ASSOCIATIONS BETWEEN PHYSICAL LOAD AND CARDIAC BIOELECTRIC ACTIVITY IN RESIDENTS OF THE EUROPEAN NORTH OF RUSSIA

Abstract

Introduction: The leading role in studying adaptation processes is assigned to the analysis of the cardiovascular system activity, myocardial function and its electrical activity, both at rest and during physical load. At the same time, it is important to search for new indicators that characterize the dynamics of the adaptation process. Aim: To study associations between physical activity and the interval-amplitude bioelectric characteristics of the myocardium in residents of the European North of Russia. Methods: Electrocardiograms (ECG) were recorded in 19 healthy female students from Syktyvkar, who were not involved in sports activities. The ECG was recorded at rest and 5 minutes after physical load on a cycle ergometer (1 watt per 1 kg of body weight). Intervalamplitude electrical properties of the myocardium were analyzed on ECG. All the examined were divided into 3 groups depending on resting heart rate. Altogether, 570 cardiac cycles were used for the analysis. Results: The RR interval was 0.95 ± 0.07 s (at low frequency) and 0.63 ± 0.04 s (at high frequency) before physical load and decreased to 0.40 ± 0.03 s and 0.38 ± 0.02 s (p < 0.001) after physical load. Depolarization (RT interval) lasted 0.52 ± 0.02 s (at low frequency) and 0.46 ± 0.01 s (at high frequency) before physical load. After physical load there was a decrease to 0.38 ± 0.03 s at low frequencies and up to 0.36 ± 0.02 s at high frequency (p < 0.001). RD amplitudes before physical load were 1.47 ± 0.10 mV and 1.50 ± 0.12 mV, after physical load 1.16 ± 0.16 mV and 1.1 ± 0.17 mV (at low frequency and high frequency): average decrease by 20% (p < 0.001). Variability of RD amplitudes before and after physical load wais ±0.50 mV. Repolarization (TR segment) before physical load was 0.43 ± 0.07 s (at low frequency) and 0.17 ± 0.04 s (at high frequency F). After physical load it decreased to 0.02 ± 0.01 s (at low frequency and high frequency) (p < 0.001). Conclusions: The decrease in the duration of the PP, RT and TR segments after the load depends on their initial value before the load.