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SEXOL-858;
No.
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Pages
7
Sexologies
xxx
(xxxx)
xxx.e1—xxx.e7
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en
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sur
ScienceDirect
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RESEARCH
IN
ACTION
Coital
positions
and
clitoral
blood
flow:
A
biomechanical
and
sonographic
analysis
K.
Lovie ∗,
A.
Marashi
Department
of
medical
imaging
and
AI,
New
H
Medical,
PC,
176
Johnson
Street
#6H
Brooklyn,
11201
New
York,
United
States
KEYWORDS
Clitoris;
Biomechanics;
Sexual
positions;
Sonography
Summary
Objective.
—
To
create
biomechanical
models
of
five
common
coital
positions,
and
evaluate
the
degree
of
contact
and
forces
against
the
clitoris.
To
evaluate
clitoral
blood
flow
before
and
after
engaging
in
these
positions.
Methods.
—
Biomechanical
models
were
rendered
of
a
male
and
female
pelvis
in
the
follow-
ing
coital
positions:
face-to-face/female
above,
sitting/face-to-face,
face-to-face/male
above
(with
and
without
pillow),
and
kneeling/rear
entry.
The
thrusting
force
and
gravitational
force
were
estimated
for
the
pelvis(es)
providing
the
main
forces.
The
areas
of
contact
between
the
pelvises
were
identified
and
highlighted.
Sonography
of
the
clitoris
was
performed
before
and
after
a
healthy
volunteer
couple
engaged
in
each
position,
using
a
Philips
LumifyTM ultra-
sound
(Koninklijke
Philips
N.V.,
Amsterdam,
Netherlands)
with
a
L12-4
linear
array
transducer
(4—12
MHz).
Results.
—
The
biomechanical
models
for
each
position,
with
the
exception
of
kneeling/rear
entry,
reveal
a
large
amount
of
contact
with
the
clitoris.
Clitoral
blood
flow
increased
after
engaging
in
each
position
except
for
kneeling/rear
entry.
Positions
in
which
the
gravitational
force
of
the
thrusting
partner
was
in
the
same
direction
of
(and
thereby
augmenting)
the
thrusting
force
resulted
in
intense
clitoral
blood
flow
(face-to-face/female
above,
and
face-to-
face/male
above).
Augmenting
the
face-to-face/male
above
position
with
a
pillow
generated
a
component
of
the
male
pelvic
gravitational
force
in
the
direction
of
the
clitoris;
this
resulted
in
more
blood
flow
to
all
components
of
the
cavernous
body.
Conclusion.
—
From
a
biomechanical
perspective,
different
coital
positions
vary
in
their
poten-
tial
to
stimulate
the
clitoris.
These
positions
lead
to
variable
increases
in
clitoral
blood
flow,
concordant
with
our
biomechanical
models.
©
2022
Sexologies.
Published
by
Elsevier
Masson
SAS.
All
rights
reserved.
∗Corresponding
author
at:
469
West
57
Street,
#3C,
10019
New
York,
NY,
United
States.
E-mail
address:
kimberly.lovie@nycgyno.com
(K.
Lovie).
https://doi.org/10.1016/j.sexol.2022.04.007
1158-1360/©
2022
Sexologies.
Published
by
Elsevier
Masson
SAS.
All
rights
reserved.
Please
cite
this
article
as:
K.
Lovie
and
A.
Marashi,
Coital
positions
and
clitoral
blood
flow:
A
biomechanical
and
sono-
graphic
analysis,
Sexologies,
https://doi.org/10.1016/j.sexol.2022.04.007
ARTICLE IN PRESS
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SEXOL-858;
No.
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Pages
7
K.
Lovie
and
A.
Marashi
Introduction
The
purported
benefits
of
various
coital
positions
are
described
in
numerous
magazines,
books,
and
public
forums.
However,
there
is
little
scientific
research
that
evaluates
the
association
between
different
coital
positions
and
their
abil-
ity
to
produce
female
orgasm.
A
survey
of
Swedish
women
evaluated
the
tendency
of
various
sexual
techniques
(but
not
positions)
to
cause
climax.
