© VIBROMECHANIKA. JOURNAL OF VIBROENGINEERING. 2007 JULY/SEPTEMBER, VOLUME 9, ISSUE 3, ISSN 1392-8716 42 292. Evaluation components of the heart rate kinetics for assessment cardiac adaptation during rehabilitation J. Brožaitienė 1 , E. Bovina Institute Psychophysiology and Rehabilitation c/o Kaunas University of Medicine Vydūno al. 4, LT-00135 Palanga, Lithuania Fax. +37046030014, Tel. +37046030023 1 E-mail: jbro@ktl.mii.lt (Received 04 June 2007, accepted 18 June 2007) Abstract. The purpose of the study was assessment of the cardiovascular adaptation to the workload and physical training by analysis of the heart rate kinetics and dynamics of power spectrum components in healthy subjects and ischemic heart disease patients during rehabilitation. The contingent of study was 20 healthy subjects and 97 patients post-myocardial infarction (74 without chronic heart failure and 23 with chronic heart failure symptoms). Multistage bicycle ergometry or spiroergometry and computerized analysis of heart rate variability during active orthostatic, symptom-limited workload tests and recovery period after test were performed. The rhythmogram at 50W of the workload, and during bicycle (Kettler) training and recovery period was analyzed and the time constant (τ) of the exponential function (by using Proni method), coefficients of amplification, rapidity as well as heart rate (HR) power spectral components (σVLF, σLF, σHF) were evaluated. Heart rate kinetics response time constant to the low-level (τ 50W ) workload (30.3 vs. 19.3 s) and during recovery period (40 vs. 45.6 s) was delay in post-myocardial infarction patients, especially in those with CHF and low physical capacity as compared with healthy subjects. Heart rate responses (τ 50W ) correlated with baseline HR autonomic control components (σLF, r=-0.25, ∆RR B %, r=-0.24, RR B , r=0.23,) and with physical capacity (r=-0.30). In CHF patients the delay HR response to the workload and during recovery correlated with expressed ventilatory response (VE/VCO 2 , r=0.60) in this group. Positive dynamic of HR kinetics components (τ=37.1 vs. 34.6 s) and power spectrum characteristics after low intensity bicycle training procedure and during recovery (τ=42.4 vs. 39.9 s) period was observed. The faster HR reaction to the physical stressor after 3-weeks bicycle training correlated with positive dynamics of σHF (r=-0.35). The HR power spectrum components during bicycle training changed favorably (σVLF, 15.2 vs. 16.3 ms; σLF, 8.2 vs. 9.4 ms; σHF, 8.8 vs. 9.4 ms) too. Conclusions. Analysis of the heart rate kinetics components and power spectrum data during exercise provides a new possibility evaluation of the cardiac adaptation to the workload and physical training procedures in ischemic heart disease patients during rehabilitation. Keywords: heart rate kinetics components, power spectrum analysis, submaximal exercise, physical rehabilitation, post- myocardial infarction patients, healthy subjects. Introduction Adaptation of cardiovascular system to the physical stress is proceeding throughout increasing of the heart rate, cardiac output, oxygen uptake and blood pressure. Heart rate (HR), as an integral index, reflect the cardiovascular functional status [1, 2, 3], fast reaction to stressors by autonomic regulation [4, 5, 6] and prognosis [1, 7, 8]. HR and heart rate variability (HRV) are key determinants of the cardiovascular function and its autonomic nervous control. Analysis of the heart rate kinetics and variability during physical workload has some methodical difficulties, because of non-stationary of the process. It is known that during beginning of the workload the HR rapidity (which adequate 30% of oxygen uptake) is proceeding by exponential function, which consists of fast and slow components. It is suspected, that the fast component, with time constant about 10 s, is based on the withdrawal of the