Monitoring Heart Rate Variability As A Biomarker Of Fatigue In Young Athletes

Purpose: Many high performance and especially top athletes are still at risk or suffer from total fatigue. Therefore, sports science seeks to develop an objective, sensitive and reliable method of early diagnosis of this fatigue (e.g. heart rate variability – HRV as a modern ob-jective method). The aim of the study was to evaluate whether the HRV monitoring could be a complementary diagnostic tool for overreaching / overtraining in young athletes. Already introduced “classical” indicators of HRV, such as spectral performance and its density in the established frequency ranges, are a part of athlete monitoring in the scope of overreaching prevention We were monitoring the heart rate variability parameters at three different phases of the year-long training cycle and to find out whether in one of these phases we could find athletes showing symptoms of overreaching. Methods: 48 young athletes (33 boys 14.8 ± 1.5 years, 15 girls 14.9 ± 1.7 years) were involved in the study, consisting of 38 boys and 10 girls. There were 15 swimmers (with training volume 9x 1.5‒2 hours a week), 12 artistic gymnasts (with training volume 9x 2‒2.5 hours a week) and 21 badminton players (with training volume 4x weekly 1.5‒2 hours a week). Monitoring was carried out in athletes in three training periods: at the end of the transition period, at the end of the prepared period, at the end of the competition period. Measurements were carried out in the morning. The DiANS PF8 system was used to measure the heart rate variability, the measurements were performed at five-minute intervals: lying-standing-lying. Time and spectral parameters of HRV were monitored. Results: Results of HRV in three periods (HR + rMSSD in lying). Boys: HR (61 ± 8, 64 ± 7, 64 ± 8), rMSSD (85 ± 64; 80 ± 54; 88 ± 59), TS (-0.56 ± 1.53; -0.87 ± 1.4; -0.42 ± 1.44). Girls: HR (65 ± 8; 64 ± 7; 65 ± 8), rMSSD (74 ± 37; 79 ± 35; 83 ± 43), TS (-0.58 ± 1.57; -0.72 ± 1.35); -0.18 ± 0.18). Statistically significant differences (at the significance level = 0.05) among sports were found in Kruskal-Walls ANOVAby Ranks: boys in LF-standing, HF standing, FV, SVB and TS; girls in HF-lying, HF-standing, rMSSD, TP-lying, TP-standing, FV, VA and TS. Conclusion: Monitoring of heart rate variability seems to be a practical tool for prevention of overtraining even in young age. To monitor heart rate variability, we recommend monitoring these parameters: RR, rMSSD, VA, SVB, TS.