numb - Kontact Bike

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numb - Kontact Bike
If you have
never gone
numb
or cursed in
pain from
riding on a
bicycle seat,
you are
probably
lying or
don't ride
much.
Long roads often start with unemphatic
beginnings. At least that is how my journey of
studying bicycle seat design started. I was a
stressed out graduate student trying to pick a
thesis topic that would hold my interest for, at
least, the next couple of years. I have been a
die-hard cyclist since I was 12 years old, and
it was actually my mother who, after hearing
me complain about bicycle seats my entire
life, suggested I delve into the topic of bicycle
seat design. At first, I didn't take her seriously,
until I researched it further and determined
that it actually was possible. After a lot of
research, recruiting subjects, analyzing data,
and getting my research published, I was
finally finished and graduated! Other cyclists
kept asking me what I had learned, so I finally
wrote it all down in my first book on bicycle
seats, Finding the Perfect Bicycle Seat. That
book laid out much of the very detailed
scholarly research on seat design and
anatomy that I had accumulated for my
thesis. The response from readers has been
fantastic and I'm certain that it has helped
many people gain an understanding of the
science and research behind seat design.
(Even some large seat companies read the
book!)
You can't study bicycle seats for years
without developing your own ideas about an
improved design, though. Along the way, I
developed my own seat design, patented it,
sold it internationally, and was even
interviewed by major newspapers like the
New York Times and the LA Times.
I completely understand, however, that not
everyone wants to read about all of the
scientific details and research studies that
have investigated bicycle seats. Moreover,
since my first book, it seems that saddle
design has become even more “marketingdriven,” so it made sense to me to write a
new book that distills the scholarly research –
using a more graphical, easy-to-understand
approach – into a guide to help riders quickly
navigate through the large array of bicycle
seat designs and choose the best bike seat
for them based on their anatomy, riding style
and typical riding position.
Q:
BICYCLE SEATS HAVE ALWAYS
LOOKED THE SAME. SO THE
“TRADITIONAL” SEAT DESIGN
IS THE BEST, RIGHT?
Actually, bicycle
seats have come a
long way since the
earliest ancestors of
the modern bicycle.
Early devices, such
as the Draisine (circa
1817), had a simple,
upholstered saddle
area to support the rider. As bicycles
progressed to high wheelers, the seats
began to appear more triangular, though still
much wider than many modern seats.
Current research has shown that the
“traditional” bicycle seat design significantly
restricts blood flow to the rider's anatomy by
creating areas of increased pressure
without regard for which areas are able to
tolerate increased pressure and which are
too sensitive to support any of the rider's
weight. As research and understanding of
the bicycle/rider interface
expands, many new designs
have been created to fill the
performance and comfort needs of
every cyclist. There is still plenty of
room for improvement from the
traditional racing seat design that
we are all familiar with.
Many hundreds of
bicycle saddle designs have been patented
to improve comfort and decrease soreness
since the first version of the bicycle was
ridden almost 200 years ago. Today, there
remains a multitude of saddles to choose
from and a dearth of concrete information
regarding how to make the best choice for
your riding style.
Most people will tell you, “saddles are
really a personal choice” and, “one saddle
won't work for everyone.” The decision
making process is not as ambiguous as
people make it out to be, though. By
understanding the anatomy, your riding
style and typical riding position, you can
quickly narrow down
your saddle choices
to make a much
more informed
buying decision.
1
Lumbar Spine
The lower five vertebrae of the spine contribute the majority of forward flexion to the spine that allows the rider to lean forward without
rotating the pelvis on the seat. (There is normally approximately 60 degrees of forward flexion provided by the lumbar spine.) The
flexibility in this region is one predictor of how flat and aerodynamic a position the rider will be able to achieve.
2
Sacrum
The lumbar spine rests
on the sacrum, which
wedges between the
two wings of the pelvis.
The connection
between these bones
is referred to as the
sacroiliac joint, or SI
joint. There is little
movement between the
two sides of the pelvis
and the sacrum due to
many thick, fibrous
ligaments and
interlocking bone
surfaces that hold
everything closely
together in a normal,
healthy pelvis.
