To evaluate postural control and performance in subjects with Down syndrome (SwDS), we measured postural sway (COP) in quiet stance in four 20-second tests: with eyes open or closed and on hard or foam surface. Ten SwDS and eleven healthy subjects participated, aged 29.8 (4.8) and 28.4 (3.9), respectively. The time-series recorded with the sampling rate of 100 Hz were used to evaluate postural performance (COP amplitude and mean velocity) and strategies (COP frequency, fractal dimension and entropy). There were no intergroup differences in the amplitude except the stance on foam pad with eyes open when SwDS had larger sway. The COP velocity and frequency were larger in SwDS than controls in all trials on foam pad. During stances on the foam pad SwDS increased fractal dimension showing higher complexity of their equilibrium system, while controls decreased sample entropy exhibiting more conscious control of posture in comparison to the stances on hard support surface. This indicated that each group used entirely different adjustments of postural strategies to the somatosensory challenge. It is proposed that the inferior postural control of SwDS results mainly from insufficient experience in dealing with unpredictable postural stimuli and deficit in motor learning.

It is argued that elite athletes often demonstrate superior body balance. Despite the apparent significance of perfect balance ability in volleyball, little is known about the specific nature of postural control adjustments among first-rate volleyball competitors. This study compared postural performance and strategies in quiet stance between world vice-champions and young, healthy, physically active male subjects. The center-of-pressure (COP) signals recorded on a force plate were used to compute several measures of sway. In both axes of movement, athletes had lower COP range, but not its standard deviation and higher COP speed and frequency than controls. These findings indicate that postural regulation in athletes was more precise and less vulnerable to external disturbances which support optimal timing and precision of actions. Postural strategies in athletes standing quietly were similar to those exhibited by non-athletes performing dual tasks. It demonstrates a significant effect of sport practice on changes in postural control. In anterior–posterior axis, athletes displayed a much higher COP fractal dimension and surprisingly lower COP–COG frequency than controls. This accounts for their high capacity to use diversified postural strategies to maintain postural stability and significantly reduced the contribution of proprioception to save this function for carrying out more challenging posture-motor tasks.

Background: The aim of this study was to compare the postural control of the Poland national women’s volleyball team players with a control group of non-training young women. It was hypothesized that volleyball players use a specific balance control strategy due to the high motor requirements of their team sport. Methods: Static postural sway variables were measured in 31 athletes and 31 non-training women. Participants were standing on a force plate with eyes open, and their center of pressure signals were recorded for the 20s with the sampling rate of 20 Hz in the medial-lateral (ML) and anterior-posterior (AP) planes. Results: In both AP and ML planes, athletes had lower range and higher fractal dimension of the COP. They had also higher peak frequency than control group in the ML plane only. The remaining COP indices including variability, mean velocity and mean frequency did not display any intergroup differences. Conclusion: It can be assumed that due to the high motor requirements of their sport discipline Polish female volleyball players have developed a unique posture control. On the court they have to distribute their sensory resources optimally between balance control and actions resulting from the specifics of the volleyball game. There are no clearly defined criteria for optimal postural strategies for elite athletes, but they rather vary depending on a given sport. The results of our research confirm this claim. Trial registration: The tests were previously approved by the Bioethical Commission of the Chamber of Physicians in Opole. (Resolution No. 151/13.12.2007). This study adheres to the CONSORT guidelines.

Aging is associated with degenerative changes in articular surfaces leading to quantitative and qualitative impairment of joint motion. Therefore, the aim of this study is to evaluate an age-related quality of the patellofemoral joint (PFJ) motion in the vibroarthrographic (VAG) signal analysis. Two hundred and twenty individuals were enrolled in this study and divided into five groups according to age. The VAG signals were collected during flexion/extension knee motion using an acceleration sensor and described using four parameters (VMS, P1, P2, andH). We observed that values of parameters VMS, P1, and P2 increase in accordance with the age, butHlevel decreases. The most significant differences were achieved between the youngest and the oldest participants’ groups. Moreover, we show that parameters VMS, P1, and P2 positively correlate with age, contrary to negatively associatedHparameter. Our results suggest that the impairment of joint motion is a result of age-related osteoarticular degenerative changes.