Journal of Applied Physiology, Vol 55, Issue 5 1397-1402, Copyright © 1983 by American Physiological Society
Effect of threshold loads on voluntary control of slow and rapid inspiratory movements
L. J. Folinsbee, J. A. Gliner and S. M. Horvath
The purpose of this study was to examine the hypothesis that voluntarily
produced inspiratory movements are preplanned. Subjects performed both
rapid (0.5 s) and slow (2.0 s) voluntary inspirations to a target volume of
50% of their inspiratory capacity under two conditions: 1) normally
unloaded with random loading; and 2) normally loaded with random unloading.
The load was a 10 cmH2O threshold load. When the load was unexpectedly
applied, the subjects undershot the target volume by 397 ml (fast) and 284
ml (slow). When the load was unexpectedly removed, the subjects overshot
the target volume by 303 ml (fast) and 224 ml (slow). The duration of
inspiration did not change significantly. These observations are consistent
with an "impulse-timing" model of preplanned voluntary movement, which
incorporates reflex modification of the movement to compensate for loads
which may be added or removed.
