Saturday Rehersal to sunday service — YOUR BOOTH CHAIR SHOULD KEEP UP

This is the position conventional seating is worst at. Mandal's point is anatomical: chairs assume around 90 degrees of hip flexion and most people have nearer 60, so the shortfall comes out of the lumbar spine and your lower back rounds. Lean further and the backrest stops touching you, leaving those muscles to hold your torso unaided. Soderberg's EMG work found that tilting the seat forward significantly reduced exactly that muscle activity.

A sightline problem turning into a neck problem. Bridger found that raising and sloping the work surface produced less neck flexion than making the person lean — so solving it with height rather than reach keeps the head stacked over the shoulders. He was careful to note the differences were small, but the direction is consistent.

Standing keeps the pelvis neutral, which is why it beats a bad chair. What it costs is stamina and steadiness — you are stabilising your whole body while trying to do fine work. A perch height seat keeps most of the open hip angle and gives the weight somewhere to rest.

Standard seat, 18.5 by 16.75 inches. A pan wider or deeper than your frame is not more generous, it is less supportive: the seat should end before your thigh does, or the front edge stops carrying you and starts pressing into the back of your leg.

Pro seat, 20.25 by 19.5 inches, with more cylinder travel. Both models are rated to 350lb — the difference is footprint, not strength. Too small a pan concentrates your weight into less tissue area, which is where numbness starts on a long day.

Tool-free adjustment is the whole specification for a shared chair. Set once for one body, it is wrong for every other body, and nobody re-rigs a chair before a shift — they sit badly for two hours instead.

Then fit it once, properly: seat size to their frame, cylinder height to the console, footring where their feet naturally fall. Set correctly it never needs touching again.

Feet with nothing under them leave the weight of your legs hanging off the front edge of the seat, concentrating pressure on the underside of the thigh. This is also where Hamaoui's finding bites: a forward-sloped seat increases leg-muscle load, so height without a footring trades a back problem for a leg one.