Conventional biomechanical analyses of human movement have been generally derived from linear mathematics. While these methods can be useful in many situations, they fail to describe the behavior of the human body systems that are predominately nonlinear. For this reason, nonlinear analyses have become more prevalent in recent literature. These analytical techniques are typically investigated using concepts related to variability, stability, complexity, and adaptability. This review aims to investigate the application of nonlinear metrics to assess postural stability. A systematic review was conducted of papers published from 2009 to 2019. Databases searched were PubMed, Google Scholar, Science-Direct and EBSCO. The main inclusion consisted of: Sample entropy, fractal dimension, Lyapunov exponent used as nonlinear measures, and assessment of the variability of the center of pressure during standing using force plate. Following screening, 43 articles out of the initial 1100 were reviewed including 33 articles on sample entropy, 10 articles on fractal dimension, and 4 papers on the Lyapunov exponent. This systematic study shows the reductions in postural regularity related to aging and the disease or injures in the adaptive capabilities of the movement system and how the predictability changes with different task constraints.

The aim of the study was to assess the impact of a vestibular-stimulating exercise regime on postural stability in individuals with visual impairment. The study group consisted of 70 people, including 28 persons (15 female and 13 male) with visual impairment and 42 (21 female and 21 male) without visual impairment. Each individual in the group with visual impairment was medically qualified for a 3-month training program. The research methodology included medical examination, anthropometric tests, and stabilometry tests on a Biodex Balance System SD (BBS). The tests were conducted twice: once before the start of training and again after 3 months of rehabilitation. The group with visual impairment showed significantly worse postural stability results than the control group for most of the stability parameters evaluated (OSI, APSI, and MLSI). Differences were noted between the groups with and without visual impairment for dynamic tests in women and for static tests in men. After training, the two groups showed roughly similar results for the stabilometry test with eyes closed. We conclude that exercises stimulating the vestibular system with head and body movements should be recommended for individuals with visual impairments to achieve better balance retention.

Background:To evaluate the long-term impact of preterm birth on respiratory function in female patients born preterm, we undertook spirometric examinations twice, as they reached the age of puberty, then follow-up examinations of part of the same cohort in adulthood. We sought evidence that preterm birth is correlated with poorer spirometric results into adulthood.Methods:A total of 70 girls (aged 12.2 ± 1.5 years in 1997) who had been born preterm (at 34.7 ± 1.86 weeks, none having experienced bronchopulmonary dysplasia) took part in spriometric examinations in 1997 and again in 1998. Of those, after a gap of 17 years, a group of 12 were successfully recontacted and participated in the 2015 examination as adults (then aged 27.6 ± 2.6 years, born at 34.5 ± 1.92 weeks). We compared spirometric results across the adolescent and adult examinations, and compared the adult results with an adult reference group.Results:The percentage values of FEV1 (forced expiratory volume in 1 s), FVC (forced vital capacity) and MVV (maximal voluntary ventilation) showed significant improvement between the two examinations in the early adolescent period. In adulthood, FEV1%pred (percentage predicted forced expiratory volume in 1 s) showed no statistically significant difference. The mean values of both FVC and FVC%pred (percentage predicted forced vital capacity) for the preterm-born group were lower than for the reference group, but this was not statistically significant. The preterm-born group showed lower values of such parameters as forced expiratory flow at 25–75% of FVC, MEF25 (maximal expiratory flow at 25% of forced vital capacity) and FEV1/FVC as compared with the reference group, but again without statistical significance.Conclusions:(1) A somewhat below-norm level of respiratory parameters among preterm-born girls entering pubescence may attest to continued negative impact on their respiratory system.(2) A significant improvement in their spirometric results 1 year later may indicate that pubescence helps compensate for the earlier negative effect of preterm birth.(3) No significant differences were seen in lung function in preterm-born adults as compared with a reference group of adults, although the preterm-born group did exhibit lower values of all parameters studied and more frequent obstructive disorders.

Exercises stimulating the vestibular organ, such as those described herein, should be a part of efforts to improve balance in older people.

The aim of this study was to analyse transfer of mechanical energy between body segments during the glide shot put. A group of eight elite throwers from the Polish National Team was analysed in the study. Motion analysis of each throw was recorded using an optoelectronic Vicon system composed of nine infrared camcorders and Kistler force plates. The power and energy were computed for the phase of final acceleration of the glide shot put. The data were normalized with respect to time using the algorithm of the fifth order spline and their values were interpolated with respect to the percentage of total time, assuming that the time of the final weight acceleration movement was different for each putter. Statistically significant transfer was found in the study group between the following segments: Right Knee – Right Hip (p = 0.0035), Left Hip - Torso (p = 0.0201), Torso – Right Shoulder (p = 0.0122) and Right Elbow – Right Wrist (p = 0.0001). Furthermore, the results of cluster analysis showed that the kinetic chain used during the final shot acceleration movement had two different models. Differences between the groups were revealed mainly in the energy generated by the hips and trunk.