A Comprehensive Approach To The Center Of Pressure Differences Between Yoginis And Controls

Abstract

Standard measures such as root mean square (RMS) and mean power frequency (MPF) adequately examine the magnitude of the center of pressure (COP), while nonlinear measures examine the structure of the COP time series. Combining these measures provides a comprehensive analysis of balance control (e.g. comparison of balance of dancers and track athletes, Schmit, Regis, and Riley, 2005). Increased COP amplitude could be due to decreased balance skills or increased exploratory behavior; nonlinear analyses can help differentiate between these interpretations. We expect that yoga practitioners will demonstrate different balance strategies when compared to controls. PURPOSE: To compare balance of yoginis and controls with traditional measures and non linear measures of COP. METHODS: Twenty females participated (27.9 ± 11.48 yrs.), ten yoginis and ten controls. Two randomly-presented focus conditions were observed (1) no instruction, where the participant stood quietly, (2) external fixation, where the participant was asked to focus on an × placed approximately three feet in front of them on the floor. Subjects stood either on two legs or one leg. RESULTS: The results for the anterior posterior sway direction are reported. No three way interactions (group × leg × vision) or two way interactions (group × leg; group × vision; leg × vision) were observed for the standard or the nonlinear measures. The standard measures revealed main effects for RMS for leg and vision conditions (p<.01 leg and p<.01 vision) as well as for MPF for leg condition (p<.01). The nonlinear measures revealed main effects for entropy across groups (p<.01), percent recurrence and percent determinism for the leg condition (p<.01). CONCLUSION: The magnitude and the frequency of the COP measure was not different across the two groups, however, the yoga group COP was less chaotic (decreased entropy) and had trends of increased noise (decreased percent recurrence). These changes are consistent with increased behavioral flexibility. A more complete understanding of postural control was observed when linear and non-linear measures were combined.