Undulations Painted/Draped on Sidebent Spinal Curves: Transverse, Longitudinal and Torsional Waves
Lalu Simcik
article
Transverse waves are those we see in a jump rope
lying on the ground right after the rope end is
abruptly flicked. The wave packet travels like a
train on its tracks down the length of the rope.
When shaking sheets out onto a bed, we also create
transverse waves that move the sheet away from our
hands and spread it out more evenly.
Longitudinal waves can be listened to whenever a
train leaves the station. The engine car pulls
away first, and then each loose car gets pulled in
sequence, creating an audible pulse that travels
down the entire length of the train.
Torsional waves are sequential twists that travel
down the length of our spine or a long flexible
object. When we are standing and rapidly turn our
head around its vertical axis to one side, we
create a torsional wave that descends down the
body. The head twists the neck and connecting
muscles while sending a wave of torsion (twist)
that can be soon felt by the torso as it follows
the head. Immediately after this, the same wave
can be felt as the pelvis follows the torso in the
original direction of twist.
A stiff body does not allow this sequential wave
action to occur, rather, the twist will be replaced
by a solid rotation of the entire body as it moves
as one piece. Although this motion may be desired as an end
result of the torso, pelvis, and legs during a
pirouette, most ballet dancers spot their
eyes by having the head lead the torso and then the
torso lead the head. Using torsional waves in
between the head and torso, rotational undulations
rotate the cranium ahead of the torso's rotation,
then stop it at the spot point. After the torso
passes, it's energy rotates the cranium once again
to pass ahead of the torso onward to the next spot.
The viewer is mesmerized by seeing a body in full
dynamic motion, yet the dancers face appears
held in stillness. Even though the torso and
pelvis rotate together, an efficient entry,
maintenance, and exit from a pirouette requires a
spine that is available for undulation.
Transverse, longitudinal and torsional waves of
kinetic energy travel the length of our spine,
leading and guiding our extremities.
Alternatively, motions of the extremities can
distally motor the neck, torso, or pelvis, to
create transverse, longitudinal and torsional waves
of energy that travel back through the spine.
Flattening or reversing any of the three spinal
curves reduces, impedes, or inhibits the ability of
the spine to transmit these waves. Vertebrae get
stuck at their natural stops and cannot rotate.
Flattening or reversing spinal curves is metaphoric
to adding starch to a section of our jump rope, and
then trying to pass a wave through a rope that
won't take on the shape of the wave.
Sidebending maintains spinal curves which are
necessary for healthy wave propagation.
In slow movement, undulations are most visible in
the lead and lag of body parts or in the sequence
of moving vertebrae. In higher dynamic movement,
increased necessary tensions reduce the size
(amplitude) of the undulation. The increased
tension causes the wave to travel much faster
through the body making the wave less visible to an
observer. Since the waves travel the same distance
up or down the spine as low dynamic undulations,
the fast moving high dynamic undulations are
visible to the eye for a much shorter period of
time. Our common sense of "seeing is believing"
leads us to falsely conclude that undulations
disappear entirely during high dynamic movement.
Can a guitar string be heard long after our eyes
say it is still? This phenomenon is most notable
on the thinnest strings held with the highest
tension.
A body that allows undulation can move with high
dynamic efficiently, conserving energy by recycling
waves in 'body echos' or reflections.
Alternatively, undulations can be directed to raise
any motor-ic mass or the body in its entirety.
This transforms the kinetic energy of motion in the
wave into the potential energy stored in a risen
body. Increased tension levels in muscle groups
surrounding spine create the
metaphoric guitar string which can be tuned for fast
moving high energy waves with small amplitudes and
brief transit times. The paradox is that energy
waves become almost invisible to the human eye as the
energy of the wave packet increases, while have no waves
at all transmits zero energy along the spine.
The perceivable difference is that a no-wave-dancer generates
new movement without recycling or being informed by 'old
kinetic energy,' while the wave-dancer recycles and directs
the previously generated 'old kinetic energy.'
Any part of the body that has risen from harnessing
a wave can then fall again. This falling can be
used to create new motion in that can be
transmitted further to other parts of the body.
And so the never ending story of movement
continues, until we choose stillness or our
energies randomly scatter.
Let us briefly consider the less ideal situation
when a body moves dynamically with excess tension
in the neck, torso, and abdomen. The body will
move more like one giant block, without any
springiness. This type of movement will require
the legs and arms to push every time the body
rises, and push every time the body falls, as
momentum and energy are inefficiently conserved.
This is a body whose undulations have disappeared.
This is a dancer who is working too hard.
The highly energetic transverse waves that travel
on the ocean, known as a tsunamis, can contain
energy far exceeding any wave caused by even the
greatest of hurricanes. Tsunamis travel the ocean
at approximately 600 miles per hour (970 km per
hour) which is the same speed as airliners. When
they pass large ships or small craft on the open
ocean, there is typically a six inch (15 cm) rise
in the water level that is spread out over many
kilometers. People on board often don't know that
a powerful wave has just passed. Only when the
wave reaches shallow water does the land direct all
the kinetic energy into a tall rising of the water
just offshore. When the water can no longer
support itself, it falls forward and spills out
onto the land as a river of ocean water. All the
movement and aftermath of a tsunami comes from a
barely visible high speed wave. A similar
phenomenon occurs in and around our spine.
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