[Significance of chronotropic exertion effects on the heart in diagnosing physical fitness in children practising swimming].

Regarding the peculiar character of exercise adaptation in developmental age, two questions have been stated; in what degree heart rate (HR) changes after physical effort reflect and diagnose the physical fitness in children and if these values can be the base of indirect method of maximal oxygen intake (VO2max). The practical problem was to choose the method, which could make the data for the comparative analysis of the heart's chronotropic reaction in children practising swimming professionally and in non-practising ones possible to obtain. The research method should not be connected with excessive workload for children. The heart's chronotropic reaction has been thoroughly analysed in different phases of submaximal progressive effort, according to the methods specific for the PWC170 index estimation; its diagnostic value would determine its differentiation in the age groups of swimmers and non-practising children and correlation between its indexes and real oxygen efficiency estimated using maximal oxygen intake values obtained in direct method (VO2maxEZ). 186 girls and 225 boys aged 10 to 15, practicing systematically since the 10th year of life, were investigated. During six years of the study 1308 exercise trials have been performed, including 654 tests with submaximal workload specific for the PWC170 index estimation (Physical Work Capacity), and 654 spiroergometric tests (TSE) with maximal workload and direct measurement of oxygen intake. Data obtained from the test with submaximal workload were compared with those noted in the same age groups of non-practicing children (246 girls and 256 boys), who formed the control groups for male and female swimmers. Those children from primary school had never practised any organized form of sport apart from obligatory physical exercises at school. Comparative analysis of physical efficiency indexes followed the estimation of basic morphologic features in studied children (body weight, fat-free body weight, body height). The heart's chronotropic reaction has been characterized in a traditional way as PWC170 and PWC150 indexes; it has been also thoroughly analyzed during following stages of the test estimated by workload changes, as well as the resultant for the whole workload dynamics of the HR changes, which has characterized the physiologic chronotropic expense of one watt of the workload applied. In the same time relationship between values obtained directly before the beginning of the exercises (HRW) have been analyzed. Although it has been found that discussed PWC indexes can differentiate in mean falues the groups of practising and non-practising children in the same age, but in significant percentage their values were nearing in both groups; it has been distinctly shown in the value distribution in percentile scores (Fig 1). This situation undoubtedly reduces the diagnostic advantages of the discussed indexes. HRW values have influenced the course of the test and its final result, and especially PWC indexes (significant in some groups of children), which has been emphasized. In the research a problem is discussed: in what degree the changes of the heart rate can describe the general physical fitness of people studies. Comparative analysis of the PWC and TSE tests performed in swimmers show no relationship between physical oxygen efficiency and values of PWC170 and PWC150 indexes. In the longitudinal research the PWC170 test results have significantly fluctuated during progressively increasing values of maximal oxygen intake measured directly, which has been pointed out. Maximal oxygen intake should be evaluated critically on the base of the heart's chronotropic reaction after exercise in children. It seems that more reliable in estimating the exercise adaptation is to describe the heart's chronotropic reaction using its direct indexes. It is possible to use PWC170 results, but it is necessary to regard the initial HR values when starting the exercise.