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Sequence of action of the diaphragm and quadratus lumborium during quiet breathing.

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Sequence of Action of the Diaphragm a n d Quadratus
Lumborium duri:ng Quiet Breathing ’
Y e w Y o r k Medical College, Department of A n a t o m y , N e w Y o r k City, N . Y .
A smies of 15 rabbits had multiple intercostal clip electrodes implanted in the diaphragm and quadratus lumborum at open operation.
Leads from the electrodes were passed to the back of the animals and soldered
to a junction band. Simultaneous recordings of electromyographic activity and spirometry were made following recovery.
The study revealed that the quadratus lumborum, acting simultaneously with the
diaphragm, is an effective inspiratory muscle stabilizing the twelfth rib, converting i t
into a fixed point from which the diaphragm acts. Very possibly the action of the
quadratus pulls down the lower rib helping to increase the costo-diaphragmatic recess.
Like the sternal, crural and costal portions of the diaphragm, the quadratus exerts a
braking action to oypose the normal elastic recoil of the lungs during expiration.
While investigating the activity of the
diaphragm during normal quiet breathing,
it became of interest to earn the sequence
of action of this muscle and the quadratus
lumborum, for the literature makes no reference to any electromyographic studies of
this nature, or for that matter, to any
studies of the behavior of the quadratus
Since there is a relatively small attachment of the quadratus to the thorax, it
has been felt that it is unlikely to be of
much importance in .he mechanics of
breathing. The general opinion is that the
quadratus lumborum acts as an inspiratory muscle which helps to fix the lower
ribs and thus to convert them into fixed
points from which the diaphragm can
In order to clarify these points, it was
thought worth while 1 0 study the subject with precise electromyographic techniques.
Experimental animals. Fifteen adult
male rabbits, weighing 8-10 lbs, were the
Equipment. The equipment centered
on a Hathaway Type SC-16A recording
C.R. oscillograph consisting of six identical but separate amplifers each of which
is fitted with a 3” cathode-ray tube. The
traces of the tubes were photographed by
means of built-in chart drive system deANAT. REC., 151: 579-582.
signed for recording transient or periodic
Although there is a constant sweep of
the traces on the tubes, the beams of the
recording tubes have no x-axis deflection;
this is provided by the continuous movement of the film through the chart drive
Independent Disa amplifiers, identical
in construction, were used as pre-amplifiers. Each is a balanced four-stage a-c
amplifier with an input circuit designed
especially to accomplish a low noise level,
a high input impedance, a wide frequency
range, and a large inphase rejection ratio.
Electrodes. A dual clip electrode of
new design used to study intercostal activity was utilized in this investigation
(fig. 1).
It consists of two no. 0 “Petite” paper
fasteners insulated with “Formvar” except
for the tip of each jaw, soldered to the
ends of no. 40 dual insulated stranded
Surgical procedure for implanting electrodes. Each rabbit was anaesthetized
with pentobarbital (Nembutal 0 . 3 ml/lb
body wt), and maintained with ether when
With the animal supine on an adjustable operating table, a long horizontal
incision through all muscle layers was
made below the costal margin.
‘This study was supported by an N.1.H grant,
NB 04771-01 to Dr. Boyd.
Fig. 1
Dual intercostal clip electrodes.
x 20.
The diaphragm was exposed by depressing the liver, and the quadratus lumborum was exposed by gently pushing
aside the colon and the kidney.
Electrodes 2 mm apart were clipped to
the crus, sternal and costal slips of the
diaphragm, and to the quadratus lumborum. With the aid of a large curved
autopsy needle, the insulated stranded
wires leading from the electrodes were
drawn between the muscles of the lateral
abdominal wall and the skin, around to
the back of the animal. The free ends of
the wire were brought out through puncture holes in the skin and soldered to a
“junction band” which was then taped
securely to the animal’s back. The incision
was closed, sprayed with an antibiotic
plastic dressing, and covered with sterile
gauze held in place by elastic adhesive
After several days of recovery, the animals underwent a series of tests which
involved a simultaneous recording of electromyographic activity and spirometry.
The small modified spirometer used for
recording respiratory movements is discussed elsewhere (Boyd and Basmajian
The experimental animals were tested
on 3 or 4 occasions, and the data for study
was obtained from these recordings. The
EMG activity was rated from 0 to 3+.
One plus ( 1 + ) indicates slight activity,
two plus ( 2 + ) moderate activity, and
three plus ( 3 + ) great activity.
