The purpose of the work is to study the time preferences of students performing daily tasks during distance learning and to determine if such preferences depend on sex and the year of study. In the absence of social regulation, the daytime and nighttime activity of students corresponded to the distribution of chronotypes that typifies a northern region, with arrhythmic and evening types prevailing but the morning bio-rhythmic stereotype having a minimal representation. With no ‘master timer’ in distance learning, students demonstrated pronounced sex differences in the daily dynamics of performance. Young females had maximum performance during the day and minimum performance at night, which corresponds to the most common type. Young males were observed to have several ascents in their performance during the 24-hour period. First-year and second-year students’ learning behavior was less synchronized with the day-night cycle. The wavelet analysis found insignificant four to five hourrhythmic fluctuations that occurred in the evening hours, during the period of students’ high educational performance.

The article presents the main characteristics of the Syndrome of undiff erentiated connective tissue dysplasia, refl ecting the essence of this problem in the system of public health, in particular children and adolescents. The mechanism of the formation of this condition and its clinical manifestations are consecrated.

Abstract. In connection with the spread of undifferentiated forms of connective tissue dysplasia (UCTD) in unfavorable climatogeographic and environmental conditions, it seems relevant to assess the impact of organogenesis disorders on physical development in schoolchildren living in the northern region. Based on the foregoing, the purpose of this study was to study the relationships and interdependencies of the components of physical development and somatometric indicators in children of the northern region with phenotypic signs of connective tissue dysplasia. Anthropometric indicators were revealed that can be used for express diagnostics of the level of physical development in children with UCTD these are the length of the legs, the thickness of the skin-fat fold on the front surface of the shoulder and the interorbital-circumferential index. When assessing covariants such as age and sex, there is a correlation of clusters of long-length values with age, the relationship of the thickness of the skin-fat folds with the floor, and the parameters assessing changes in the cerebral and facial skull, such as: face width, head circumference and interorbital-circumferential index are associated with both sex and with age. The influence of posture disorders on the studied components of physical development is manifested by higher growth in children with flat and round-curved backs, a decrease in the thickness of skin-fat folds and head size with a round and round-curved back. Thus, for a comparative analysis of gender and age differences in the level of physical development in children with UCTD, it is necessary to take into account the dynamics of interdependent anthropometric indicators and indices, taking into account postural disorders.

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