Diaphragm and parasternal muscle recruitment, thoracoabdominal motion, and dyspnea responses to upper extremity exercise with normal breathing and inspiratory resistance breathing

Reduced upper extremity endurance is a response to dyspnea in chronic obstructive pulmonary disease (COPD). Physiological mechanisms contributing to this response include the competitive roles of the respiratory muscles during unsupported upper extremity exercise (UUEE) in COPD. The respiratory muscles are recruited to assist respiration and stabilize the chest wall during UUEE. The purpose of this quasi-experimental laboratory investigation was to describe and compare physiological responses of the respiratory muscles to arm exercise under two conditions: normal and inspiratory resistance breathing. The specific aims of the study were to: (1) determine the effect of UUEE on diaphragm and parasternal muscle electromyogram (EMG) signal amplitudes, the pattern of thoracoabdominal motion measured with Respitrace plethysmography, and the intensity of dyspnea measured with the visual analog scale; (2) identify relationships between EMG amplitudes, thoracoabdominal motion, and dyspnea; and, (3) compare respiratory muscle EMG amplitudes, the pattern of thoracoabdominal motion, and dyspnea between normal and resistance breathing. The sample consisted of 18 normal adult subjects between the ages of 33 and 47. Data were collected during arm rest and UUEE. Subjects served as their own controls.;Pertinent study findings are: (a) UUEE resulted in significant increases in inspiratory diaphragm EMG amplitudes, and inspiratory and expiratory parasternal muscle EMG amplitudes during normal breathing; (b) arm exercise was also associated with prolonged and dysphasic parasternal muscle contractions; (c) expiratory contraction of the inspiratory muscles occurred with asynchronous breathing patterns and in association with an increase of the sensation of dyspnea; (d) breathing against resistance resulted in significant increases in diaphragm, rib cage and accessory muscle recruitment, and significant increases in the sensation of dyspnea; and, (e) significant negative correlations were observed between the sensation of dyspnea and inspiratory diaphragm and parasternal muscle recruitment, such that dyspnea increased as recruitment of the diaphragm and parasternal muscle fibers decreased. These findings add to the knowledge of: (a) respiratory muscle recruitment during rest and arm exercise with normal breathing and inspiratory resistance breathing; and (b) the relationship between respiratory muscle recruitment and dyspnea. The findings also suggest clinical roles for: (a) dyspnea ratings in evaluation of patients with COPD, and (b) diaphragmatic breathing in the management of dyspnea in COPD.