Expiratory Muscles (primary)

Your Voice: An Inside View by Scott McCoy, DMA

During everyday living, expiration is generally a passive activity. Ordinary people—those who are not trained as pulmonary athletes the way singers are— inhale by gently contracting the diaphragm while simultaneously lifting the entire thorax. This technique is often called clavicular breathing, since it is accompanied by a lifting of the clavicles and shoulders. In this breath, the natural elastic recoil of the lungs and the weight of gravity pressing down upon the thorax are sufficient to generate respiratory force. As physical exertion increases, however, additional means are required to induce and control the expulsion of air from the lungs. This is particularly true in breathing for singing. Six different sets of muscles can be considered primary for exhalation; not all, however, are used by every singer or for every variation in breath- ing technique.

The internal intercostal muscles are found on the inside of the ribcage underneath the external intercostals. Their fibers run obliquely away from the midline of the body, criss- crossing their external neighbors and thereby acting as direct antagonists. You can also use your hand to approximate the orien- tation of the internal intercostals in the body; this time, however, cross your right hand over and place it on the left side of your ribcage with the fingers pointing down toward your hip. Your fingers will now point in the general direction of the internal intercostals.

Each internal intercostal muscle originates from the lower rib and inserts into the rib above it. Upon contraction, the higher rib is pulled down and inward toward the lower rib, depressing the ribcage and decreasing its circumference. This, as we know, induces exhalation.
Compared with the external intercostals, the internal muscles lie in a more anterior orientation within the thorax. If their location is again compared with the face of a clock, they occupy the space between approximately 2:00 to 5:00 in the right hemisphere and 7:00 to 10:00 in the left.

Internal Intercostals are voluntary muscles whose control can be learned through the deliberate squeezing of the thorax. In most singing pedagogies, however, their contraction is delayed as long as possible, only becoming significant at the ends of very long or extremely loud phrases. This is because a strong initial contraction in these muscles will over-pressurize the breath, leading to a pressed, strident sound quality.

For many singers, the more important muscles for expiration are found in the abdomen. Five significant pairs of muscles are located in this region: the external oblique, internal oblique, rectus, and transverse abdominis (or abdominal) muscles, which are found in the anterior abdomen; and the quadratus lumborum, which lies in the posterior. These muscles all contribute to expiration either by depressing the thorax, or by compressing the abdominal viscera and thrusting it upward against the underside of the diaphragm to help deflate the lungs.

The four sets of anterior abdominal muscles form a complex, interlaced structure of great strength and flexibility. At its center lies the paired rectus abdominis.

These long muscles have fibers that run longitudinally (in the rectus orientation as discussed in the previous Chapter), originating from tendons attached to the pubic bones and inserting into the cartilaginous portions of the fifth through seventh ribs and the xiphoid process at the base of the sternum. Each rectus is divided into four sections, called bellies, which can be contracted simultaneously or inde- pendently—the classic example of independent contraction is seen in the middle-eastern “belly dancer.”

When the rectus is contracted, the rib cage is pulled toward the pelvis, arching the back forward. Many people use exercises such as sit-ups, crunches and leg-lifts to strengthen the rectus. Carried to the extreme, these exercises result in the “ripped” abdomen or “six-pack” sometimes associated with body builders. Strenuous exercise of the rectus probably has little positive effect for singers beyond the improvement of physical appearance. Since its action is to shorten the distance from the pubis to the thorax, contraction of the rectus does little to compress the viscera when appropriate singing posture is maintained.
Surrounding the rectus muscles is a tendinous sheath formed by the division of the abdominal aponeurosis, which extends from the sternum to the pubis. The remaining anterior abdominal muscles all attach at some point to the aponeu-rosis at the lateral edges of the paired rectus.

The three remaining pairs of anterior abdominals encircle the lower torso from the spine to the rectus. Beginning with the outermost layer, we find the external oblique abdominis muscles. Like the external intercostals, these muscles have oblique fibers that run downward toward the midline of the body.

They originate in the exterior thorax, attaching to ribs five through twelve, and insert into the iliac crest of the pelvis and the abdominal aponeurosis adjacent to the rectus muscles. Because they cover the largest surface area of any of the abdominal muscles, the external obliques are particularly important expiratory muscles for singers.

Continuing more deeply into the torso, we find the internal oblique abdominis muscles, whose fibers run approximately perpendicular to those of the external obliques. They originate from the iliac crest and the inguinal ligament—a ligament that runs from the pubic bone to the iliac crest, also called the groin ligament—and insert into the aponeurosis and the thorax at ribs nine through twelve.

The deepest layer of abdominal muscle is the transverse, whose fibers run horizontally from the rectus muscles to the spine. Like the internal obliques, the transverse muscles have attachments to the inguinal ligament, the iliac crest and the aponeurosis; at the top, however, they are located in the interior of the thorax where they attach to ribs six through twelve and interlace with portions of the diaphragm.

According to Zemlin, the expiratory functions of the various abdominal muscles are not uniform:

“Because of their attachments and courses, the abdominal muscles probably do not all contribute to expiratory activity to the same degree. On mechanical grounds, the oblique muscles are probably the more effective in depressing the ribs, while the transverse abdominis muscles are more effective in compressing abdominal contents” (Zemlin, 1998).

This is not necessarily bad news for singers. To maintain effective breath support, possibilities must exist for antagonism between the muscles of inspiration and expiration. This can occur between the external intercostals, which elevate the ribs, and the oblique abdominals—both internal and external—which depress the ribs.

The final primary expiratory muscle pair is located in the posterior abdomen, the quadratus lumborum. Named for their rectangular shape (i.e., quadratus) and location in the lumbar region (i.e., lumborum), these muscles originate at the crest of the iliac and insert into the lowermost rib and the transverse processes of the lumbar vertebrae. Two respiratory functions are possible.

Through their attachment to the base of the thorax, they may help stabilize that structure against the downward pull of the diaphragm. More importantly for singers, they act somewhat like a girdle around the lower back, helping to direct the viscera upward toward the diaphragm during contraction of the anterior abdominal muscles. The quadratus lumborum also serve an important postural function, stabilizing the lower back.