The Effects of Gravity Inversion Procedures on Systemic Blood Pressure: Intra-ocular Pressure, and Central Retinal Arterial Pressure.

Abstract

Gravity Inversion Boots (a device which clasps around the ankle joint and hooks onto a stationary horizontal bar allowing one to hang stationary in an inverted, head down position) is a popular method for traction and exercise now being used by an estimated one million people. Recent reports in the medical literature suggests that this device may be contraindicated in patients with hypertension, cardiovascular disease, and ocular problems. In an effort to document physiologic changes which occur in the inverted position, twenty healthy medical students were subjected to a 3-minute inactive period of inversion. Systemic blood pressure, pulse rates, central retinal arterial pressure, and intraocular pressures were measured and found to be significantly elevated in all subjects. We speculate that this device may be contraindicated in certain patient populations, specifically hypertensives. Caution is advised in relation to people with spinal instability, suspected abnormalities in hemostasis, or with intraocular hypertension.

Full text

The
effects
of
gravity
inversion
procedures
on
systemic
blood
pressure,
intraocular
pressure,
and
central
retinal
arterial
pressure
RONALD
M.
KLATZ,
D.O.
ROBERT
M.
GOLDMAN,
B.S.
BURTON G. PINCHUK, o.D.
KENNETH
E. NELSON,
D.O.
ROBERTS. TARR,
PH
.D.
Chicago, Illinois
Gravity
Inversion
Boots
(a
device
which
clasps
around
the
ankle
joint
and
hooks
onto
a
stationary
horizontal
bar
allowing
one
to
hang
stationary
in
an
inverted,
head
down
position)
is
a
popular
method
for
traction
and
exercise
now
being
used
by
an
estimated
one
million
people.
Recent
reports
in
the
medical
literature
suggest
that
this
device
may
be
contraindicated
in
patients
with
hypertension,
cardiovascular
disease,
and
ocular
problems.
In
an
effort
to
document
physiologic
changes
which
occur
in
the
inverted
position,
twenty
healthy
medical
students
were
subjected
to
a
3-minute
inactive
period
of
inversion.
Systemic
blood
pressure,
pulse
rates,
central
retinal
arterial
pressure,
and
intraocular
pressures
were
measured
and
found
to
be
significantly
elevated
in
all
subjects.
We
speculate
that
this
device
may
be
contraindicated
in
certain
patient
populations,
specifically
hypertensives.
Caution
is
advised
in
relation
to
people
with
spinal
instability,
suspected
abnormalities
in
hemostasis,
or
with
intraocular
hypertension.
Gravity
inversion
boots
are
devices
that
clasp
around
the
ankle
joint
and
permit
an
individual
to
hang
from a
stationary
horizontal
bar
in
a totally
inverted
(
-90
°
head
down)
position.
Inversion
boots were first designed by Martin,
1
a California
Effects of gravity inversion procedures
orthopedic surgeon,
as
a traction device to relieve
interspinal
disk
pressures
.
The
boots
allow
the
participant
to
utilize
gravity
and
one
's
body
weight to decompress
the
spine. Since
their
devel-
opment
in
the
late
1960s,
gravity
inversion boots
have
enjoyed widespread use, including
many
un-
likely applications such
as
weight lifting while
in
the
inverted
position.
1·4
The
manufacturers
have
attempted
to
inform
potential
purchasers
about
the
contraindications
to
gravity
inversion therapy: uncompensated con-
gestive
heart
failure, uncontrolled hypertension,
carotid
artery
stenosis,
and
hiatal
hernia.
6
There
have been reports of individuals suffering perior-
bital
petechiae,
5
headaches,
and
sensations
of
head
pressure.
6
A review of
the
medical
and
aerospace
literature
yielded
little
information on
the
effects of
total
in-
version. According to estimates from
the
various
manufacturers'
data,
as
many
as
one
million
Americans
may
be
engaging
in
this
activity.
Therefore, we
thought
it
important
to study
the
ef-
fects of inversion on systemic blood pressure, pulse
rate,
central
retinal
arterial
pressure,
and
intra-
ocular pressure.
Materials
and
methods
Eighteen
male
and
two female subjects,
ranging
in
age from 22 to 33 years, were chosen from
the
stu-
dent
body of
the
Chicago College of
Osteopathic
Medicine. The volunteers
had
no medical history
of hypertension or glaucoma.