In
this
study,
51—57%
of
women
achieved
orgasm
though
penile
penetration
alone,
and
50%
through
clitoral
stimulation
alone
(Fugl-Meyer
et
al.,
2006).
Swieczkowski
and
Walker
evaluated
the
ability
of
different
coital
positions
to
produce
orgasm
by
adminis-
tering
a
questionnaire
with
a
40-point
Likert
scale
(ranging
from
0/‘‘not
at
all’’
to
40/‘‘exclusively’’).
The
average
ratings,
in
order
of
decreasing
orgasm
potential,
were:
face-to-face/male
above
(28),
face-to-face/female
above
(26.36),
manipulation
of
female
genitals
by
partner
(23.47),
cunnilingus
(17.94),
face-to-face/side
position
(16.73),
stimulation
of
breasts
and
other
non-genital
areas
(11.69),
sitting/face-to-face
(10.78),
prone/rear
entry
(8.23),
kneel-
ing/rear
entry
(5.85),
sitting/rear
entry
(3.81),
stimulation
by
vibrator
(2.26),
and
anal
intercourse
(0.89)
(Swieczkowski
and
Walker,
1978).
In
2018,
Krejcová
et
al.
investigated
coital
positions
in
a
group
of
Czech
volunteers.
Participants
were
shown
a
series
of
black
and
white
drawings
of
13
sexual
posi-
tions
and
were
asked
to
estimate
what
percentage
of
the
time
they
led
to
orgasm;
9
positions
were
coital:
face
to
face/male
above,
prone/rear
entry,
standing/face-to-face,
standing,
face-to-face/female
above,
supine/female
above,
kneeling/rear
entry,
sitting/face-to-face,
and
standing/rear
entry.
The
most
common
positions
(over
participants’
life-
times,
and
within
the
past
5
years)
were:
face
to
face/male
above
(median
80%
for
females),
face-to-face/female
above
(median
40%
for
females),
and
kneeling/rear
entry
(median
42%
for
women).
The
face
to
face/female
above
and
sitting/face-to-face
positions
were
most
likely
to
result
in
orgasm,
while
the
kneeling/rear
entry
position
was
least
likely
(Krejcová
et
al.,
2020).
Krejcová
et
al.
attribute
the
success
of
face-to-face
positions
to
their
ability
to
facilitate
communication,
both
verbal
and
physical
(Krejcová
et
al.,
2020).
Although
these
psychological
factors
are
involved
in
orgasm
(Meston
et
al.,
2004;
Brody,
2010;
Brody
and
Costa,
2017;
Adam
et
al.,
2020),
physical
stimulation
of
the
clitoris,
which
has
been
recognized
as
‘‘possibly
the
most
critical
organ
for
female
sexual
health,’’
likely
plays
a
dominant
role
(Mazloomdoost
and
Pauls,
2015).
Female
orgasm
is
hypothesized
to
be
regu-
lated
by
both
autonomic
and
somatic
nerves,
and
involves
a
complex
reflex
arc.
According
to
O’Connell
et
al.
(O’Connell
et
al.,
2005)
this
process
probably
involves:
•
Receptors
within
the
clitoris
and
vulva
detecting
stimulus
(i.e.
touch);
•
somatic
afferents
of
the
pudendal
nerve
(dorsal
clitoral
and
perineal
branches);
•
S2-4
spinal
cord
levels
transmitting
information
to
the
brain;
•
visceral
efferents
of
the
pelvic
splanchnic
nerves;
•
parasympathetic
stimulation
of
the
clitoris
resulting
in
dilation
of
the
of
the
clitoral
arteries;
•
erectile
tissue
of
the
clitoris
becoming
engorged
with
blood
(increased
inflow
and
decreased
outflow
of
blood);
•
secretions
from
the
Bartholin
and/or
Skene
glands
and
urethra;
•
sympathetic
stimulation
of
the
urovaginal
plexus
(through
the
hypogastric
nerves
and
inferior
hypogastric
plexus);
•
skeletal
muscle
contraction
of
the
vagina,
anus,
and
ure-
thra
(through
the
pudendal
nerve).
