Is body balance more perturbed by respiration in seating than in standing posture?

The perturbing influence of respiration on balance was studied in sitting and standing subjects. The pneumograms and displacements of the centre of pressure of 10 normal subjects were recorded during quiet breathing, deep breathing and apnoea. The usual stabilometric parameters were measured, and a power spectrum density and time-locked averaging were used. The sway path was longer in seated subjects than in standing ones, suggesting that instantaneous compensatory phenomena are less efficient. The respiratory component of the sway path was larger in seated (0.16) than in standing subjects (0.09). It is concluded that respiration is a significant input for postural control, and that sitting entails less instantaneous steadiness. The concept of respiratory synergy is discussed.