Age-Related Changes in Standing Balance in Preschoolers Using Traditional and Nonlinear Methods

Nonlinear dynamics of postural control system under visual-vestibular habituation balance practice: evidence from EEG, EMG and center of pressure signals

Human postural control system is inherently complex with nonlinear interaction among multiple subsystems. Accordingly, such postural control system has the flexibility in adaptation to complex environments. Previous studies applied complexity-based methods to analyze center of pressure (COP) to explore nonlinear dynamics of postural sway under changing environments, but direct evidence from central nervous system or muscular system is limited in the existing literature. Therefore, we assessed the fractal dimension of COP, surface electromyographic (sEMG) and electroencephalogram (EEG) signals under visual-vestibular habituation balance practice. We combined a rotating platform and a virtual reality headset to present visual-vestibular congruent or incongruent conditions. We asked participants to undergo repeated exposure to either congruent (n = 14) or incongruent condition (n = 13) five times while maintaining balance. We found repeated practice under both congruent and incongruent conditions increased the complexity of high-frequency (0.5-20 Hz) component of COP data and the complexity of sEMG data from tibialis anterior muscle. In contrast, repeated practice under conflicts decreased the complexity of low-frequency (<0.5 Hz) component of COP data and the complexity of EEG data of parietal and occipital lobes, while repeated practice under congruent environment decreased the complexity of EEG data of parietal and temporal lobes. These results suggested nonlinear dynamics of cortical activity differed after balance practice under congruent and incongruent environments. Also, we found a positive correlation (1) between the complexity of high-frequency component of COP and the complexity of sEMG signals from calf muscles, and (2) between the complexity of low-frequency component of COP and the complexity of EEG signals. These results suggested the low- or high-component of COP might be related to central or muscular adjustment of postural control, respectively.

The effects of Tai Chi on standing balance control in older adults may be attributed to the improvement of sensory reweighting and complexity rather than reduced sway velocity or amplitude

Introduction

Tai Chi has proved to be an effective therapy for balance performance and cognition. However, non-consistency exists in the results of the effect of Tai Chi training on standing balance control in older adults. This study aimed to use traditional and non-traditional methods to investigate the effect of Tai Chi on standing balance in older adults.

Methods

Thirty-six Tai Chi practitioners (TC group) and thirty-six older adults with no Tai Chi practice (control group) were recruited in this study. A Nintendo Wii Balance Board was used to record the center of pressure (COP) during standing balance over 20 s in the condition of eyes closed with three repetitions. The wavelet analysis, multiscale entropy, recurrence quantification analysis, and traditional methods were used to evaluate the standing balance control in the anterior-posterior (AP) and mediolateral (ML) directions.

Results

(1) Greater sway mean velocity in the AP direction and sway Path length were found in the TC group compared with the control group; (2) lower Very-low frequency band (0.10-0.39 Hz) and higher Moderate frequency band (1.56-6.25 Hz) in the AP and ML directions were found in the TC group compared with the control group; (3) greater complexity index (CI) and lower determinism (DET) in the AP and ML directions were observed in the TC group compared with control group; (4) greater path length linked with smaller Very-low frequency band in the AP and ML directions and higher Moderate frequency band in the AP direction in both groups; (5) greater path length linked with lower DET and higher CI in the AP direction only in the TC group.

Conclusion

Long-term Tai Chi practice improved sensory reweighting (more reliance on the proprioception system and less reliance on the vestibular system) and complexity of standing balance control in older adults. In addition, greater sway velocity may be as an exploratory role in standing balance control of TC older adults, which correlated with greater complexity, but no such significant relationship in the control group. Therefore, the effects of Tai Chi practice on standing balance control in older adults may be attributed to the improvement of sensory reweighting and complexity rather than reduced sway velocity or amplitude.

Age and gender differences in static and dynamic balance of Chinese preschool children

Objectives: Balance is a crucial ability of early age, but there is conflicting evidence with regard to age and gender differences in preschool children's balance ability. Additionally, there are several tools available to measure balance, yet, wide variation in their use has restricted the capacity to synthesize the reference values. Therefore, the primary purpose of this study was to investigate the balance ability of preschool-aged children and determine how it is moderated by age and gender. The analysis pertained to determining whether different testing methods affect the results of static or dynamic balancing ability to provide a basis for normative balance ability data for healthy boys and girls between 3 and 6 years of age. Method: Six hundred and nineteen preschool children (296 boys and 323 girls) aged 3-6 years participated in the study. The static balance (SB) was assessed with children standing on one leg (OST) and in a tandem stance (TS) with respect to time. The balance beam test (BBT) and functional reach test (FRT) were used to evaluate dynamic balance (DB) by measuring the time spent and the distance reached, respectively. Result: The results revealed significant differences in OST with respect to gender (η2 = 0.037, p < 0.001), TS (η2 = 0.026, p < 0.001) and FRT (η2 = 0.016, p = 0.002); the girls performed better than boys on most balance tests except on BBT (η2 = 0.000, p = 0.596). Age had positive effects on the static and dynamic balance performance on the OST (η2 = 0.336, p < 0.001), TS (η2 = 0.205, p < 0.001), BBT (η2 = 0.367, p < 0.001) and FRT (η2 = 0.392, p < 0.001). Older children performed better than their younger counterparts. No significant interactions between age groups and sex were found. Conclusion: This study revealed that static and dynamic balance stability in preschool-aged children was affected by gender and age. Gender dimorphism is present in preschool children, older girls displayed better postural stability than boys, and balance performance improved with age. In addition, the study provides age- and gender-specific balance performance reference values for preschool children across multiple methods, which can be used to monitor static and dynamic balance development.