Kinesiology

Lesson 10 of 16

Muscles of respiration

Quiet breathing is driven primarily by the diaphragm and intercostal muscles, with the rib cage and lungs moving in coordination. Accessory muscles can contribute when ventilatory demand increases. Breathing patterns vary with activity, emotion, health, and position. Massage should support comfort and never interfere with breathing or prescribed respiratory care.

Key points

• During inspiration, diaphragm contraction increases thoracic volume as its domes descend.
• External intercostals assist rib elevation; internal intercostals have region- and task-dependent roles, especially in forced expiration.
• Quiet expiration is largely passive due to elastic recoil.
• Abdominal muscles can contribute to forced expiration by increasing abdominal pressure.
• Scalenes and sternocleidomastoid may assist inspiration when demand rises.
• Observe breath comfort and pause if a position causes breathlessness or distress.

Key terms

Diaphragm

O: xiphoid, lower ribs, and lumbar crura; I: central tendon; A: contracts to enlarge thorax for inspiration.

External intercostals

O: inferior border of rib above; I: superior border of rib below; A: elevate ribs during inspiration.

Internal intercostals

O: costal groove of rib above; I: superior border of rib below; A: interosseous fibers assist forced expiration, interchondral fibers can elevate ribs.

Serratus posterior superior

O: lower cervical/upper thoracic spinous processes; I: ribs 2-5; A: assists rib elevation.

Serratus posterior inferior

O: lower thoracic/upper lumbar spinous processes; I: ribs 9-12; A: assists lower-rib stabilization and respiratory movement.