3
Coccyx
Connecting below the
sacrum, this vestigial
remnant of a tail is not
without function. Many
small muscles of the
pelvic floor attach to
this structure. It may
contact the seat when
riding in upright
postures.
4
Pubic
Symphysis
A dense cartilaginous
tissue that connects the
front of the two halves
of the pelvis. In men,
the pudendal nerve
and artery structures
pass beneath the pubic
symphysis as they
branch to the penile
structures.
Compression can
occur between the
pubic symphysis and
the seat when the
pelvis is rotated forward
in aerodynamic
postures.
5
Ischial
Tuberosities
The ischial tuberosities,
commonly called the “sit
bones,” are the point of
attachment for many
muscles of the lower
extremity. These muscle
forces create the wider,
flatter surface on the
bottom of the sit bones.
Although you do put
pressure on these bones
if you sit on a hard flat
surface, they really aren't
“meant” to be sat on for
long periods. The
pressure created
between the bony
prominences and the
sitting surface causes
decreased blood flow to
the soft tissues between
the two structures.
5
6
Inferior
Pubic Rami
The pubic rami form
the inferior connection
between the ischial
tuberosities and the
pubic symphysis.The
pudendal nerves,
arteries, and veins are
located along the inner
borders of the pubic
rami.
There is a lot more than just bones between your pelvis and the bicycle seat.
This region, between the pubic symphysis, sit bones, and coccyx, is referred to as
the perineum or perineal region. Large portions of the genitals are actually inside the
pelvis. Erectile tissues of the genitals, such as the corpus spongiosum in the male
and the homologous vestibular bulbs in the female, can be susceptible to pressure
from the seat. There are additional layers of adipose (fat), muscle, fascia, and skin tissues
on top of that as well.
Prolonged pressure compresses blood vessels in the skin and leads to tissue breakdown and
saddle sores. In an office chair, the sitting pressure is distributed over a much larger surface area (i.e. the
buttocks and hamstrings). Even then, everyone moves around in the chair to alternate pressure areas.
People who aren't able to move their lower body (e.g. people with paraplegia) have to consciously
remember to vary their sitting position to avoid developing pressure sores.
There are no bicycle seats that you can expect to sit on for multiple hours without shifting and
taking breaks to relieve the pressure and still be comfortable. There is simply too small asurface area and
too much weight placed on it.
Adapted from the Wikimedia Commons file
"Skin_layers.png"
Different studies have investigated sit bone distances and reported the average difference
between male and female sit bone widths is between 12mm and 18mm, depending on the study.
This relatively small margin (about a 9% difference on average) suggests that there is likely overlap
between the sexes regarding sit bone width. Women also have significantly larger and more
rounded infrapubic angles to allow for childbirth. This wider pelvic opening makes women more
susceptible to perineal pressure from narrow seats.
Although many shops purport to select your best seat by measuring your sit bone width,
Potter et al. found that the width of seat pressure spots while cycling was always smaller than the sit
bone width. (80mm vs 114mm for males in the tops position) So don't rule out seats purely on the
basis of your measured sit bone width. There's also no compelling reason for a man to avoid trying a
seat designed for a woman. Unless you simply hate the colors, the dimensions may be exactly what
you need. Finally, don't rely on any company's designation of “male” vs “female” seats. Evaluate the
dimensions yourself to determine if the seat fits your needs.
The pudendal nerves and
blood vessels that supply the
genitals can be injured by repeated
compression from the seat. In
women, these structures converge
at the clitoris. Some companies
claim that women's saddles should
have a narrower channel for
pressure relief than seats designed
for men. However, other structures
in this area, such as the vestibular
bulbs, are not designed for weightbearing, either. Therefore,both
sexes would benefit from pressure
relief throughout the perineal
region.
In both men and women, the pudendal structures run
together through a channel, termed Alcock's Canal, along
the inner borders of the inferior pubic rami. Unilateral
pressure on blood vessels might not produce immediate
discomfort, since the other side will still supply blood.
