Influence of posture and breathing route on neural drive to upper airway dilator muscles during exercise

Abstract

Our purpose was to determine the influence of posture and breathing route on electromyographic (EMG) activities of nasal dilator (NDM) and genioglossus (GG) muscles during exercise. Nasal and oral airflow rates and EMG activities of the NDM and GG were recorded in 10 subjects at rest and during upright and supine incremental cycling exercise to exhaustion. EMG activities immediately before and after the switch from nasal to oronasal breathing were also determined for those subjects who demonstrated a clear switch point (n = 7). NDM and GG EMG activities were significantly correlated with increases in nasal, oral, and total ventilatory rates during exercise, and these relationships were not altered by posture. In both upright and supine exercise, NDM activity rose more sharply as a function of nasal inspired ventilation compared with total or oral inspired ventilation (P< 0.01), but GG activity showed no significant breathing-route dependence. Peak NDM integrated EMG activity decreased (P = 0.008), and peak GG integrated EMG activity increased (P = 0.032) coincident with the switch from nasal to oronasal breathing. In conclusion, 1) neural drive to NDM and GG increases as a function of exercise intensity, but the increase is unaltered by posture; 2) NDM activity is breathing-route dependent in steady-state exercise, but GG activity is not; and 3) drive to both muscles changes significantly at the switch point, but the change in GG activity is more variable and is often transient. This suggests that factors other than the breathing route dominate drive to the GG soon after the initial changes in the configuration of the oronasal airway are made.

Physical Inactivity Is Associated with Moderate-Severe Obstructive Sleep Apnea

“…Exercise activity may positively modulate OSA by increase of upper airway tonus via the recruitment of upper airway muscles for breathing work or head stability. 27,28 Studies examining the effect of physical activity on OSA have not measured muscle tonus, 6,10,11 but instead have examined the mediating effect of obesity. Similarly, methods that have been developed to increase upper airway tonus for the treatment of OSA have not been proven effective.…”

Differential effects of targeted tongue exercise and treadmill running on aging tongue muscle structure and contractile properties

“…Most of the literature concerning the effects of treadmill running on the GG muscle comes from the study of obstructive sleep apnea in respiratory physiology, and they have found that the GG muscle is activated to maintain airway patency and improve airway resistance. During exercise and hypercapnia, increased ventilation was associated with a progressive rise in GG EMG activity during both oral and nasal routes of breathing (21,73,88). Furthermore, activation of the GG muscle, either through hypoglossal stimulation or direct muscle stimulation, dilates the oropharynx to increase inspiratory flow rates and thus improves upper airway flow mechanics, specifically within the pharynx (16,19,23,70).…”

“…Exercise may serve as an effective remediation because recent studies have identified increased GG muscle contraction amplitudes with exercise, as measured with electromyography (EMG) (73,83,88). In addition, exercise-induced increases in GG EMG activity were correlated with increases in nasal, oral, and total ventilatory rates and neural drive to the GG (1,3,20,73,88). However, the optimal type of exercise to employ for improving tongue muscle contractile function and the manner in which different types of exercise may alter GG muscle biochemistry have not been elucidated.…”

“…It may be possible to systematically increase tongue muscle activity not only through targeted tongue exercise, but also with the use of other, nonspecific exercises that serve to increase respiratory drive, such as treadmill running. The rationale for this concept is the previously discussed upregulation of tongue muscle activity and neural drive to the GG that is associated with increased respiratory activity during exercise (1,3,20,73,83,88). Thus, treadmill running may strengthen the tongue musculature and improve overall function by inducing changes in tongue muscle contractile properties and structure.…”

Effect of nasal or oral breathing route on upper airway resistance during sleep

“…However, resistive load perception was not different between the oral and nasal breathing routes [26], suggesting that similar pressure receptors are also present in the pharynx or more distal airways. In addition, although it was initially suggested that the nasal or oral breathing route might have differential effects on pharyngeal dilator muscle activation [27], subsequent work has refuted this finding (although activation of the alae nasae muscle was consistently greater during nasal breathing than oral breathing) [28,29]. Hence, available evidence suggests that pressure receptors in the nose and other parts of the upper airway are responsible for sensing increasing resistance to nasal airflow, and initiating the switch to oronasal or oral breathing.…”