The Science

In traditional anatomy, respiratory muscles are categorized as primary and accessory muscles. However, most anatomical studies focus on quiet breathing—the passive, at-rest function of the respiratory system—while research on active breathing—breathing that occurs during physical activity, exercise, or breathwork practices—is limited.

Primary and Accessory Respiratory Muscles

  • Primary muscles include the diaphragm and external intercostals, which manage quiet breathing.

  • Accessory muscles, such as various chest and neck muscles, assist by lifting the rib cage.

Under normal conditions, primary respiratory muscles are sufficient for quiet breathing with minimal involvement from accessory muscles. However, when someone predominantly relies on accessory muscles for breathing, it may indicate a dysfunctional breathing pattern, which can be caused by stress, poor posture, or health conditions.

Active Breathing and Core Muscle Interaction

During active breathing (e.g., movement, exercise, or deep breathing techniques), accessory muscles support and enhance the function of the primary muscles, rather than replace them. The diaphragm, the most essential breathing muscle, works in complementary opposition with the transverse abdominis, similar to how the biceps and triceps work together to control arm movement. This interdependent relationship between the breathing and core muscles is key to efficient, powerful movement and overall respiratory health.

Supporting Muscles

Several muscles also support the primary and accessory respiratory muscles, enhancing their function during breathing:

  • Chest and upper limb muscles help lift the rib cage, expanding the diaphragm’s range of motion and creating more space for lung expansion.

  • The transverse abdominis, which controls abdominal contraction, is supported by the oblique abdominal muscles and lower limb muscles like the glutes, quadriceps, and gastrocnemius.

  • Internal Intercostal muscles contract to compress the rib cage during exhalation, helping efficiently expel air from the lungs.

Coordination of Respiratory and Core Muscles

The primary, accessory, and supporting muscles of inhalation and exhalation work in coordinated, rhythmic sequence, controlled by the respiratory control center in the brain. This center processes input from the carotid artery, muscles, lungs, and emotional and cognitive centers of the brain, ensuring that breathing remains optimized for any situation—whether at rest or in motion.

Inhalation Process

During inhalation, the inspiratory muscles engage and expand the rib cage, filling the lungs with air. As the lungs reach capacity, these muscles release, and the lung tissue and surrounding muscles return to their natural position.

Exhalation Process

During active breathing, exhalation becomes more forceful. Exhalation muscles contract to narrow the torso and compress the lungs, expelling more air. When the exhalation muscles are released, the body and lungs return to a neutral state, ready for the next breath cycle. This continuous interplay between activation and release ensures efficient, controlled breathing, seamlessly integrating respiration with movement and overall physiological function.