Relationship between physical exercise type and fatigue quantified through HRV, CK, and blood lactate

Abstract

Athletes are exposed to high-intensity loads to promote athletic performance, however, the effects are not evaluated appropriately. This study investigates the effects of four types of exhaustion exercises on Heart Rate Variability (HRV) and Poincaré features (SD1: Standard deviation 1and SD2: Standard deviation 2), Creatine Kinase (CK) and blood lactate concentrations as biomarkers of fatigue. To achieve this purpose, 10 healthy volunteers were exposed to exhaustive exercise using isotonic, isometric, aerobic and anaerobic fatigue protocols. HRV Poincaré features, standard deviation of instantaneous beat-to-beat R-R interval variability (SD1) and standard deviation of continuous long-term R-R interval variability (SD2) variables were collected. Fatigue was tested through the sympathetic stress index (SS), the index sympathetic/parasympathetic index (S/PS) and the root Mean Square of the Successive Differences (rMSSD) as parasympathetic index. Blood samples were collected at the beginning and at the end of the exercises to determine CK and lactate. The SD1 decreased in each exercise protocol, while the SS and S/PS increased. Lactate and CK increased at the end of each protocol and correlated with SD1 and S/PS. HRV, CK, and lactate are acute markers to detect fatigue, are sensitive to the type, duration, and intensity of exercise, being HRV a novel noninvasive marker, simple and useful for sports coaches and athletes.