From
a
biomechanical
perspective,
pelvic
floor
mus-
cles
are
also
crucial
to
orgasm,
with
stronger
pelvic
floor
muscles
associated
with
improved
sexual
function
(Kanter
et
al.,
2015;
Kegel,
1952;
Graber
and
Kline-Graber,
1979;
Lowenstein
et
al.,
2010;
Martinez
et
al.,
2014).
Although
other
biomechanical
factors
(i.e.
forces
against
the
cli-
toris)
likely
play
a
major
role
in
this
process,
female
orgasm
has
yet
to
be
formally
studied
from
this
perspec-
tive.
Researchers
generally
agree
that
there
is
a
distinction
between
orgasms
resulting
from
clitoral
stimulation,
or
‘‘clitoral
orgasm’’
(CO),
and
those
resulting
from
vaginal
penetration
without
clitoral
stimulation,
or
‘‘vaginally
acti-
vated
orgasm’’
(VAO)
(Jannini
et
al.,
2012;
Buisson
and
Jannini,
2013).
A
VAO
is
hypothesized
to
involve
stimula-
tion
of
the
clitorourethrovaginal
(CUV)
complex
(Jannini
et
al.,
2012;
Buisson
and
Jannini,
2013).
Buisson
and
Jannini
performed
a
sonographic
study
to
evaluate
clitoral
blood
flow
after
external
and
internal
stimulation
(Buisson
and
Jannini,
2013).
Additional
sonographic
studies
have
evalu-
ated
the
CUV
complex
(Buisson
et
al.,
2008;
Gravina
et
al.,
2008;
Foldes
and
Buisson,
2009;
Battaglia
et
al.,
2009;
Battaglia
et
al.,
2010a;
Battaglia
et
al.,
2010b).
However,
no
sonographic
studies
have
been
performed
to
evaluate
the
efficacy
of
different
coital
positions.
Materials/Patients
We
evaluated
different
common
coital
positions
and
their
ability
to
stimulate
areas
in
the
female
pelvis
that
are
involved
in
orgasm,
with
attention
to
the
clitoris.
The
fol-
lowing
five
positions
were
assessed:
face-to-face/female
above,
sitting/face-to-face,
face-to-face/male
above
(with
and
without
pillow),
and
kneeling/rear
entry.
These
five
positions
were
chosen
because
they
were
among
the
most
or
least
likely
to
cause
orgasm,
or
were
the
most
com-
mon
based
on
the
results
of
Krejcová
et
al.
(Krejcová
et
al.,
2020)
In
their
study,
the
face-to-face/female
above
and
sitting/face-to-face
positions
were
most
likely
to
cause
orgasm.
The
kneeling/rear
entry
position
was
least
likely
to
cause
orgasm.
The
face-to-face/male
above
position
was
evaluated
because
it
was
the
most
common
(Krejcová
et
al.,
2020).
We
also
evaluated
the
face-to-face/male
above
posi-
tion
with
a
pillow
because
it
is
a
common
coital
practice.
The
five
positions
were
performed
by
a
healthy
medi-
cal
doctor
couple,
both
32-years-old,
at
home.
Given
the
sensitive
nature
of
the
research,
the
participants
were
cho-
sen
because
they
were
well-known
to
the
researchers,
and
willingly
volunteered
for
the
study.
The
participants
were
in
a
monogamous
relationship
with
each
other.
Both
partici-
pants
were
healthy
and
had
no
sexually
transmitted
illnesses
xxx.e2
ARTICLE IN PRESS
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SEXOL-858;
No.
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7
Sexologies
xxx
(xxxx)
xxx.e1—xxx.e7
or
significant
past
medical
history.
They
completed
the
Ari-
zona
Sexual
Experiences
Scale
(ASEX)
and
the
short
form
of
the
Female
Sexual
Function
Index
(FSFI-6),
two
validated
tools
for
evaluating
for
sexual
dysfunction;
neither
volunteer
had
sexual
dysfunction.
Informed
consent
was
obtained
for
both
participants.
This
study
was
carried
out
in
accordance
with
The
Code
of
Ethics
of
the
World
Medical
Association
(Declaration
of
Helsinki).
Methods
Biomechanical
anatomical
drawings
of
a
generic
male
and
female
pelvis
were
rendered
in
the
five
positions
using
Adobe
PhotoshopTM software.
