It has come to my attention of that some anatomists applying
the concepts of tensegrity to the human body are suggesting
that bones in the body float in a sea of tension - in much
the same way struts in the Kenneth's Nelson's sculptures are
suspended in the air and without direct contact with other
Stephen Levin is one of the proponents of the idea.
He explains it as follows:
The support system of the spine, and indeed the remainder of
the body as well, is a function of continuous tension,
discontinuous compression, so that the skeleton, rather than
being a frame of support to which the muscles and ligaments
and tendons attach, has to be considered as compression
components suspended within a continuous tension network.
The author developed a model of the spine in which the bones are
not in contact with each other - and instead are supported by
a tensile network, presenting it with the following abstract:
The commonly accepted 'tower of blocks' model for vertebrate
spine mechanics is only useful when modeling a perfectly
balanced, upright, immobile spine. Using that model, in any
other position than perfectly upright, the forces generated
will tear muscle, crush bone and exhaust energy. A new model
of the spine uses a tensegrity-truss system that will model
the spine right side up, upside-down or in any position,
static or dynamic. In a tensegrity-truss model, the loads
distribute through the system only in tension or
compression. As in all truss systems, there are no levers
and no moments at the joints. The model behaves non-linearly
and is energy efficient. Unlike a tower of blocks, it is
independent of gravity and functions equally well on land,
at sea, in the air or in space and models the spines of fish
and fowl, bird and beast.
He seems to show some understanding of how radical his
A rigid, axial-loading, gravitationally oriented support
system cannot be utilized as a model for animated
structures, including the human spine. A model based on
Buckminster Fuller’s tensegrity icosahedron, which
demonstrates the principle of continuous tension,
discontinuous compression, may also be utilized to
demonstrate the structural integration of the body. All our
previous concepts of biomechanics of the body will have to
be reassessed in relation to the model and our therapeutic
approaches to the musculo-skeletal system will have to be
What about the fact that it is a well known anatomical fact
that bones in the spine and legs bear weight in compression
Apparently, Stephen has been present at operations, and observed
that the bones in quesion do not touch each other when axial
compression forces are applied:
Although some of the rigid components of a tensegrity system
may "kiss," it does not mean that they are in compressive
opposition to one another. Axial loads were applied to
joints in live subjects under anesthesia during surgical
intervention for a variety of conditions. Joint studies
included the knee, ankle, elbow and metatarsal-phalangal
joints. In our studies at no time could the articular
surfaces of these joints be forced into contact with one
another as long as the ligaments remained intact. Although
the study may lack elements of sophistication, it is readily
reproducible by any surgeon.
If there is no phyiscal contact, it is hard to imagine how
compression forces could be transmitted.
The spread of the idea
Levin's ideas seem to have been adopted by some others. For
example, here is Tom Myers - author of the book Anatomy
Trains - claiming that bones 'float':
Instead of what we're used to, which is a brick sitting on a
brick sitting on a brick - and that's how you make a
building. With tensegrity structures, the bricks, the
sticks, float in a sea of rubber bands and they stay where
they are because of the balanced tension between the rubber
In the past, we have thought of our bodies as a stack of
bones with the muscles hanging off of it like the cables of
a crane. And it's not that way - the bones float in the
soft tissue. It's those tensegrity structures that give us a
geometric model to see how that works.
Stuart Bell explains the appeal of the idea as follows:
Most often we think of structures and build structures as
one segment piled on top of another supported by gravity,
for example brick homes. Compressional thinking is deeply
ingrained, due perhaps to an easy experiential knowledge of
this phenomenon from early childhood. Even the word
structure is derived from the Latin struere which means to
heap up or pile up. As a result, we unconsciously think of
our bodies as built like that, as compressional structures,
where the segments of the body stack one on top of another
and where the bones are compressed directly against one
another. This model works pretty well but it lacks finesse
in describing all of the characteristics of human structure
and movement. Many of us take on a “compressional” look in
our bodies and postures. Our weight often looks passive and
heavy. We look tired, as if gravity were not the ally it can
be but an arch enemy instead.
Using Tensional Integrity as a model for bodies, where
gravity acts as a friend, offers a beneficial alternative.
Such a structure depends for support on a tensional-fabric-
network where bones float in this sea of fibrous connective
tissue and where the fabric in turn is seen to float in an
ocean of fluid called the ground substance. Buckminster
Fuller’s posits that such structures are more efficient in
many ways, requiring a minimum of building material. [...]
