Neural drive to nasal dilator muscles: influence of exercise intensity and oronasal flow partitioning.
Level 4 - case-series / case-control
Small laboratory physiological study in healthy humans without a randomized control.
PubMed 8567580 · doi:10.1152/jappl.1995.79.4.1330
What was done
Researchers measured total and nasal inspired ventilation (VI) alongside alae nasi (AN) muscle electromyography (EMG) in 7 subjects during progressive-intensity bicycling exercise up to 90% of maximal power. In a separate experiment in 6 subjects, anterior rhinomanometry was used to measure nasal pressure-flow relationships to determine the nasal VI at the transition from laminar to turbulent airflow.
What was found
Nasal VI accounted for 70 ± 11% of total VI at rest and declined to 27 ± 8% (SE) at 90% maximal power. Nasal VI and integrated AN EMG activity increased linearly up to 60% maximal power before plateauing, even as total VI rose exponentially between 60% and 90% maximal power. This exponential rise in total VI coincided with a sharp increase in oral VI and the onset of marked nasal flow turbulence.
Why it matters
The study suggests neural drive to nasal dilator muscles scales with nasal airflow rather than general central respiratory drive. It also indicates nasal airflow turbulence may be the mechanical trigger prompting the switch to oronasal breathing to minimize total pulmonary resistance during heavy exercise.
Limits
The sample size is very small (n = 7 for exercise, n = 6 for rhinomanometry) and participant demographics are not reported in the abstract. The specific sensory receptors or neural pathways linking airway resistance to alae nasi motor drive were not directly tested or identified.
Cited by
- supports During vigorous or intensive exercise, the majority of ventilation transitions to oral (mouth) breathing.