The
male
pelvis
and
penis
were
depicted
with
decreased
opacification
to
better
visu-
alize
the
clitoris
and
vagina.
Areas
of
contact
between
the
female
vulva,
vagina,
and
her
partner’s
skin
and
penis
were
rendered
in
pink.
The
dominant
forces
involved
in
each
coital
position
were
depicted
with
vector
arrows.
Of
note,
the
magnitudes
of
the
vectors
were
chosen
arbitrarily,
as
they
depend
on
participant
mass
and
thrusting
forces
(which
are
partner-dependent).
The
gravitational
forceat
the
pelvic
center
of
mass
was
depicted
for
the
pelvis
that
provided
the
thrusting
force;
this
allowed
us
to
evaluate
whether
grav-
ity
(or
its
resolved
components)
added
to
the
overall
force
directed
against
the
clitoris.
The
location
of
the
center
of
gravity
was
estimated
based
on
data
from
the
Human
Per-
formance
Lab
(Cincinnati
Children’s
Hospital)
(Body
Center
of
Mass,
2022).
The
five
positions
were
evaluated
in
the
volunteer
cou-
ple.
The
duration
of
each
position
was
10
minutes.
The
objective
was
to
compare
clitoral
blood
flow
before
and
after
coitus
in
each
of
the
five
positions,
after
a
stan-
dardized
period
of
time.
Although
it
was
not
necessary
to
achieve
orgasm,
it
was
recorded
if
it
occurred.
Clitoral
ultrasound
was
performed,
with
grayscale
and
color
Doppler
ultrasound
images
obtained
before
and
after
coitus,
in
the
coronal
and
sagittal
planes.
Ultrasound
was
chosen
as
the
imaging
modality,
as
it
is
an
efficient,
low-cost
method
to
evaluate
the
clitoris,
and
can
be
performed
in
any
setting
(i.e.
at
home).
Greyscale
ultrasound
images
(not
evaluating
blood
flow)
were
acquired
to
assess
clitoral
anatomy.
Color
Doppler
ultrasound
images
were
obtained
to
evaluate
blood
flow
before
and
after
clitoral
stimulation.
The
ultrasound
images
were
obtained
with
a
Philips
LumifyTM ultrasound
machine
and
L12-4
linear
array
(4—12
MhHz)
transducer.
Cli-
toral
blood
flow
was
assessed
qualitatively
with
a
uniform
gain
setting
for
all
Doppler
acquisitions.
A
uniform
light
pres-
sure
was
applied
with
the
transducer,
acknowledging
that
heavier
pressure
could
skew
blood
flow.
Each
coital
position
was
evaluated
on
a
different
day
to
allow
the
clitoral
blood
flow
to
return
to
baseline.
This
ensured
that
the
order
in
which
the
coital
positions
was
evaluated
did
not
influence
the
results.
Results
The
ultrasound
acquisitions
in
the
transverse
plane
reveal
paired,
hypoechoic
cavernous
bodies
on
either
side
of
the
urethra.
In
the
sagittal
image,
the
glans,
raphe,
and
body
of
the
cavernous
body
are
visualized.
The
ischiopubic
ramus
is
adjacent
to
the
cavernous
body.
The
vestibular
bulbs
are
on
a
more
medial
plane
than
the
cavernous
bodies,
and
are
not
seen
in
the
sagittal
image
(Fig.
1).
The
biomechanical
models
for
each
position,
with
the
exception
of
the
kneeling/rear
entry
position,
reveal
a
large
amount
of
contact
between
the
female’s
clitoris
and
her
partner’s
skin.
In
the
biomechanical
model
for
the
face-to-face/female
above
position,
the
gravitational
force
at
the
female
pelvis
center
of
mass
is
in
the
same
direction
as
the
female
thrust-
ing
force
(Fig.
2a).
This
resulted
in
intense,
symmetric
blood
flow
to
all
three
parts
of
the
cavernous
bodies:
the
medial
aspect
of
the
body
and
raphe,
and
the
proximal
aspect
of
the
glans
(Fig.
2).
