Prognostic potential of exercise cardiac rhythmogram during the early adaptation period

Aim. The aim of this article is to determine variability of cardiac rhythmogram under the stress test during the early adaptation period (EAP) to reveal prognostic markers of tolerance to physical load. Materials and methods. We studied two groups of relatively healthy people aged 18-22 years (34 persons in each group). The first group consisted of the people involved in sports, and the second group comprised the people not involved in sports. We performed a maximal ergometer test according to an individual protocol. We applied mathematical modeling to CRG obtained. M markers for CRG during the early adaptation period were matched (Spearman) with individual load and recovery figures. We performed an inter-group comparison (Mann-Whitney). Results. The variability of CRG during the early adaptation period has characteristics of the entire exercise period and is connected with individual tolerance to physical load. M markers for CRG reflect peculiarities of the entire time series and can be used to study variability and relations with other adaptation mechanisms. EAP minute models allowed us to reveal its critical stages: maximal variability (1-2 min) and stability (3 min); maximal variability speed (1 min), pronounced speed reduction (2 min), minimal speed (3 min). The last (3) minute of EAP in the second group reflects most accurately the limit of individual tolerance to physical load. Groups differ significantly from each other in terms of the maximal level and chronotropic parameters of tolerance, starting time and speed of CRG changes. At the same time, for the people not involved in sports, M markers for CRG reflect individual tolerance in the same way as average and maximal HR values determined for the entire exercise period. For athletes, the present markers determine maximal tolerance to a less extent but prove tolerance quality. Conclusion. M markers for CRG revealing characteristics and peculiarities of chronotropic adaptation can be used to study and forecast physical endurance and fitness and to prevent physical overexertion in the people involved in sports. For the people not involved in sports, it helps to estimate both health state and disturbances of adaptation processes.