The subjects were seated
and
resting blood pres-
sure
, pulse
rate,
central
retinal
arterial
pressure,
and
intraocular
pressure were measured. The sub-
jects
were
then
inverted
for a
3-minute-period.
During
the
inversion period, systemic blood pres-
sure
was
measured
at
45 seconds
and
at
3 minutes;
pulse
rate
was
measured
at
1 minute;
and
central
retinal
arterial
pressure
and
intraocular pressure
were
both
measured
at
3
minutes.
The
subjects
853
/111

were
then
returned
to
the
seated position. All four
parameters
were
remeasured
within
1
minute
after
the
subject was
returned
to
the
upright
pos-
ture,
with
the
subject seated.
Pulse
rates
were
taken
from
the
radial
pulse of
the
right
wrist
. A
Propper
sphygmomanometer
and
a
Litmann
cardiology
stethoscope
were
em-
ployed
to
measure
blood
pressure
with
the
right
arm
supported
laterally
at
the
heart
level
for
all
measurements
(Fig. 1).
Intraocular
pressure
was
measured
utilizing a MacKay-Marg
Model12
ap-
planation tonometer (Fig.
2).
Ophthalmodynamom-
etry
was used to
measure
central
retinal
arterial
pressure.
7
In
this
technique,
the
instrument
probe
of
the
tonometer
was
placed
on
the
sclera
of
the
anesthetized
eye (1-2 drops 0.5
percent
propara-
caine
HCl)
just
adjacent
to
the
limbus
.
The
arte-
ries were visualized
using
a direct ophthalmoscope
at
the
optic
disc.
At
first
pulsation
of
the
arte-
ries
,
the
pressure
was
recorded.
The
pressure
on
the
globe was
then
continually increased
until
pul-
sation
ceased. The first
pulsation
was recorded
as
the
diastolic
pressure;
the
latter
as
the
systolic
pressure.
854/112
Fig.
1.
Blood pressure values
of
subjects were recorded
at
45 seconds
and
3 minutes while in the inverted position.
Fig. 2.
Intraocular
and
central retinal artery pressures were recorded with the MacKay-Marg
applanation tonometer
at
3 minutes while in the inverted position.
Means
and
standard
errors were calculated for
the
following parameters: systemic systolic blood
pressure, systemic diastolic blood pressure, pulse
rate,
central
retinal
systolic
arterial
pressure, cen-
tral
retin
'
al
diastolic
arterial
pressure,
and
intra-
ocular pressure.
The
primary
method of
statistical
analysis
was
an
overall
analysis
of
variance
for
each of these
parameters
.
To
determine
the
signifi-
cant
sources of variation, analysis of variance was
used
again
to
make
multiple comparisons between
adjacent
time
intervals.
8
Results
Systemic blood pressure
and
pulse rate
Both systolic
and
diastolic pressures increased on
inversion,
remained
relatively constant
during
in-
version,
and
returned
to
normal
on
resuming
an
upright
posture. Table 1
and
Figure
3 show blood
pressure
levels before,
during,
and
following in-
version.
Analysis
of
variance
indicates
that
the
rise observed when subjects were inverted
and
the
drop observed when normal posture was resumed
were
highly
significant
(p<.001).
During
the
in-
version period
the
blood pressures fell slightly,
but
July
1983/
Journal
of AONvol. 82/no.
11

only
the
change
in
systolic
pressure
was
signifi-
cant
(p
<.05).
Pulse
rate
prior
to
inversion
was
67
±
1.44.
After 1
minute
of inversion,
the
average
rate
was
78
±
1.09
(p
<.001). One
minute
after
resuming
an
upright
posture,
the
pulse
rate
was
still
signifi-
cantly
elevated
(75
±
1.71) above
pre-inversion
levels.
Central retinal arterial pressure
and
intraocular pressure
Systolic
central
retinal
pressure, diastolic
central
retinal
pressure,
and
intraocular
pressure
all
in-
creased
(p
<.001) on inversion
and
returned
to nor-
mal
on
resuming
an
upright
posture
. Table 2
and
Figures
4
and
5 show
these
pressures
before, dur-
ing,
and
following
inversion.
