Morphofunctional Characteristics of 12- to 14-Year-Old Boys As Dependent on Their Physiological and Chronological Ages

Abstract

Many recent works have testified to the interrelation between sexual maturity and the morphofunctional state of many body systems and the body on the whole [1][2][3][4]. However, in most of these studies, the subjects were adolescents of different physiological ages whose sexual maturity was not taken into account or children at puberty who were not divided by their chronological age; this circumstance makes it difficult to interpret the results. Therefore, this problem requires additional study.Our purpose was to evaluate the level of morphofunctional development of boys with different stages of sexual maturation (from 0 to III) at the chronological age of 14 years and 12-to 14-year-old adolescents with the same sexual maturity level (I). METHODSWe examined 84 boys aged 12-14 years, pupils of a general school in Novosibirsk. The boys belonged to the standard medical group and were not athletes.Our ontogenetic studies were based on longitudinal-transversal sections. The examination was anthropometric [5]: we measured the body length and mass (BL and BM), chest circumference (CC), handgrip and torso muscle strength (HS and TS), and (by the caliper method [6, 7]) deposit fat and calculated the active body mass (ABM) as ABM = BM -(BM × fat (%)/100) [8] and Quetelet's body mass index (QI) as QI = BM (kg)/BL 2 (m 2 ). The maximum muscle endurance (MME) was measured with a hydraulic dynamometer at 75% of the maximum tension [9].Sexual maturity was evaluated by secondary sexual characters [10,11]; vital capacity (VC) was measured with a Spiro-18V water spirometer; the peak inspiratory and expiratory flow rates (PIFR and PEFR) were measured with a PT-1 pneumotachometer with subsequent calculation of the relative indices of the external respiratory function per kilogram body mass. The heart rate (HR) was evaluated at physiological rest and during a standard ergometric step test from a cardiogram recorded according to Butchenko [13]. The rate of recovery processes (the recovery index, RI) was calculated from the HR with regard for the exercise power [14]. The blood pressure (BP) was measured by the Korotkoff auscultation method. Stroke and minute volumes (SV and MV) were calculated from Starr's formula [15]; in addition, total peripheral resistance (PR) was evaluated [16]. We used HR variability analysis [17] to evaluate the autonomic regulation of cardiac performance and tension of control mechanisms during subjects' adaptation to physical exercise. In addition, we calculated the tension index (TI) to characterize the tension of the control systems of the body: TI = AMo/(2 × ∆ X × Mo) [17], where Mo is the mode (the most common value of the cardiac interval), which characterizes the humoral control channel and system functioning level; AMo is the amplitude of the mode (the number of values of intervals that correspond to the mode as a percentage of the total number of intervals analyzed); and ∆ X is the variation range (the difference between the longest and the shortest intervals). We evaluated the index of autonomic ton...