Neuromuscular control of airflow through the oral and nasal passages during exercise

The respiratory upper airway musculature controls airway resistance by regulating the dimensions and compliance of the pharyngeal and nasal passages. Little is known about the neural control of the upper airway dilator muscles during exercise. The purpose of this investigation was to determine the correlation between airflow through the nose and mouth with the activity of the nasal dilator and genioglossus muscles, respectively. Correlations were determined between peak inspiratory nasal flow (V̇_N) and peak integrated nasal dilator muscle EMG activity (iEMG_NDM) as well as between peak inspiratory mouth flow (V̇_M) and peak integrated genioglossus EMG activity (iEMG_GG) during exercise. Healthy subjects (5male/2female;31.9±8.9yrs) performed incremental cycle ergometry to volitional fatigue. V̇_N and V̇_M (L/sec) were measured with separate pneumotachs attached to a custom face mask. EMG_NDM activity was recorded with surface electrodes over the nares. EMG_GG activity was recorded with a single fine wire electrode in the belly of the muscle. We found significant correlations between V̇_N and iEMG_NDM (p<0.001; r=.66) and between V̇_M and iEMG_GG(p<0.001; r = .59) during exercise. Results suggest that increases in nasal and mouth flow are associated with increased EMG activity of the nasal dilator and genioglossus muscles, respectively. Activation of pharyngeal and nasal dilator muscles during exercise may contribute to the regulation of upper airway resistance, enabling ventilation to increase while minimizing increases in the work of breathing.