Knowledge Base → Questions → How is your weight distributed when you sit?
How is your weight distributed when you sit?
Mainly on the sit bones, the buttocks and the back of the thighs; depending on posture, also on the perineum or the tailbone. A good seat does not remove pressure: it spreads it over areas that tolerate it, avoids hard spots and lets it shift. Removing one contact area always moves its load somewhere else.
Where does the weight go?
| Area | Role | If it is overloaded |
|---|---|---|
| Sit bones (ischial tuberosities) | Main bony contact points | A painful point, burning |
| Buttocks, back of the thighs | Spread the load | Numbness, diffuse pain |
| Perineum | Should carry very little | Pain, irritation of the pudendal nerve |
| Tailbone | Bottom of the spine | Pain on contact and when getting up |
Why spread the load?
For the same weight, a larger contact area lowers the average pressure; and pressure that moves is better tolerated than pressure that stays in the same place. Pressure in the small blood vessels of the skin is low (Landis, 1930): concentrated, prolonged contact easily exceeds it.
What happens when you remove a contact area?
A central cut-out shifts weight onto the sit bones and the edges; a rear cut-out shifts it forward; a soft seat lets you sink in until you touch. This is why the area that carries the weight matters as much as the one you free up.
What if your sit bones hurt?
Check that the load stays well distributed around them, without giving up the offloading another area needs. Among the configurations that keep the necessary area free of contact, the Aporia framework looks for the one that keeps the most continuous support around the painful sit bone. A central or rear cut-out leaves the sit bones supported on either side: check that it does not increase the load on them; a continuous channel brings them closer to its edges. If no area needs to be kept free of contact, continuous support (Aporia Back Pain) is the reference. The conditions related to your contact points, your seat and how you use it are in the guide Which cushion for pudendal neuralgia?
Should a cushion be soft or firm?
Neither, as a rule: the support should keep its shape under load without hard spots. Firmness is chosen according to your sensitivity, not your weight.
What other questions do people ask?
Should the sit bones carry all the weight? No: the buttocks and thighs should share it.
Does a thicker cushion spread the load better? Not necessarily: it can destabilize the pelvis and change your seat height.
Publisher: Blue Portance. Written by Gil Ayache, PhD (Mines Paris – PSL). Reviewed: October 19, 2026. Sources: Landis E. M., Heart, 1930 (capillary pressure), cited in the Blue Portance reference framework; Aporia framework (sit bone rule of the V16 engine). Aporia® cushions are not medical devices.
Note: this content explains mechanisms related to sitting. It is not a medical diagnosis or prescription, and it does not replace the advice of a healthcare professional.