The
central
retinal
systolic
and
diastolic blood
pressures
and
the
in-
traocular
pressure were
all
significantly elevated
during
inversion. No significant differences were
found
between
pre-inversion
and
post-inversion
values.
Central
retinal
arterial
pressures
had
a
tendency to
remain
slightly elevated
in
the
post-
inversion period,
but
this
was
not
statistically
sig-
nificant.
Discussion
The
results
of
our
study
indicated
a
rise
in
blood
pressure,
pulse
rates,
retinal
arterial
pressures,
and
intraocular
pressures
despite
the
subject's
lack of physical activity while
in
the
inverted posi-
tion.
The effects of
gravity
on
the
physiology of hemo-
dynamics
are
such
that
distensible
blood vessels
experience
variable
responses
in
pressure
and
flow.
For
example,
if
a 5-foot 7-inch
tall
subject
in
the
standing
position
had
a
mean
arterial
blood
pressure
(MAP)
at
the
level of
the
heart
of
100 mm.
Hg,
then
the
MAP
at
the
level of
the
feet (130 em.
below
the
level of
the
heart)
would be (100 + 95)
=
195
mm
.
Hg
(each em.
of
blood
exerts
a
pressure
equivalent
to .735 mm. Hg). Conversely,
the
MAP
in
the
cerebral
artery
(located
approximately
46
em. above
the
level of
the
heart)
would be (100 -
34)
=
66
mm.
Hg.
Because
of
this
effect,
it
has
been
estimated
that
when
an
individual
shifts
from
the
supine to
the
standing
position, approxi-
mately
500 ml.
ofbl~od
are
pooled
in
the
legs. This
can
result
in
a decreased cardiac
output
of 2 liters/
minute
and
a 40
percent
reduction
in
stroke
vol-
ume.9
It
is reasonable to speculate
that
in
the
inverted
position
the
right
atria
of
the
heart
would receive
at
least
an
extra
500 ml. of venous blood which, ac-
cording to
Starling's
Law, would increase cardiac
output
and
also
raise
systemic
blood
pressure.
It
should be noted, however,
that
emotional
and
psy-
chologic factors could
have
contributed to
the
ob-
served
increases
in
systemic
blood
pressure.
In
fact,
the
increase
in
pulse
rate
suggests a
neural
component to
the
rise
in
blood pressure.
In
a
study
of six
human
subjects placed
in
a
-20°
head
down
position for 3 hours,
Katkov
and
associates
10
found
changes
in
ventricular
systolic
pressure
consistent
with
increased
headward
blood shifts. These find-
ings include elevated
right
ventricular
pressures
and
decreased
left
ventricular
pressures.
In
his
study,
Katkov
found
increased
pulse
rate
and
gradually
decreasing systolic
and
diastolic blood
pressure values.
10
This
last
finding
was
inconsis-
160
120
iii
80
.,
~
J::
E
.s
~
~
£
40
8
iii
Pre-
inv
ers
io
n
BLOOD
PRESSURE
MEASUREMENTS
DURING
INVE
RSION
1
0
DIASTOLIC
Inve
rsion
Per
iod
M
easured
m Minutes
1
4
Pos
t-
inwrsion
*
Siqnificonfly di
ff
er
ent
(p<
.OOI) fr
om
both
pre
-inver
sion
an
d
pos
t
-inve
r
sion
.
No d
iff
erences were found between pre- and post
-i
nversi
oo
values.
Fig
. 3.
Graph depicting blood pressure variation with change in
posture.
TABLE
1.
SYSTOLIC AND DIASTOLIC SYSTEMIC BLOOD PRESSURE BEFORE, DURING, AND FOLLOWING INVERSION. VALUES SHOWN ARE MEAN
AND STANDARD ERROR FOR 20
SUBJE
CTS.
Pre-inversion
Inversion
Inverted
Post-inversion
seated
45 sec.
3min.
seated
Systolic blood
pressures
(
mm.
Hg
)
119
±
2.63 157
±
4.22* 148
±
3.70* 123
±
2.64
Diastolic blood
pressures
(
mm.
Hg
)
74
±
1.81 93
±
1.93* 90
±
2.11* 75
±
1.99
*Significantly different (p<
.OOl
)
from both
pre-inversion and
pos
t-inversion.
No
differences
wer
e
found
between
pre-
and post-inversion values.
