Contractile properties of human nasal dilator motor units.

The technique of intramuscular microstimulation was used to activate facial nerve fibers while acquiring simultaneous twitch force measurements to measure the contractile properties and force-frequency responses of human nasal dilator (ND) motor units. Twitch force amplitude (TF), contraction time (CT), half-relaxation time (HRT), and the maximal rate of rise of force normalized to the peak force (maximum contraction rate, MCR) were recorded from 98 ND motor units in 37 subjects. The average CT, HRT, MCR, and TF were 47.

Effect of hypoxia on abdominal motor unit activities in spontaneously breathing cats.

These experiments were designed to examine the behavior of external oblique motor units in spontaneously breathing cats during hypoxia and to estimate the contribution of recruitment and rate coding to changes in the integrated external oblique electromyogram (iEMG). Motor unit activities in the external oblique muscle were identified while the cats expired against a positive end-expiratory pressure (PEEP) of 1-2.5 cmH2O.

Measurement of the EMG-force relationship in a human upper airway muscle.

The upper airway muscles play an important role in breathing, swallowing, and speaking, but little is known about the electromyogram (EMG)-force relationship of these muscles. We have measured the peak integrated EMG activity (iEMG) and force of human nasal dilator muscles (NDM) with a custom-designed headpiece that was attached via the forehead and upper lip. The headpiece contains a micromanipulator that holds a rod with a load cell mounted on its tip.