Unilateral nerve compression, though, will create
immediate discomfort or numbness. Prolonged
compression of nerve or blood vessels (bilateral or
unilateral) can lead to injury and related symptoms.
In males, the pudendal
nerves and arteries
traverse under the pubic arch as
they exit the pelvis to supply the
penis. The pubic symphysis is a
common region for the pudendal
structures to be compressed in
males, making it particularly
important not to ride on the nose of
seats that press directly into this
region.
Outside of the pelvis there
are also soft tissue structures that
contact the bicycle seat. These
include the hamstring muscle region
and the adductor muscle region (the
muscles on the inside of the thigh).
The three letters above are perhaps the most
important, and least understood, in seat design and
comfort. The amount of pressure (P) that the seat exerts
on your pelvis is equal to the amount of downward force
(F) divided by the contact surface area (A). This simple
equation has a profound impact on seat comfort.
Force can be affected by the distribution of weight
among your handlebars, pedals, and the seat. Therefore,
a rider who puts more force through the pedals and/or
bars will experience proportionally less pressure from the
seat.
Area is affected by the contact surface that the
seat provides to support your pelvis. A common approach
to seat design has been to remove large sections from
the center of the seat. But think about that in terms of the
pressure equation. Cut-out seats reduce contact area and
increase pressure on the borders of the cutout.
Depending on the width and curvature of your pelvis, this
could directly increase the pressure on the pudendal
structures.
A more sensible approach is to maintain maximal
surface area and utilize other contours of the seat, such
as depressed regions with smooth borders or flatter rear
support areas to elevate the perineum, which effectively
redistributes pressure without creating high levels of
stress on the pudendal structures.
Pressure maps
from various
studies showing
that less contact
area caused by
cut-outs can create
more pressure on
surrounding areas.
Rodano et al.
Frobose et al.
Frobose et al.
Q:
What should I look at when
choosing a seat?
Y
You probably know what size handlebar stem you need, and
you know what size tires work best for your riding style. But
what do you look for when buying a seat? Do you buy based
on the seat's looks or width alone?
It may well be impossible to suggest a particular seat for
each person reading this, since there are new models and
brands of bicycle seats coming out every year. Each person's
anatomy and biomechanics will be different as well. By having
a better understanding of what to look for when purchasing a
new seat, however, you will be able to determine which one
fits your personal riding style best, just like a set of tires.
The following is a checklist of features to consider when
comparing seat models.
Seats can range from very rounded
designs to much flatter support
surfaces that avoid pressing up in
between the sit bones, which reduces
compression on the pudendal
structures.
The seat should be fairly flat to avoid pressing up into the pelvis.
A small curvature, or rounding, may allow for the natural side-toside sway of the pelvis while riding, but the exact amount of
curvature required remains uncertain. It is more important to
avoid the central compression caused by a more tubular, or
curved, design.
Although seats with significant rear
flares were outlawed from
competition a while ago, seats still
offer a variety of side profiles. These
can serve to position the pelvis and
offer posterior support for riding on
inclines.
Many current seats offer a flatter side profile to allow the rider to
move forward and backward more easily. A dip will encourage
the rider to stay in a specific position and may act to encourage
rotation of the pelvis, which can increase pressure on the
anterior portion of the pelvis. A flatter seat is generally better if
you prefer to move forward and back frequently.
Saddles vary significantly in regard to
this curvature, depending on the
manufacturer's paradigm of where
you should sit and where the
pressure should be placed.
A gradual transition will create pressure between the rider's
thighs and encourage them to slide forward onto the nose. A
smaller angle of transition (a tighter curve between the rear
support surface and the nose) will allow the rider to remain over
the wider rear section without interfering with the pedal stroke.
This region can also press up into the perineum if it does not
offer a rear support area that is flat and wide enough to support
the sit-bone regions.
