The respiratory muscles during exercise

From a functional point of view, there are three groups of respiratory muscles: the diaphragm, the rib cage muscles and the abdominal muscles. Each group acts on the chest wall and its compartments, i.e. the lung-apposed rib cage, the diaphragm-­apposed rib cage and the abdomen. Contraction of the diaphragm expands the abdomen and the lower part of the rib cage (abdominal rib cage). The rib cage muscles, including the intercostals, the parasternals, the scalene and the neck muscles, mostly act on the upper part of the rib cage (pulmonary rib cage) and are both inspiratory and expiratory. The abdominal muscles act on the abdomen and the abdominal rib cage and are expiratory. When each muscle group contracts alone or the contraction is predominant compared to the other groups, undesirable effects (such as “paradoxical” inward or outward motion during inspiration and expiration, respectively) occur on at least one of the compartments. A highly coordinated recruitment of two or three muscle groups is required to avoid these effects. During breathing at rest, this is accomplished by the coordinated activity of the diaphragm and inspiratory rib cage muscles. Normally no expiratory muscles are used [1].
Although during exercise respiratory muscles are finely controlled, they can contribute to limit performance http://ow.ly/qYUc300m9uP