The quadratus lumborum. Since the
diaphragm in the rabbit has been considered elsewhere (Boyd and Basmajian,
’ 6 3 ) , it is necessary only to describe the
quadratus lumborum.
The quadratus lumborum, broader below than above, takes origin from the
ilio-lumbar ligament and from the iliac
crest. As it passes upwards, it gives several fibers to the transverse processes of
the lumbar vertebrae, and eventually
reaches its insertion on the medial three
Fig. 2 Typical recording of activity during quiet breathing from the quadratus lumborum ( B ) , and from the crus of the diaphragm ( A ) . The numbers below the spirometric
tracing refer to the phases in the respiratory cycle. Pre-inspiration (phase l), inspiration
(phase 2), terminal phase of inspiration (phase 3), pre-expiration (phase 4 ) , expiration
(phase 5 ) .
fourths of the last rib by passing behind
the diaphragm. Its ~ppennost part is
therefore covered with pleura.
The respiratory cycle. The spirometric
tracings show the same phasic tendency
seen in other studies o n respiratory muscles, and are described elsewhere (Boyd
and Basmajian, '63).
T h e recordings. Surveys of the recordings (fig. 2), revealed that both the diaphragm and the quadratus lumborum
were slightly active 1(1+) during preinspiration (phase l ) , but activity in both
muscles showed signs of change at the
onset of inspiration (phase 2).
In the diaphragm, s:ight activity ( l + )
was recorded for the first 60-70msec of
inspiratory phase 2, fctllowed by a sharp
increase to moderate 2 ctivity for another
60-70 msec of the phxse. Great activity
( 3 f ) followed for the next 70-80 msec,
which quickly returned to moderate activity (2+) for the last 10-20msec of inspiratory phase 2.
The slight activity recorded during the
10-15msec of inspiratory phase 3, abruptly terminated at the onset of preexpiration. In most instances, just noticeable to slight activivi ( 1 + ) continued
throughout pre-expirat ion and expiration.
In the typical recordings presented in
figure 2, the clip was on the crus, which
was electrically silent throughout preexpiration and expiration. In all other
parts of the diaphragm, slight activity
( 1+ ) was always re1:orded during preexpiration and expiration.
In contrast to diaphragmatic activity,
the quadratus showed only slight activity
during the first 110-120 msec of inspiration. This, in fact, was throughout nearly
the entire first half of inspiratory phase 2.
Moderate activity (:I+) recorded at the
onset of the second half of phase 2 lasted
60-70 msec but quickly increased to great
activity ( 3 + ) for the next 70-80 msec,
returning to moderat68 activity (2+) for
the last 10-15msec of this phase.
Although the diaphragm showed slight
activity during inspiratory phase 3, the
quadratus was electrically silent through-
58 1
out this phase and the pre-expiratory
phase as well.
The slight activity ( I f ) recorded from
the quadratus muscle throughout expiration was identical to that recorded from
the sternal and costal parts of the
The recordings reveal that the force of
diaphragmatic contraction increases gradually during the early stages (first half)
of inspiration. It is very likely that this
gradual increase is proportional to the
amount of resistance to stretch in the
tissues of the lungs, mediastinum and
thoraco-abdominal parietes. During the
latter part of inspiration (second half)
the expenditure of energy by the diaphragm is considerably increased, and it is
maintained at a higher level throughout
all but the last few milliseconds of the
phase. The effect of diaphragmatic contraction with no opposing muscle action
would tend to elevate the twelfth rib, thus
causing a less effective lowering of the
dome of the diaphragm and impairing
somewhat the efficiency of inspiration. Any
ascent of the twelfth rib is partially prevented by the action of the quadratus
During the early stage of diaphragmatic
contraction, the quadratus lumborum is
only partially utilized to stabilize the lower
rib, for it is possible that other more passive structures such as fascia and ligaments act as sufficient stabilizers at this
time. However, during the later more
energetic phase of diaphragmatic contraction, the quadratus lumborum rapidly and
progressively becomes more active in resisting stretch in order to bring about a
greater stability of the rib. In addition, it
is possible that the quadratus somewhat
depresses the rib, thus helping to increase
the costo-diaphragmatic recess.
Boyd, W. H., and J. Basmajian 1963 Electromyography of the diaphragm in rabbits. Am.
J. Physiol., 204: 943-948.
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quadrature, sequence, diaphragm, action, quiet, breathing, lumborium
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