. C300 publishes directions, not inches.
- Time at one height: If the recline cannot change angle and the desk cannot change height, you have one posture. A chair label does not create a second one.
If seat depth, recline, arms, and time are all wrong, this chair cannot do the job. That is a different chair or a desk that can change height, not a different pillow.
If you still need the spec split after this page, start with UPLIFT Clarksville vs Sihoo C300. Existing Clarksville notes live on the UPLIFT Clarksville review. This page does not rewrite either one.
Where to go next
This page does not add a pick list.
If the pad misses L3 to L5, use Why a Chair Lumbar Doesn't Hit.
For the foam-seat vs full-mesh spec split, including the C300 seat-depth caveat, read UPLIFT Clarksville vs Sihoo C300.
For the C300-line slider that the standard US page does not clearly document, read Sihoo C300 vs C300 Pro vs C300 Pro V2.
If you still need to shop after you count seat depth, recline, arms, and time, use Best Ergonomic Chairs Under $400 or Best Ergonomic Chairs Under $600.
If the leftover problem is a desk that never changes height, start with Which UPLIFT Standing Desk Is Right for You.
If the pad already hits and the chair still hurts, start with the leftover mismatch. Count seat depth, recline lock, armrest height, and time in one posture before you buy another accessory.