Modeling the basin of attraction as a two-dimensional manifold from experimental data: applications to balance in humans.

We present a method of modeling the basin of attraction as a three-dimensional function describing a two-dimensional manifold on which the dynamics of the system evolves from experimental time series data. Our method is based on the density of the data set and uses numerical optimization and data modeling tools. We also show how to obtain analytic curves that describe both the contours and the boundary of the basin. Our method is applied to the problem of regaining balance after perturbation from quiet vertical stance using data of an elite athlete. Our method goes beyond the statistical description of the experimental data, providing a function that describes the shape of the basin of attraction. To test its robustness, our method has also been applied to two different data sets of a second subject and no significant differences were found between the contours of the calculated basin of attraction for the different data sets. The proposed method has many uses in a wide variety of areas, not just human balance for which there are many applications in medicine, rehabilitation, and sport.

Type of delivery is not affected by light resistance and toning exercise training during pregnancy: a randomized controlled trial.

OBJECTIVE: We examined the effect of light-intensity resistance exercise training that is performed during the second and third trimester of pregnancy by previously sedentary and healthy women on the type of delivery and on the dilation, expulsion, and childbirth time. STUDY DESIGN: We randomly assigned 160 sedentary women to either a training (n=80) or a control (n=80) group. We recorded several maternal and newborn characteristics, the type of delivery (normal, instrumental, or cesarean), and dilation, expulsion, and childbirth time. RESULTS: The percentage of women who had normal, instrumental, or cesarean delivery was similar in the training (70.8%, 13.9%, and 15.3%, respectively) and control (71.4%, 12.9%, and 15.7%, respectively) groups. The mean dilation, expulsion, and childbirth time did not differ between groups. CONCLUSION: Light-intensity resistance training that is performed over the second and third trimester of pregnancy does not affect the type of delivery.

Correlations between the blood pressure and other health variables in Spanish adolescents.

The aim of this paper was to study the correlations between blood pressure and other health variables in Spanish adolescents. 204 boys and 270 girls (aged 13-17 years, with written parental consent,) from 18 private and 17 public educative centers from 16 of 21 districts of the city of Madrid, constituted the representative sample. 12.7% of the boys and 35.6% of the girls were inactive or sedentary. Socioeconomic status significantly determined the physical activity of girls, especially in the age group 16-17 years. The tobacco consumption by girls was significantly greater than by boys. A significant inverse relation of tobacco consumption with physical activity was found for boys. Among the girls, 47.4% were lightly overweight to obese as opposed to 14.7% of boys. A significant association between adiposity and physical activity in the girls was observed. The averages for the systolic/diastolic blood pressure were 125.6/71.3 mm Hg in boys and 118/69.4 mm Hg in girls. A significant relation between gender and systolic blood pressure was found. A relation between physical activity and diastolic blood pressure for boys was observed (69.9 mm Hg for active or very active and 74.1 mm Hg for moderately active to sedentary). The lack of existing relations between blood pressure and others variables support the hypothesis that these variables require a longer-term to become obvious cardiovascular risk factors. We believe, therefore, that girls and those from lower socioeconomic status should receive high-priority attention concerning health-related habits.

Geometry and transport in a model of two coupled quadratic nonlinear waveguides.

This paper applies geometric methods developed to understand chaos and transport in Hamiltonian systems to the study of power distribution in nonlinear waveguide arrays. The specific case of two linearly coupled chi((2)) waveguides is modeled and analyzed in terms of transport and geometry in the phase space. This gives us a transport problem in the phase space resulting from the coupling of the two Hamiltonian systems for each waveguide. In particular, the effect of the presence of partial and complete barriers in the phase space on the transfer of intensity between the waveguides is studied, given a specific input and range of material properties. We show how these barriers break down as the coupling between the waveguides is increased and what the role of resonances in the phase space has in this. We also show how an increase in the coupling can lead to chaos and global transport and what effect this has on the intensity.