Female pelvis
Female pelvis
Hands in drops
Hands on tops
When riders adopt a more
aerodynamic posture and lean
further forward, they tend to
round their back and rotate
their hips forward. Both sexes
shift the weight away from the
sit bones and toward the pubic
rami. Men and women differ in
respect to what happens to the
pressure between their pelvis
and the seat when they shift
their hands from on top of the
bars to riding in the drops.
Women tend to create more
pressure centrally and
anteriorly. This is due, in part,
to an increased rotation of the
hips (~3o more than men), less
tissue between the pubic
symphysis and the seat, and a
wider infrapubic angle that
allows the seat to migrate
further up in between the sit
bones.
Ploeg et al.
Male pelvis
Male pelvis
Hands on tops
Hands in drops
low pressure
high pressure
F
inding the best seat style for you
depends on your riding style and
positioning on the seat. Here are
three general categories to help
you determine which seat shapes
may work for you. You can then
try various seats with the general
shapes that you are looking for to determine which
fit well and which do not.
THE UPRIGHT
RIDER
Riders who cycle in upright
positions put much less pressure
through their hands and feet than
racing cyclists. That leaves
the seat as the primary
contact point, which
creates a lot of pressure
and force on a relatively small
area. It's easy to see how a
rider in a very upright position
would want that force
distributed over the largest seat
surface possible.
The trouble with many wider seats
is that they have a gradual curvature
from the rear support surface to the
nose of the seat, which causes the
rider to move forward to reduce the material
between their thighs. (Otherwise they would feel
friction and pressure on the inner/upper thigh
tissues.) By sliding forward, however, all of the
benefits of the wider support surface are lost!
It is important to look for a seat that allows
you to remain over the rear of the seat with a nose
that does not interfere with your pedal stroke.
Many larger, recreational seats are
commonly over-padded. If the padding is too easily
deformable, it can bulge up in between the sit
bones and put pressure on the pudendal arteries
and nerves, resulting in numbness or pain. If you
can compress the padding substantially with just
your thumb, it's too soft. If you're just riding around
the block you might not notice a problem, but it will
cause discomfort over longer rides. Look for a firm
saddle with a flat rear and a narrow nose that stays
out of your thighs' way.
Noseless saddles are another option
that are available to upright riders. They
are a contentious option, though,
because they do away with the nose
entirely, which many people feel is
necessary for safe handling of the
bicycle. The upright rider pedaling
at slower speeds will have the
majority of their weight on the
seat, thus creating more contact
friction and “grip” on the seat
than a triathlete who may have the
majority of weight on the handlebars
and pedals. It is this “grip” that allows
the rider to stay in control of the
bicycle, especially around turns. I
would not recommend a
noseless seat for any type of
rider other than an upright rider.
For this type of cyclist, who also wants to
learn how to control the
bicycle without the
nose, it is an option
that can greatly reduce
pressure through the
perineal region.
Noseless bicycle seat (rear view)
THE SPORT RIDER
As a cyclist
trains to ride faster, the
rider will need to adopt
a posture to reduce wind
drag. To accomplish this,
the rider will lean forward to
reduce frontal surface area
(the amount of surface
that's exposed to
the wind) and
put more weight
on the
handlebars. They
will also pedal harder to
go faster, which takes additional
weight off of the seat. Their pelvis
will rock forward and some of the
pressure will move from the sit
bones to the pubic rami. Riders
will also be moving around a lot
more on the saddle (forward and back, on and off),
as they sprint, climb, pace-line, attack.... This is a
great thing, because it gives the arteries a chance
to recover from prolonged static sitting positions.
Casual riders or beginning sport riders aren't
able to generate as much power through the
pedals, so they tend to have more weight on the
seat, which makes them more susceptible to seatrelated issues.
This group of riders needs a firmer seat with
a nose projection to assist in controlling the bicycle,
whether they ride off-road, in packs, or quickly over
varied road surfaces that require them to be able to
correct their movement or balance at a moment's
notice.
The rear of the seat should be substantially
flat to support the pelvis without pressing between
the sit bones. The flatter the seat, the more the
perineum will be elevated above the sitting surface.