For
the
sitting/face-to-face
position,
both
partners
pro-
vide
a
thrusting
force
in
opposite
directions.
The
location
of
the
center
of
gravity
for
the
male
and
female
pelvis
are
approximately
in
the
same
location
between
the
partners.
This
gravitational
force
is
perpendicular
to
both
thrusting
force
vectors
(Fig.
3a).
This
position
led
to
a
relatively
small,
symmetric
increase
in
blood
flow,
localized
to
the
medial
aspect
of
the
cavernous
bodies
(Fig.
3).
In
the
face-to-face/male
above
position,
the
gravita-
tional
force
of
the
male
pelvis
is
almost
perpendicular
to
his
thrusting
force
(Fig.
4a).
This
led
to
an
intense,
diffuse
increase
in
blood
flow
to
all
aspects
of
the
cavernous
bodies,
and
to
the
surrounding
pelvic
tissues
(Fig.
4).
Modifying
the
face-to-face/male
above
position
with
a
pillow
can
be
mod-
eled
with
the
male
and
female
pelvises
on
an
inclined
plane.
The
force
of
gravity
from
the
male
pelvis
(Fg)
is
resolved
into
two
components:
the
gravitational
force
perpendicular
to
the
inclined
plane
(F⊥),
and
the
gravitational
force
parallel
to
the
plane
(F//)
(Fig.
5a).
This
led
to
an
intense,
symmet-
ric
blood
flow
to
the
body
and
raphe
of
the
cavernous
body
(Fig.
5).
The
biomechanical
model
for
the
kneeling/rear
entry
position
reveals
minimal
contact
between
the
female’s
clitoris
and
her
partner’s
skin.
The
male
thrusting
force
is
perpendicular
to
the
gravitational
force
at
the
female
pelvis’
center
of
gravity
(Fig.
6a).
This
resulted
in
a
neg-
ligible
increase
in
blood
flow
(Fig.
6).
The
male
and
female
volunteers
achieved
orgasm
during
all
five
sessions.
Discussion
The
biomechanical
models
of
the
face-to-face
positions
(including
face-to-face/female
above,
face-to-face/male
above
with
and
without
pillow,
and
sitting/face-to-face)
demonstrate
a
considerable
amount
of
contact
between
the
female
pelvis
and
her
partner’s
skin.
Although
Krejcová
et
al.
attribute
the
success
of
the
face-to-face
positions
to
their
ability
to
facilitate
verbal
and
physical
commu-
nication
(Krejcová
et
al.,
2020),
our
models
support
our
hypothesis
that
face-to-face
positions
also
maximize
cli-
toral
stimulation
and
increase
blood
flow.
The
kneeling/rear
entry
position
produces
the
least
amount
of
direct
clitoral
contact,
and
resulted
in
a
negligible
increase
in
blood
flow
compared
to
the
face-to-face
positions.
According
to
Krejcová
et
al.,
the
face-to-face/female
above
position
was
among
the
most
likely
to
lead
to
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Figure
1
Transverse
(a)
and
sagittal
(b)
views
of
the
clitoris
depicting
the
paired
cavernous
bodies
(CB)
urethra
(Ure),
glans
(GL),
raphe
(RA),
ischiopubic
ramus
(IR),
and
vagina
(VA).
Figure
2
Biomechanical
model
of
the
face-to-face/female
above
position.
The
thrusting
force
(FT)
is
provided
by
the
female
pelvis,
and
is
in
the
same
direction
as
the
gravitational
force
(Fg)
at
the
female
pelvis
center
of
mass
(a).
Transverse
and
sagittal
views
of
the
clitoris
before
(b
and
c)
and
after
(d
and
e)
engaging
in
the
face-to-face/female
above
position,
with
color
Doppler
flow.
Figure
3
Biomechanical
model
of
the
sitting/face-to-face
position
(a).
Both
partners
apply
a
thrusting
force
(FT)
in
opposite
directions,
which
are
both
perpendicular
to
the
female
and
male
pelvis
gravitational
force
(Fg).
Transverse
and
sagittal
views
of
the
clitoris
before
(b
and
c)
and
after
(d
and
e)
engaging
in
the
sitting/face-to-face
position,
with
color
Doppler
flow.
orgasm
(Krejcová
et
al.,
2020).
