Introduction. The article describes the study of information entropy in short signals of heart rate and blood pressure rhythmograms at rest and during exercise in middle-aged and elderly patients undergoing rehabilitation. The hypothesis under study is based on the idea that a violation of regulation (quantified by entropy) of continuous noninvasive signals of heart rhythms and blood pressure can serve as a marker of physical condition. Physical fraility is defined as a condition preceding disability that is difficult to recognize in the early stages. The purpose of the study is to improve the diagnosis of the physical aspect of age-related resilience according to the features of the regulatory circulatory systems in middle-aged and elderly patients Material and methods. Two groups of patients undergoing respiratory rehabilitation were examined, middle-aged (45-59 years old) and elderly (60-74 years old) according to the WHO classification. The study of the physical condition was carried out according to the traditional method. Additionally, a spiroarteriocardiorhythmographic (SACR) study was performed at rest and when performing a test with physical activity. Results. The advantages of assessing the regulatory circulatory systems in terms of the randomness of the variability of circulatory parameters compared with the traditional approach are shown. We found that the examined elderly patients before rehabilitation had a higher entropy with continuous measurement of blood circulation indicators in a state of stepwise increasing physical activity. Conclusion. Quantitative assessment of entropy in short-wave signals of blood circulation indicators can become a marker of early regulatory disorders underlying senile asthenia, which will allow assessing the dynamics of rehabilitation effects in elderly people with a higher risk of disability.