When we conceive of ourselves as built by compression, the
image could leave us with a heavy sense or feeling. In this
sense gravity could be considered mostly as a downward force
and perhaps the enemy. We might think of our aches and pains
as local incidences, due to accidents, and localized
structural failure and not be able to see the structure as a
whole, not treat the whole body-mind continuum. We might
become focused on single areas and lose our overall,
connectedness perspective. We might also expect to have lots
of problems where these compressional elements meet, at the
joints and not look for causes from further afield.
The ubiquitous bone, muscle, fulcrum, and pulley model that
pervades current thinking has served as a useful model when
used within its bounds. But, improperly understood this
model causes us to demand support from our bones and spine
which is not healthy and causes much suffering in human
spines and joints. Perhaps tensegrity can help.
Imagine our cells and the structure of our bodies all
relying on a Tensional matrix for their Integrity,
structure, support, well being, and communication. In the
body we call this matrix connective tissues. The connective
tissues respond to forces by sharing tension throughout the
entire tensional fabric of the body, just as do the
structures you see modeled here in the pictures below.
Tensions, aches, and pains we feel in one area of our body
connect everywhere in the body fabric, and they are often
caused at some other surprising and unexpected locations.
Gone are the days when working on separate parts alone will
do without considering the effect upon the whole. The whole
system all the way to the cellular and nuclear levels needs
be addressed. In structural integration we see that proper
organization in connective tissue leads to a balanced body
and adds vibrancy to our cells.
Right. I can imagine how one can see gravity as the enemy,
compression as its weapon and floating-strut tensile
structures as salvation.
Having noted that this perspective has some attractions,
we must now address the issue of its scientific accuracy.
On that front there can be no mistake - the idea is a
load of utter nonsense.
It is not accepted by the medical profession or the
scientific community. Instead, it is promoted by a few
enthusiasts - who seem to have skipped over attempting to
gain scientific respectability for the idea - and are
instead marketing it bodyworkers - perhaps a group
identified as being scientifically naive and open to
swallowing new-age claptrap.
Vertebrae do not 'float in a sea of tension'. At least not
unless you are hanging upside down from a tree. Instead,
they bear down on each other in compressive stacks.
Measurements of intervertebral disc pressure indicate that
the pressure depends strongly on whether the subject is
standing or is supine:
Disc Pressure Measurements Prove That the Pressure on the Disc
is 11 Times Greater When the Patient is Erect
Another study - looking at L3 rather than L5 confirms this:
"The main function of the disc is mechanical. The disc transmits load along the
spinal column and also allows the spine to bend and twist. The loads on the
disc arise from body weight and muscular activity, and change with posture
(see figure 6.8)."
How much of the weight is borne by the compression forces in the intervertebral discs?
Most of it:
In the erect posture, 80 to 90 percent of the axial compressive force
is absorbed by the anterior column of the normal spine
- Full text of Fracture-Dislocation of the Lumbar Spine After
Arthrodesis with Instrumentation for Idiopathic Scoliosis. A Case Report
Jeroen G. Neyt And Stuart L. Weinstein - obtained via Google.
Eighty percent of the load transmitted through the
lumbar spine passes through the anterior column
- Full text of Transforaminal Interbody Fusion Versus Anterior-Posterior
Interbody Fusion of the Lumbar Spine: A Financial Analysis -
Journal of Spinal Disorders. 14(2):100-103, April 2001 - obtained
Discs connect one vertebral body to another to
allow motion of the spine and cushion it against
heavy loads. Together, the vertebral bodies and
discs bear about 80 percent of the load to the spine.
The anterior cylindrical bodies of the vertebrae, which are spaced
apart by intervertebral disks, bear most of the compressive load
of the spinal column (approximately 80 percent of the total load).
Furthermore, under normal circumstances, intervertebral
discs support approximately 70-80% of axial loads imposed
upon the lumbar spine, whereas the rest of such axial loads
fall on spinal structures including, among others, the facet
Biomechanical studies demonstrate that the anterior spinal
column consisting of vertebral bodies and intervertebral
discs bear most of the body weight in the upright position
while the facet joints bear up to 16% of the axial load.
A 'floating bone' model - like the one on
...that totally ignores the possibility of axial
forces in the spine cannot possibly be correct.
