Respiration is fundamental to healthy physiology, psychology and musculoskeletal function. However, few practitioners know about respiratory chemistry and how it regulates our physiology and ability to perform both physically and cognitively. Abnormal respiratory chemistry is common yet its presence is often unrecognized. Over breathing is the most common cause of deregulated chemistry and results in CO2 deficiency or hypocapnia. Hypocapnia can cause a variety of physiological changes which can make recovery very difficult. The presence of hypocapnia can be determined using capnography. Often once the chemistry and mechanics of breathing are re-established, patients with orthopaedic presentations (back pain, neck pain, repetitive strain etc.) that have been resistant to change become more responsive to manual therapy and exercise. Even patients with symptoms normally classified as central sensitization have been shown to improve. This course will discuss the relevance of breathing evaluation in orthopaedic physiotherapy, the supporting evidence and describe case examples.