Besides the metabolic beneficial effects of high-intensity interval training (HIIT), it is able to increase the stress on lung parenchyma. This study examined 6 weeks of HIIT-induced inflammation and airway narrowing of the lung parenchyma in male maturing rats. All animals after 2 weeks of familiarization were divided in 3 groups of base (n = 10), HIIT (n = 10), and control (n = 10).HIITwas performed at speed of 20 m/min and ended at speed of 70 m/min (incrementally increase). Twenty-four hours after, the last training session animal was sacrificed and their lung removed. Lung samples were sectioned in 5 μm, stained with H&E, and studied histologically and histometrically. All these variables were measured at the end of exercise intervention. After 6 weeks of HIIT, measures of intima, media, and adventitia anatomical layers of the bronchi and bronchioles of the respiratory tract were significant than the control group (p = 0.05). Mechanical stress caused by excessive ventilation due to HIIT created histological inflammation in the bronchi and bronchioles of the respiratory tract. Thus, HIIT exercise causes reduction in the diameter of the lung parenchyma ducts that can affect the amount of oxygen consumption and consequently affect athletic performance.