This is where the rider's preference will determine
how much pressure to put through the perineum
versus the sit bones and pubic rami. Once again, a
smaller angle of transition from the nose to the rear
support surface will allow the rider to remain over
the rear support surface more comfortably.
As discussed previously, seats with cut-outs
remove the pressure from tissues directly in
the open space, but they increase pressure
all around the border of the hole. Whether
this design is tolerable for you depends on
the alignment of your pubic bones to the borders
of the cut-out. If the seat contacts the inner
borders of the pubic rami, you will experience
greatly increased pressure on your pudendal
structures. If it hits the outside borders of
the pubic rami, it could irritate your
adductor tendons. If it contacts
you directly
Kontact © bicycle seat
on the pubic rami,
Flatter rear support elevates perineum
it could be
tolerable. A
better approach
to maintaining
maximal surface
area would be to choose
a seat with a flatter rear
support surface to elevate the
central soft tissues, as well as
the possible addition of a central
depression created
Cut-out bicycle seat
in the seat shell
Edges may press into pudendal structures
and covered
with padding,
THE TRIATHLETE
In a quest to get even more aerodynamic,
many triathletes and time trialists use aerobars and
more aggressive frame geometry (i.e.
steeper seat tube angles) that move
the rider forward in relation to the
bottom bracket. As a result, there
has been a trend in triathlon to use
seat designs that also allow the rider to
adopt a very forward position relative to
the bottom bracket.
UCI regulations
have attempted to
maintain the traditional
geometry of the bicycle
by limiting the position of the
seat in relation to the bottom bracket,
which states that the nose of the seat
needs to be at least 5cm behind the center
of the bottom bracket. Recent additions
to UCI regulations also state that the
seat be tilted no greater than 3
degrees in either direction.
Some relatively new seat designs encourage
the rider to sit farther forward on the seat. Essentially,
they remove the front of the nose of a “cut-out” seat
design and move the remaining seat geometry
forward in relation to the rails. The rider sits on the two
forward nose projections, perching on the pubic rami
while the front gap opening theoretically offers a route
for the pudendal arteries and nerves to travel without
being compressed. These “double nose” designs
offer riders the advantage of being able to sit on the
very tip of the seat. This design also greatly reduces
the contact surface area, however.
This design may be of interest to you if:
1. You require a very forward and aggressive
riding position.
2. The front projections contact you precisely at
your pubic rami. (If they press centrally, they
will put pressure on the pudendal/ perineal
structures. If they press laterally, they will put
excess pressure on the adductor tendons.)
3. You can tolerate having a reduced contact
area with the seat. This may be less of an
issue if you are able to put more pressure
through the pedals and aerobars with less
weight on the seat. Riders who sit
more upright, however, may find
that the small contact region
creates too much pressure to
remain comfortable.
Of course, this design of seat
is by no means the only option for
time trialists and triathletes. Some
seats accommodate this forward
position simply by adding more padding to
the nose of the seat. The padding
contours to the body and provides more
comfort than a standard hard seat
nose, albeit while providing less
contact surface than the rear of the
seat.
Another option is to modify the fit of the bike
to allow the rider to remain over the wider, rear
portion of the saddle while in the aerobar position.
This may not be as aggressive a position as the
other option, but the
aerodynamics of the
Dual-nose bicycle seat
forward position
must always be
balanced against
the rider's ability
to maximize power
output, tolerate the
position, and maintain
enough chest excursion/
respiration to maintain their
maximal power output (and
comfort!) over the duration of the
event. For the majority of recreational riders, it's
probably a good idea to maximize seat contact
surface to avoid seat-related issues.
Q:
DOES HAMSTRING LENGTH
EFFECT MY SADDLE CHOICE?
A: Not really, according to a study out of the
Department of Biomedical Engineering,
University of Wisconsin-Madison.
They found that the differences in
pelvic motion could not be explained by
either ischial tuberosity width
or hamstring flexibility. They
reported that flexibility in the
lumbar spine was the
strongest determinant of
anterior pelvic tilt during
cycling.
