Non-Linear and Linear Measures Reflect Different Effects of Breathing as a Perturbation on Postural Control

Purpose: The aim of the study was to investigate the effects of breathing as a perturbation for postural control during quite standing.

Methods: Six elderly participants (1 male, 5 female) were recruited for the study. Participants stood for 60 seconds on a force platform to complete four different conditions: 1) breathing normally (NB); 2) breathing with mainly chest movement (CB); 3) breathing mainly using abdominal muscles (AB); and 4) paying close attention to the breathing related movements without conscience control of the movement (FB). CB and AB conditions were aided with visual feedback with their own breathing patterns. The trajectories of center of pressure (COP) movement were collected at 100 Hz. Traditional measures, 95% area of COP (95%Area) & average velocity of COP movement (Vavg), and non-linear measures, approximate (ApEnx) and sample (SampEnx) entropy in the anterior-posterior (x-direction), were calculated for each participants during each condition.

Results: The average age (71 ± 8 years old), height (163 ± 8 cm), body mass (82 ± 25 kg). Results shown in Figure 1. Comparing to NB, CB and AB serves as perturbation that increased the magnitudes of both the linear and non-linear measures with greater amplitudes. The FB reversed the trends observed by linear measures but continue the increasing trends with the non-linear measures.

Conclusions: The effects of the mechanical perturbation (CB and AB) to postural control influence the linear and non-linear measures in a similar trend, but differential effects of the mental concentration can be revealed by the different results of the two measurement methods.