<bold>Purpose.</bold> The aim of the paper was to determine the effect of respiration on body balance in quiet standing. <bold>Basic procedures.</bold> Postural performance during quiet standing was compared in 37 young healthy subjects in two trials on a force plate: first with natural breathing, and then with accelerated high-volume breathing at the rate of 1 Hz. Each trial included 20 s quiet standing with eyes open, and the center of pressure (COP) was recorded with the sampling rate of 20 Hz in both anterior-posterior (AP) and mediallateral (ML) planes. Based on the recorded signals the COP dispersion measures and postural frequency were calculated. <bold>Main findings.</bold> The forced respiration contributed significantly to the increase in all COP stability measures in the AP plane: dispersion (p < 0.01), range (p < 0.001) and mean velocity and frequency (p < 0.00001). In the ML plane only mean velocity (p < 0.001) and frequency (p < 0.01) were affected. <bold>Conclusions.</bold> In view of the evidence provided by other authors that stress tests increase the amplitude- and frequency-based stability measures, our results indicate that the contribution of natural accelerated breathing after strenuous physical exercise will bias the results of stabilographic studies, rendering them worthless in understanding the role of neuromuscular fatigue in stability deterioration. Such studies must use data collected after the respiration returns to normal rate. However, if the study aims at overall assessment of postural stability post-fatigue, the postural testing may be performed immediately after the stress test.
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