Q:
WHAT ABOUT THE PROS? HOW
DO THEY AVOID ALL THESE
ISSUES?
A: As mentioned earlier, pros probably put
less pressure through the saddle because
of increased power output and a more
aggressive riding position that transitions
more force toward the bars and pedals.
That does not mean that
they are immune to saddlerelated issues, however!
Many pro riders have
actually had to drop out of
major races because of
saddle sores. In 1976, the
great Eddy Merckx could
not even begin the Tour de
France, despite having a very strong early
season, because of saddle sores (which
later required surgery). And it's not only
Merckx; Laurent Fignon, Greg Lemond, and
even Lance Armstrong were all hindered by
the pain of seat-related issues during their
careers.
If you want to
get more
aerodynamic,
take a look at
If you have a tight lower your low back
back, you will tend to roll your flexibility.
hips further forward to
compensate (putting more pressure onto
your pubic rami). If you have a very flexible
lower back, you will tend to sit with your
pelvis more upright (on the sit bones).
This preference towards a more
upright pelvic posture may have been
correlated with the design of the seat, but
this was not addressed in the study - they
used a traditional seat design. They also
studied a younger age group of students
who, most likely, did not suffer from severe
hamstring tightness issues.
Therefore, if you want to get more
aerodynamic, take a look at your low back
flexibility. (This doesn't mean that overly
tight hamstrings won't affect your riding,
though!)
Unfortunately, professional riders usually
aren't even able to choose their own seats
due to sponsorship issues. So when pros
develop saddle sores or seat-related issues,
they deal with them the same way everyone
else does - maybe with a little more grit and
determination, but they use the same tricks.
it. It's better to take a week off now
rather than a month off because you
avoided dealing with it and it
worsened.
Seat Safety Tips
• Wear proper fitting shorts that do not
bunch up while riding.
• Use padded shorts that do not have
seams at seat contact areas. (Thicker
is not necessarily better.)
• Do not wear underwear. (It can
increase moisture against the skin,
increase friction, and create seams at
seat contact points that cause
irritation.) If you need an extra barrier
to the weather or to add padding to
un-padded shorts/tights, there is
cycling-specific underwear available.
• Make sure your bicycle fits correctly
so that you can sit on your seat
correctly and comfortably.
• Use a lubricant to reduce high friction
areas.
• Always wear clean shorts to prevent
bacterial buildup.
• Get out of your shorts and get dry
immediately after you finish riding.
• Move around on the seat and get out
of your seat while riding – at least
every 10 minutes.
• Switch between seats. If you REALLY
must continue riding, you could try
swapping out to a different seat that
contacts you at different points.
• Use a supportive and well-designed
seat.
•
Treat sores early on! If you
experience a blistering/ pimple like
area/ sore region, take the time to
let it heal before it gets out of hand.
For minor sores, you can simply
take some time off of the bicycle and
allow it to heal. If it doesn't improve,
consult your doctor and do not ignore
•
Always stand up out of the seat when
riding over rail-road tracks and other
jarring terrain.
Q:
How should I care for my bicycle
seat?
A: Clean your seat regularly using water
and neutral soap to remove grease and dirt
if needed. Avoid petrol-based solutions and
solvents. Also avoid using high-pressure
washers to clean the seat, since it could
damage the surface and gluing. It's also
recommended to use room-temperature
water to avoid damaging the seat's
materials. Most seats with plastic/composite
shells can be cleaned in this manner.
If you choose to ride a tensioned
leather seat (ex. Brooks), there are some
good suggestions for proper care on the
Brooks website as well as Sheldon Brown's
website.
If you take the time to understand
your anatomy and biomechanics, and
thoughtfully narrow down your seat
choices, it will help you to continue to
enjoy cycling with a better chance of
avoiding seat issues and instead ride in
relative comfort.
A C K N O W L E D G E M E N T S
Wonderful Open Source programs
that made these graphics possible:
Blender
GNU Image Manipulation Program (GIMP)
Inkscape
Sources of motivation and support
that ensured the completion of this guide:
Shani Cohen
John Marsh
Milo

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