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

This investigation was designed to examine the relationship between breathing 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 and followed by an object lift. Subsequently, in response to an auditory signal the subjects reached forward, grasped and lifted an instrumented object that weighed either 150 g or 1000 g while their fingertip forces and movements were measured. The auditory signal was triggered by airflow in response to four experimental conditions (1) expiratory onset (2) inspiratory onset (3) mid-inspiration and (4) mid-expiration. Five trials for each of the four conditions were completed with each weight. The results revealed that inspiratory time was longer under baseline conditions after the subjects lifted the 150 g object as compared to the 1000 g object. In addition, the response latency and reach duration were significantly slower for the 150 g object compared to the 1000 g object during the experimental trials. These temporal measures were significantly correlated to inspiratory time for three of the four experimental conditions but no significant relationship with expiratory time was found. Lastly, lifting of the object occurred during expiration during most experimental conditions. We conclude that an adaptive process is formulated for both the motor and respiratory system in response to changes in motor output and/or sensory inputs associated with object manipulation, that might manifest itself in the pattern of breathing subsequent to removal of these stimuli. Furthermore, we suggest that motor inputs associated with the initiation of object manipulation interact with the control of respiratory timing so that the motor and respiratory systems are coupled. We speculate that this relationship may ensure that some motor tasks are performed during expiration to take advantage of changes in intrathoracic pressure that assist in postural maintenance during completion of the task.