Respiratory muscle electromyogram and mouth pressure during isometric contraction

• Published in: Respiratory physiology & neurobiology Vol. 137; no. 1; pp. 51 - 60
• Main Authors: Yokoba, Masanori, Abe, Tadashi, Katagiri, Masato, Tomita, Tomoyuki, Easton, Paul A.
• Format: Journal Article
• Language: English
• Published: Amsterdarm Elsevier B.V 14-08-2003; Elsevier
• Subjects: Adult; Air breathing; Biological and medical sciences; Electromyography; Fundamental and applied biological sciences. Psychology; Humans; Isometric Contraction - physiology; Male; Mammals, humans; Methods, electromyography; Mouth - physiology; Muscle, respiratory, extra-diaphragmatic; Neck Muscles - physiology; Pressure; Respiratory Muscles - physiology; Respiratory system: anatomy, metabolism, gas exchange, ventilatory mechanics, respiratory hemodynamics; Vertebrates: respiratory system; Methods, electromyography; Muscle, respiratory, extra-diaphragmatic; Mammals, humans; Human; extra-diaphragmatic; Electrophysiology; Isometric muscular contraction; Mammals; Respiratory system; Pressure; Oral cavity; electromyography; Muscle; humans; Methods; Respiratory muscle; Electromyography; respiratory
• ISSN: 1569-9048; 1878-1519
• DOI: 10.1016/S1569-9048(03)00092-2

When extra-diaphragmatic muscles are activated progressively under approximately isometric conditions, we expect a corresponding increase in respiratory muscle output. Therefore, we examined relative recruitment shown as the latency to onset of EMG activity, and the relationship between mouth pressure and electromyogram activity of the neck accessory and transversus abdominis (TRANS) muscles during respiratory maneuvers against occlusion. Fine wire electrodes were inserted into the scalene (SCLN), sternocleidomastoid (STERNO), trapezius (TRAPZ) and TRANS in six awake, healthy subjects. Mouth pressure, raw and moving average EMG signals were recorded during gradual production of expiratory or inspiratory mouth pressure to maximum (MP
max) at FRC in the standing posture. Group mean linear regression lines of EMG activity versus mouth pressure were strongly significant for SCLN and TRANS, less for STERNO, and least for TRAPZ. The SCLN and STERNO showed EMG activities with low, and TRAPZ showed EMG activity only with high, mouth pressure. At 90% MP
max, TRAPZ was much less active compared with TRANS, SCLN, or STERNO. These results suggest that over a wide range of respiratory effort there is a significant difference in the relationship between mouth pressure and EMG activity in the accessory muscles, with differential recruitment of individual respiratory muscles.