Respiratory components of human postural sway.

The effects of respiration on postural sway in normal human subjects was studied using averaging and spectral techniques. During voluntarily paced respiration a substantial proportion of sway was found to result from respiratory activity. The magnitude of the respiratory contribution to sway was approximately constant over the normal range of respiratory rates and linearly related to respiration amplitude. Respiration evoked similar changes in reaction torque in seated subjects. These results indicate that body movements associated with paced respiration are an important disturbance to the postural control system. Furthermore, these disturbances are not reduced by compensatory movements of the hip as has been suggested by others.