Breathing is the result of three-dimensional shape changes in both the thoracic and abdominal cavities. The thoracic cavity is a flexible air container capable of changing volume. By alternately increasing and reducing volume within, pressure differentials are created and air is driven in and out of the lungs. This cavity functions much like a bellows, with air rushing in when expanded and rushing out when squeezed or compressed.
Directly below the thoracic cavity is the abdominal cavity. Unlike the thoracic cavity, the abdominal cavity is a flexible fluid container and cannot change volume. The contents of this cavity are redistributed as the thoracic cavity changes volume, much like a water balloon changes shape when you push on any side of it.
The thoracic and abdominal cavities are separated by the dome-shaped diaphragm muscle. This muscle forms a horizontal seal around the bottom of the rib cage, beginning at the xiphoid process of the sternum and wrapping around to the lumbar vertebrae. Imagine opening an umbrella inside the rib cage from the bottom up. The handle of the umbrella is much like the central tendon, which pulls the fabric of the umbrella down, flattening it during muscle contraction, increasing thoracic cavity volume, and driving inhalation. The abdominal cavity must shift, expanding side to side and front to back as the dome flattens and the thoracic cavity expands.
Proper function of the breathing mechanism depends on the mobility of all sides of the rib cage and the abdominal cavity, as well as coordinated activation of the diaphragm and associated breathing muscles. Rigidity or obstruction of movement in the expansion or recoil movement of the thoracic cavity, or that of the abdominal cavity, can impede normal breath. Additionally, postural deviations that limit thoracic or abdominal mobility in any direction may also be restrictive. Ensuring mobility of both cavities in all directions maximizes breathing efficiency and reduces stress on the diaphragm and the associated respiration muscles.

Facilitating Breath
Positioning: client supine.
1. Standing at the client’s side, place both hands on the client’s anterior chest (A).
2. Instruct the client to breathe deeply into the chest as you gently and firmly press posteriorly and inferiorly. Repeat several times.
3. Place one hand on each side of the lower rib cage (B).
4. Instruct the client to breathe deeply into the abdomen and sides as you gently and firmly squeeze the rib cage medially.

Client Homework—Cat/Cow Pose
1. Start on your hands and knees with your palms flat. Align your wrists and elbows directly under your shoulders and your knees under your hips.
2. To perform the cat pose, exhale and round your spine toward the ceiling as you relax your head, allowing your chin to drop toward your chest.
3. Focus on spreading your ribs apart as you round your back.
4. Reverse to cow pose as you inhale, allowing your back to sag
while you lift your head and open your ribs and chest.
5. Repeat the sequence, alternating between cat and cow with
your breath.

Respiration
Respiration Muscles
• Inhalation: Diaphragm, external intercostals, serratus posterior superior and inferior, scalenes, pectoralis major and minor, quadratus lumborum, serratus anterior
• Forced exhalation: Internal intercostals, transverse abdominis, internal and external obliques, rectus abdominis
Actions
• Inhalation: Rib cage expansion decreases air pressure within the thoracic cavity, air moves into the lungs
• Exhalation: Rib cage compression increases air pressure within the thoracic cavity, air moves out of the lungs

Christy Cael is a licensed massage therapist, certified strength and conditioning specialist, and instructor at the Bodymechanics School of Myotherapy & Massage in Olympia, Washington. Her private practice focuses on injury treatment, biomechanical analysis, craniosacral therapy, and massage for clients with neurological issues. She is the author of Functional Anatomy: Musculoskeletal Anatomy, Kinesiology, and Palpation for Manual Therapists (Lippincott Williams & Wilkins, 2009). Contact her at functionalbook@hotmail.com.