Based
on
the
biomechanical
model,
with
the
female
positioned
above,
the
downward
force
of
gravity
maximizes
the
pressure
on
the
clitoris.
This
gravitational
force
is
also
in
the
same
direction
as
the
female
thrusting
force,
which
can
help
facilitate
this
motion.
Additionally,
compared
to
when
she
is
below
her
partner,
she
has
more
control
over
the
pressure
exerted
against
the
clitoris.
Although
this
position
did
not
lead
to
the
largest
increase
in
blood
flow,
it
was
the
only
posi-
tion
in
which
all
aspects
of
the
cavernous
body
were
involved.
Krejcová
et
al.
found
that
the
sitting/face-to-face
posi-
tion
had
a
high
likelihood
of
causing
orgasm
(Krejcová
et
al.,
2020),
which
is
supported
by
our
model.
This
position
allows
each
partner
equal
opportunity
to
exert
a
thrusting
force
against
the
other,
which
can
increase
the
pressure
against
the
clitoris.
Of
note,
the
gravitational
force
is
perpendicular
to
both
partners’
thrusting
forces,
and
does
not
contribute
to
the
total
force
(and
therefore
pressure)
exerted
against
the
clitoris.
These
biomechanical
factors
might
explain
why
the
sitting/face-to-face
position
has
a
high
likelihood
of
causing
climax,
but
is
not
the
most
likely.
These
findings
are
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Figure
4
Biomechanical
model
of
the
face-to-face/male
above
position
(a).
The
thrusting
force
(FT)
is
provided
by
the
male
pelvis,
and
is
approximately
perpendicular
to
the
gravitational
force
of
the
male
pelvis
(Fg).
Transverse
and
sagittal
views
of
the
clitoris
before
(b
and
c)
and
after
(d
and
e)
engaging
in
the
face-to-face/male
above
position,
with
color
Doppler
flow.
Figure
5
Biomechanical
model
of
the
face-to-face/male
above
with
a
pillow
(a).
The
thrusting
force
(FT)
is
provided
by
the
male
pelvis.
The
force
of
gravity
from
the
male
pelvis
(Fg)
is
resolved
into
two
components:
the
gravitational
force
perpendicular
to
the
inclined
plane
(F⊥),
and
the
gravitational
force
parallel
to
the
plane
(F//).
Transverse
and
sagittal
views
of
the
clitoris
before
(b
and
c)
and
after
(d
and
e)
engaging
in
the
face-to-face/male
above
position
with
pillow,
with
color
Doppler
flow.
Figure
6
Biomechanical
model
of
the
kneeling/rear
entry
position
(a).
The
thrusting
force
(FT)
is
provided
by
the
male
pelvis,
and
is
approximately
perpendicular
to
the
gravitational
force
of
the
male
pelvis
(Fg).
Transverse
and
sagittal
views
of
the
clitoris
before
(b
and
c)
and
after
(d
and
e)
engaging
in
the
kneeling/rear
entry
position.
corroborated
by
ultrasound:
the
sitting/face-to-face
posi-
tion
resulted
in
increased
blood
flow
compared
to
baseline,
but
less
than
the
positions
in
which
pelvic
gravitational
force
is
exerted
against
the
clitoris.
The
face-to-face/male
above
position
(without
a
pillow)
was
the
most
common
position
reported
by
Krejcová
et
al.
(median
80%
for
females).
However,
it
was
not
among
the
positions
most
likely
to
lead
to
orgasm
(Krejcová
et
al.,
2020).
This
finding
might
be
explained
by
the
woman
hav-
ing
less
control
over
the
pressure
exerted
against
the
vulva.
Interestingly,
this
position
led
to
the
largest
increase
in
blood
flow
to
the
clitoris
and
surrounding
tissues,
which
was
diffuse.
A
variation
of
this
position
involves
the
woman
tilting
her
pelvis
upwards,
sometimes
with
the
aid
of
a
pil-
low.
