Sex-Specific Dependence of Linear and Nonlinear Postural Control Metrics on Anthropometrics During Clinical Balance Tests in Healthy Young Adults.

CONTEXT:: Previous work suggests that balance behavior is a sex-dependent, complex process which can be characterized by linear and nonlinear metrics. While a certain degree of center of pressure variability may be expected based on sexual dimorphism, there is evidence to suggest that these effects are obscured by potential interactions between sex and anthropometric factors. To date, no study has accounted for such interactive effects using both linear and nonlinear measures.

OBJECTIVE:: This investigation sought to analyze interactive models featuring sex, height, and weight as predictors of linear and nonlinear aspects of postural control.

DESIGN:: Cross-sectional study.

SETTING:: Controlled labarotory.

PARTICIPANTS:: Twenty-six males (23.80 ± 3.44 years, 177.87 ± 6.44 cm, 81.70 ± 10.80 kg) and 28 females (21.14 ± 2.03 years, 169.57 ± 8.80 cm, 64.48 ± 8.86 kg) were sampled from a healthy university population.

MAIN OUTCOME MEASURES:: Linear (range [RNG], velocity [VEL], standard deviation [SD]) and nonlinear (detrended fluctuation analysis [DFA] scaling exponent, multivariate multiscale sample entropy [MMSECI]) summary metrics of center of pressure (COP) time series.

PROCEDURE:: Participants stood on a force plate for 20-sec. in three conditions: Double (D), Single (S), and Tandem (T) Stance. Data for each stance condition were analyzed using regression models with interaction terms for sex*height and sex*weight. In D, weight had a positive, significant main effect on VELy, MMSECId, and MMSECIv. In males, height was observed to have a positive effect on SDy (S), RNGy (S), and RNGx (T); and a negative effect on MMSECIv (T). In females, weight was observed to have a positive effect on SDy and VELx (both T).

CONCLUSIONS:: Our findings suggest that men and women differ with respect to certain linear and nonlinear aspects of balance behavior, and that these differences may reflect sex-specific behavioral patterns in addition to effects related to sexual dimorphism.