The Physics of sitting comfortably

The Physics of sitting comfortably

if you don’t like math and very basic physics, here’s the super condensed version:
1. maximize the square footage of your sitting posture base, it maximizes your ability to sit long without numbness and discomfort, up to 2 or 3 hours in my experience.
2. completely relax the body and mind, make your body like the air or water element, so soft, no tension or pressure anywhere. Fulfill the 8fold path factor of right attitude (letting go, being kind and gentle throughout the sit))

I wanted to share this insight because many of us may intuitively know this after years of trial and error, but understanding the biomechanics and some important details can be really helpful in explaining and showing others exactly why it works and how they can decrease the chances of numbness and pain.

From physics, we know:
Pressure = Force / area

The area we are concerned with for our meditative posture is our butt and upper legs mostly.
The smaller the area (of our meditative base), the higher the pressure.
The larger the area of our base, the lower the pressure.

Higher pressure => shorter meditation duration in comfort and lack of numbness or pain
Lower pressure => longer meditation in comfort free of discomfort

To lower the pressure, from the equation we see we want to maximize the area of our base. How do we do that?

First, some real world examples showing the spectrum and effect of large area base to small area base. Here’s a list from large to small:
1. sitting on a dining room wooden (mostly flat seat) chair, without leaning. (base would include butt and part of your legs)
2. sitting on a bar stool (with no back to lean on) (base is only your butt, but no more leg support)
3. sitting on a bicycle (base is even a smaller percentage of butt than the stool )
4. you’re out hiking, taking a break sitting on large uneven rock that is so uneven it feels like you’re sitting on the bike from #3 with the seat removed

In your own experience, Which of the four is more comfortable. Why? If you do the math and calculate the pressure based on square inches in area, you’ll find the math supports your experience that option #1 is the most comfortable and #4 the least so.

If you sit on a round grain filled cushion, the effective square footage of your base is significantly reduced (compared to cross leg directly on the ground). So your body weight is supported with a smaller base, it’s going to hurt sooner into your sit. Two other big problems with the round cushion. The transition points between where your meditative base ends tend to cause discomfort on the points of your legs where it jarringly transitions from  the height of the cushion to the ground instead of a gradual smooth slope. In addition, it’s easy for many guys to get numb nuts from the pressure point on the crotch. I don’t know if ladies get num ‘nads, but just from the physics I know that everywhere on the meditative base where it ends on the cushion and transitions to the rest of your leg is a pressure area subject to higher probability of hurt after long sits.

The way to maximize the area of the base is sitting on flat firm ground  (F1 footnote) so your base includes your entire butt, side of your thighs all the way to your knees. From a bird’s eye view the shape of your base would be  a generous fat and thick V-shape. The advantage over the round cushion: A bird’s eye view of the area of the base for the round cushion would show something more like a small circle using only about 50% of the square footage of potential full butt base. Smaller area => higher pressure =>  higher pain => shorter sit.

There is a problem with sitting flat in the ground if one’s flexibility in the back and hamstrings are insufficient. One will not be able to sit too long comfortably with the 90 degree angle from the cross legs to the vertical back. This can be ameliorated with 2 ways, both  of which open up the angle and relieve pressure from tight back and leg tissue.
1)     V shaped grain filled cushion (instead of the inferior round cushion design). An important detail is you want to adjust the shape of your V-shape cushion so that the angle tapers down  gradually from a higher butt area to a lower transition points where your knees meet the ground,  similar in principle to the wedge option #2. If you make it flat, it’s still much better off than the round cushion because of a larger area base, but you will have 2 stress points where the top of the V-shape on the cushion transitions to the middle of your thigh.
2)     A flat wedge seat with about a 10 or 15 degree angle. The sitting surface is mostly flat, but the incline of the wedge opens up the angle between your legs and vertical spine, removing pressure. I’ve seen one person use a manufactured plastic wedge on a retreat. One can probably make a homemade version with just a rectangular piece of plywood and something to elevate one end slightly to make the wedge shape.

A better way, but which takes more time and effort to train, is to do daily yoga so that you develop and  maintain sufficient flexibility so that 90 degree between cross leg and vertical spine is comfortable and maintainable for lengthy sits. This way, with just a towel and/or yoga mat, you can meditate indoors, outdoors, anywhere without requiring special props.

Most of my sits, I sit usually half lotus or full lotus, on a v-shape cushion, without numbness or discomfort for 1.5 hours guaranteed, 2 to 3 hours if I do 20min yoga before the sit. My  back and leg flexibility is gradually improving, and at the current rate of improvement I would estimate within 2 years I will be able to forego the assistance of the v-shape cushion altogether.

The mental part of being able to sit long comfortably depends on how well you can continuously stay relaxed mentally and physically. You’re so relaxed that you feel like your whole body is the air element, like you almost don’t even have a physical body at all, no pressure anywhere on your sitting base or anywhere else in the body and mind.  The noble eightfold path factor of right attitude sums up very well the required elements that make long sits easy and enjoyable. Having the attitude of letting go (of all tension and stress both mental and physical), being kind  and gentle (to all the cells in your body, and your mind).

Happy sitting to all.