Pillows
marketed
for
this
intention,
often
referred
to
as
‘‘sex
pillows,’’
or
‘‘positioning
pillows’’
are
usually
firm
and
wedged
shaped,
providing
more
precise
and
consistent
pelvic
angulation
than
conventional
bed
pillows.
Although
Krejcová
et
al.
did
not
evaluate
the
frequency
of
orgasm
when
a
pillow
was
used
in
this
position,
the
biomechanical
models
suggest
that
a
pillow
would
increase
the
likelihood
of
orgasm:
a
female
can
adjust
herself
on
the
pillow
to
increase
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K.
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Marashi
the
amount
of
contact
between
the
clitoris
and
her
partner’s
skin.
The
F//component
of
gravity
created
by
the
‘‘inclined
plane’’
of
the
pillow
allows
more
force
(and
therefore
pres-
sure)
to
be
directed
from
the
male
pelvis
to
the
clitoris.
In
addition
to
increasing
the
amount
of
contact
and
pressure
on
the
clitoris,
pillows
can
increase
the
depth
of
penetra-
tion.
Of
note,
the
participants
studied
by
Krejcová
et
al.
rated
positions
with
deep
vaginal
penetration
as
more
plea-
surable
(Krejcová
et
al.,
2020).
In
our
volunteer
couple,
this
position
resulted
in
an
intense,
symmetric
increase
in
blood
flow
to
the
clitoris,
less
diffuse
than
when
a
pillow
was
not
used.
Krejcová
et
al.
found
that
the
median
frequency
of
the
kneeling/rear
entry
position
was
among
the
least
likely
to
result
in
orgasm
(Krejcová
et
al.,
2020).
Because
the
penis
spans
the
posterior
aspect
of
the
perineum
to
enter
the
vagina,
this
position
might
result
in
decreased
contact
with
the
clitoral
bulbs,
therefore
making
orgasm
less
likely.
This
was
supported
by
our
biomechanical
model,
which
demon-
strates
the
least
clitoral
contact
compared
to
the
other
positions
studied.
This
led
to
a
minimal
increase
in
clitoral
blood
flow.
Our
study
was
limited
to
creating
biomechanical
models
for
five
coital
positions,
and
evaluating
changes
in
clitoral
blood
flow
in
one
female
volunteer
after
engaging
in
these
positions.
Individual
women
might
have
different
respon-
siveness
to
stimulation
from
these
positions.
Additionally,
different
partners
might
exert
varying
degrees
of
thrusting
forces,
which
would
impact
the
predictions
of
the
biome-
chanical
models.
Psychological
factors
also
play
a
role
in
clitoral
blood
flow
and
orgasm,
and
are
not
accounted
for
in
this
investigation
(Meston
et
al.,
2004;
Brody,
2010;
Brody
and
Costa,
2017).
Since
this
is
a
pilot
study,
it
is
important
that
it
be
replicated
with
a
larger
number
of
subjects.
Conclusions
Our
findings
suggest
that,
from
a
biomechanical
perspective,
different
coital
positions
vary
in
their
potential
to
stimu-
late
the
clitoris.
These
positions
lead
to
variable
increases
in
clitoral
blood
flow,
concordant
with
our
biomechani-
cal
models.
According
to
our
results,
face-to-face
positions
are
more
likely
to
lead
to
orgasm
because
they
maximize
clitoral
stimulation
and
blood
flow.
In
addition,
positions
in
which
the
female
partner
has
more
control
over
the
pressure
exerted
on
the
clitoris
(i.e.
female
above)
pro-
duce
more
uniform
increases
in
clitoral
blood
flow.
These
results
can
help
clinicians
inform
patients
with
sexual
dys-
function.
Difficulty
achieving
orgasm,
the
causes
of
which
are
multifactorial,
is
one
component
of
sexual
dysfunc-
tion.
Clinicians
can
use
these
findings
to
counsel
patients
about
which
coital
positions
might
help
them
achieve
climax.
Disclosure
of
interest
The
authors
declare
that
they
have
no
competing
interest.
Acknowledgements
We
thank
Dr.
Nima
Nouri
Naini
for
his
support
and
help-
ful
radiology
discussions
from
the
beginning
of
our
research
endeavors.
We
thank
Claire
Chanu
for
assistance
with
French
translation.
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