Effects of gravity inversion procedures 855/113

160
120
~.
"'
r
E
eo
5
~
~
~
"0
0
0
iii
40
P\'e-inversion Inve rsion
Period
Measures in Mi nutes
4
Fbst
-
inversion
• Significantly hi<jler than
prei
n
~on
le...els
{p<.OOI).
No
signi
ficant
chaocJes
we
re f
ou
nd
be
t
wee
n
pre-
and
post
-i
nversion.
35
30
"'
25
en
"'
:r
E
_§
.
,
.t
20
0
Pl'e
-inve
rs
ion
I
NTRAOCULAR
2
In
version Per
io
d
Measured in Minutes
4
Post-
inversion
• Significantly higher than preinversion levels
(p<
.
OOI)
. No significant changes
were
found
between
pre-
and
post-
inve
r
sio
n.
Fig. 4.
Graph depicting the central retinal artery pressure variation with change in p
os
ture.
Fig. 5.
Graph dep
ic
ting elevation
in
intra-
ocular pressure with positional chang
es.
TABLE
2.
CENTRAL RETINAL SYSTOLIC AND DIASTOLIC PRESSURE AND INTRAOCULAR PRE SSURES
BEF
ORE, DURING AND FOLLOWING INVER-
SION. VAL
UE
S
SH
OWN ARE MEAN AND STANDARD ERROR
FO
R 20 SU
BJE
CTS.
Pr
e-inv
er
sion
Inverted
Post-inversion
s
eat
ed 3
min
.
seated
Systolic
central
retinal
pressure
(
mm
.
H
g)
45 ± 7.
21
105 ± 8.50* 51 ± 8.37
Diastolic
central
retinal
pressure
(
mm
.
Hg
) 26 ± 4.53 62 ± 7.1
8*
32 ± 5.46
Intraocular
pressure
(
mm
.
Hg
) 19 ± 0.57 35 ±
1.
26*
19"
± 0.95
*Significantly higher than pre-inversion le
vel
s (p<.
OOl
).
No
signi
fi
cant changes
we
re
fo
und
between pre-and
post-i
n
ve
r
sio
n.
tent
with
our
study,
and
although
Katkov
's
sub-
jects
were
only
-20
°
inverted
, we feel
that
add
i-
tional
studies
w1th longer inversion
times
would
be useful
in
resolving
whether
adaptation
occurs
at
-90
°
inversion.
Thornburg
and
Lapidies,
11
in
their
study
of ure-
teral
peristalsis
in
eleve~
men
placed
in
a
totally
inverted
position (
-90
°)
for 25-35
minutes
, report-
ed
elevated
systolic
and
diastolic pressures
in
all
subjects.
Pulse
values
in
this
study were found to
be
elevated
in
five
of
their
subjects,
and
decreased
in
the
other
six.
We
speculate
that
cerebral
artery
pressures
,
which
normally
are
lower
than
mean
arterial
pres-
sure
, would be
elevated
above MAP
in
the
inverted
position,
and
this
increase, coupled
with
the
aver-
age
increase
in
systolic (30 mm.
Hg
)
and
diastolic
(20
mm
.
Hg
)
pressures
seen
in
thi
s
study
, could
raise
cerebral
artery
pressures
to
unexpectedly
high
levels.
Thus
,
it
seems possible
that
hyperten-
sive
patients
might
experience a potentially
dan
-
856
/114
gerous
hypertensive
episode while inverted.
The observed increases
in
central
retinal
arteri
-
al
pressure
on inversion
are
likely
related
to
an
in-
crease
in
blood volume
in
the
head
and
neck
and
to
the
correlated
decrease
in
venous
return
from
those
regions.
The
increases
in
intraocular
pres-
sure
presumably
occurred
as
a
result
of
an
in-
creased resistance
to
aqueous outflow from
an
ele-
vation of episcleral venous pressure
similar
to
that
which occurs
when
a person changes from
the
sit-
ting
to
the
supine position.
12 •
13
It
is commonly accepted
that
in
some
patients
an
increase
in
intraocular
pressure
can occur
in
the
absence of
other
changes which
are
seen
in
severe
glaucoma, such
as
visual field loss
and
optic nerve
atrophy. These
patients
may
be considered to
have
intraocular
hypertension.