Also, that diagram shows the weight bearing ligaments as
runing from the spinous prcesses to the transverse processes
of the vertebrae below. I have not been able to find any
evidence that such ligaments exist. Between vertebrae,
there are supraspinous ligaments, interspinous
ligaments, and the ligamentum flavum - and
various structures around the synovial joints - but none of
those run as shown in the diagram.
After discarding axial-force models of the spine, Levin has
replaced them with something so grossly inaccurate
about how the body is supported as to be totally
So much for the bones in the spine 'floating'.
What about the idea that other bones float? Since Levin had
mentioned the knee as one of the places where the bones
didn't touch, I had a look at that joint - and found:
The medial meniscus absorbs up to 55% of the
load applied to the medial compartment of the knee and the
lateral meniscus bears up to 75% of the lateral compartment
load. While walking, forces on the knee increase by 2 to 4
times body weight. These forces can increase by 4 to 8
times when running and jumping.
The meniscus acts as a shock absorber for the knee by
spreading compression forces from the femur over a wider
area on the tibia.
The medial meniscus bears up to 50% of the load applied to
the medial (inside) compartment of the knee.
The lateral meniscus absorbs up to 80% of the load on the
lateral (outside) compartment of the knee.
Load-bearing in the knee joint.
Shrive NG, O'Connor JJ, Goodfellow JW.
[...] Confirmatory experimental results show that in
partially degenerate human and healthy pigs' knees the
menisci bear at least 45 and 75% respectively of the total
joint load. The knee joint is similar in this respect to
other synovial joints.
Load bearing function:
Menisci distribute forces throughout underlying articular
cartilage, thus minimizing point contact;
Menisci bear 40 to 50% of the total load transmitted across
joint in extension and 85% of the compressive load is
transmitted through the menisci at 90 deg of flexion;
What about Levin's observation that the bones do not touch?
They most certainly do touch - if the knee menisci
- pads which carry around half the weight - are removed:
The important role of the meniscus in force transmission can
be seen when the menisci are removed.
If the menisci are removed, the forces are no longer
distributed over a wide area of the tibia. Without the
medial meniscus, the tibial contact area is decreased 50 -
70%. This means the same forces from the femur are
concentrated on a smaller area of the tibia.
When the lateral meniscus is removed, there is a 45 - 50%
decrease in contact area. This results in a 200 - 300%
increase in contact pressure, which can eventually damage
the cartilage on the ends of the bones. This can lead to
In the 1960s and 1970s, it was common to remove a damaged
meniscus entirely. This frequently led to early degenerative
arthritis in many patients.
Without the menisci, the forces are no longer distributed
over a wide tibial surface area, but over the smaller,
limited surface area of femoral tibia.
Loss of medial meniscus causes tibial contact to decrease
55-75% while loss of lateral meniscus decreases contact by
40-45%. This leads to a 200-300% increase in contact
pressure and can cause an early onset of degenerative
Bones do not 'float'.
To float in anything like the same way as the struts in
Snelson's tensegrities, they would have to not be supported
by any compression forces: after all, one does not
describe a helium balloon as 'floating' if 10% of its weight
is borne by the ground.
In fact, the compression forces supporting the standing body
account for the vast majority of the forces holding
The 'floating bone' model is a beautiful theory, spoiled by
an ugly fact: nature has no problem using compression forces
between bones for support, and does so in practically every
joint in the human body.
To suggest that the bones in the spine 'float' - in the face
of the evidence that they are supported primarily
by compression forces - seems irresponsible to me.
I am concerned that propagating this kind of false
anatomical doctrine could - in principle - cause physical
problems for people that buy into the delusion - perhaps by
causing them to underestimate the compression forces in
their spines, possibly leading to ruptured intervertebral
I encourage those involved to seek out other metaphors for
how the body supports itself against gravity. If they can
find ones which are more accurate, less misleading and
contain fewer factual errors, that would help.
Levin suggests he has had some problems getting his ideas
accepted. He puts things well:
The column-lever model has been the plush carpet under our
feet that we have stood on for hundreds of years. It is
difficult to pull the rug out from someone, particularly if
there is no floor underneath.
I've put more references - relating to how compressive force
is transmitted through the knee joint - on their own page here.
Stephen Levin has responded to my comments.
Our discussion is archived here.
Tim Tyler |