Tanaka T, et al. - A systematic review was performed to synthesize estimations of inspiratory muscle oxyhaemoglobin (O₂Hb), deoxyhaemoglobin (HHb), blood volume and flow of the inspiratory muscles acquired via near-infrared spectroscopy (NIRS) amid cycling, hyperpnoea and loaded breathing in healthy non-athletes, healthy athletes and patients with chronic obstructive pulmonary disease (COPD) or chronic heart failure (CHF). Amid different regimens of hyperpnoea or loaded breathing, comparisons of inspiratory muscles exhibited that the sternocleidomastoid deoxygenated more than the intercostals, parasternals or scalenes. Assessing inspiratory muscle deoxygenation via NIRS can inform mechanisms of inspiratory muscle limitation in non-athletes, athletes and patients with CHF or COPD.