In
our
experiments
the
large elevation
in
intraocular
pressure which
oc-
curred
with
inversion
could be considered to be
equivalent
to
intraocular
hypertension
and
may
put
some
patients
with
impaired aqueous outflow
July 1983/J ournal of
AOA/vol. 82/no.
11

at
a
greater
risk
of developing
visual
field loss
and
optic
nerve
atrophy
.
It
should be
noted
that
our
subjects
were
invert-
ed for only 3
minutes,
but
many
individuals
par-
ticipating
in
this
"fad"
hang
for 10-20
minute
per-
iods,
with
some exercising
and
lifting
weights
in
the
inverted
position.
Conclusion
Because of
the
significant
elevations
in
systemic
and
central
retinal
arterial
blood
pressures
, pulse
rate
,
and
intraocular
pressure
reported
in
these
experiments,
it
is
our
recommendation
that
cau-
tion
should be observed
in
the
prescription
of
the
use of inversion boots. Clearly,
there
is cause for
concern
in
those
individuals
with
a
history
of
hy
-
pertension,
cardiovascular
disease,
and
stroke.
We feel
that
further
stl.).dy
is
necessary
to evalu-
ate
the
risk
of
patients
with
spinal
fusions of
un-
certain
stability,
weak
spinal
ligaments/
4
reflux
esophagitis, or
patients
on
aspirin
or
platelet
in-
hibitors. A
general
caution
must
be
urged
for
the
elderly who
are
already
a
high
risk
population for
cerebrovascular accident.
Finally
,
it
would be
pru-
dent
to
have
intraocular
pressures
and
visual
fields
checked
before
embarking
on
an
inversion
program.
Appreciation is expressed
to
Thomas W. Allen, D.O.,
FA
-
COl, Richard Bell,
Ph
.D., Carol Claycomb, D.O
.,
Arthur
W.
Hafner,
Ph
.
D.
,
Alison
K.
Hubbard, M.A., Robert E.
Kappler
, D.O
.,
FAAO,
Albert
F . Kelso,
Ph.D.,
Amor
Lowsitisukdi
, Marc Mayer, D.O. , Daniel Richardson,
Ph
.D.,
and
Kenneth
A.
Suarez, Ph.D., Chicago College
of
Osteopathic Medicine, for their assistance.
Effects
of
gravity
inversion procedures
1.
Martin
, R.M.:
The
gravity
guiding
system.
Gravity
Guidance
Inc.,
Pasadena
, Calif., 1982
2. Klein, F. C.: On sports. Wall
Street
J
ourna
l,
p.
28,
21
Oct 82
3. Ade lson, S.: Robert
Martin's
boots were made for
hanging-and
for
overturning
back pain. People 18:125-6, Oct 82
4.
Hang
ten. Flipping over
gravity
boots. Time,
p.
61 , 2 May 83
5.
Plocher, D.W.:
Inv
ersion petechiae. N Eng! J Med 307:1406-7,25 Nov
82
6. Back speciali
sts
hit
"inversion" fad. Medical World News, pp. 49-50,
28
Mar83
7.
Chusid, J .
G.:
Correl
ativ
e
neuroanatomy
and
functional neurology.
Ed. 15.
Lange
Medical Publications, Los Altos, Calif., 1973
8. Keppel, G.: Design
and
analysis. A
researcher
's h
an
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Hall, Inc. , Englewood Cliffs,
N.J
.,
1973
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., St. Louis, 1981
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Accepted for publication
in
May 1983.
Dr.
Klatz
is
an
instructor
in
the
Department
of
Osteopathic
Medicine
at
Chicago College of Osteopathic Medicine, Chicago.
Mr
.
Goldman
is
a fellow
in
the
Department
of
Osteopathic
Medicine
at
CCOM.
Dr
.
Pinchuk
is a
staff
member
in
the
De-
partm
e
nt
of Ophthalmology
at
CCOM. Dr. Nelson is
an
assis-
tant
professor
in
the
Department
of
Osteopathic
Medicine
at
CCOM.
Dr
.
Tarr
is a professor
in
the
Department
of
Physiology
atCCOM.
Dr
.
Klatz
,
Chicago
College
of
Osteopathic
Medicine
,
5200
South
Ellis Avenue, Chicago, Illinois 60615.
857/115