Adaptive and dynamic control of respiratory and motor systems during object manipulation

This investigation was designed to examine the relationship between breathi ng and prehension movements during object manipulation. Seated subjects (n= 12) wore a facemask that was attached to a pneumotachometer which measured airflow. Initially, subjects completed baseline trials that were preceded a nd followed by an object lift. Subsequently, in response to an auditory sig nal the subjects reached forward, grasped and lifted an instrumented object that weighed either 150 g or 1000 g while their fingertip forces and movem ents were measured. The auditory signal was triggered by airflow in respons e to four experimental conditions (1) expiratory onset (2) inspiratory onse t (3) mid-inspiration and (4) mid-expiration. Five trials for each of the f our conditions were completed with each weight. The results revealed that i nspiratory time was longer under baseline conditions after the subjects lif ted the 150 g object as compared to the 1000 g object. In addition, the res ponse latency and reach duration were significantly slower for the 150 g ob ject compared to the 1000 g object during the experimental trials. These te mporal measures were significantly correlated to inspiratory time for three of the four experimental conditions but no significant relationship with e xpiratory time was found. Lastly, lifting of the object occurred during exp iration during most experimental conditions. We conclude that an adaptive p rocess is formulated for both the motor and respiratory system in response to changes in motor output and/or sensory inputs associated with object man ipulation, that might manifest itself in the pattern of breathing subsequen t to removal of these stimuli. Furthermore, we suggest that motor inputs as sociated with the initiation of object manipulation interact with the contr ol of respiratory timing so that the motor and respiratory systems are coup led. We speculate that this relationship may ensure that some motor tasks a re performed during expiration to take advantage of changes in intrathoraci c pressure that assist in postural maintenance during completion of the tas k. (C) 2000 Elsevier Science BN. All rights reserved.