Interactions of breathing with the postural regulation of the fingers

Objectives: The present study was performed to detect the interactions between breathing and the postural motor control of the fingers. A previous study revealed a scattering in the intraindividual motor responses which resembled a grouping. It is hypothesized to result from the influence of breathing. Methods: Torque impulses and torque steps at two intensities were applied to 17 healthy volunteers, to the II–IV fingers of their right hand. The subjects had to compensate for these additional torque loads that were triggered by a breathing-related signal and elicited at 4 different moments within a breath. Results: We demonstrated mutual influences between breathing and the regulation of finger posture. The reaction to a torque load was faster at the beginning of inspiration but more precise when the torque load was applied in mid-expiration. The motor response to torque loads was accompanied by changes in the breathing time course, particularly when the torque load was elicited during inspiration. The effects were most pronounced when torque steps were applied. The intensity of torque loads had no significant influence. Additionally, we observed that the respiratory phase-transitions often coincided with the end of the applied torque steps. Conclusions: The results correspond well with the interactions existing between breathing and single or rhythmical movements. Further investigations of motor functions should consider this interdependence with breathing.