Heart Rate Variability And Autonomic Activity In A Nonfunctional Overreached Professional Soccer Player

Abstract

PURPOSE: In order to investigate nonfunctional overreaching (NFOR) related adaptations in the autonomic nervous system, heart rate variability (HRV) was examined in a professional soccer player (age: 28.6 years; weight: 77.4 kg; height: 177.1 cm; adiposity: 12.1 %; VO2 Max 57 ml/kg/min) who showed reduced performance in competitions, frequent muscular fatigue during some training sessions (same period), and finally getting upper respiratory tract infection (URTI). METHODS: HRV analysis was performed once a week during three periods of competitive season: initial, NFOR state and post-recovery (5-month follow-up). Short-term recordings (5 minutes) were made with a Polar RS800CX heart rate monitor in two positions: supine (S) and 90° head-up tilt (T), immediately after awakening (match day morning). Root mean square of successive differences (RMSSD) and power spectral density were measured. LF/HF ratios in S and T positions were calculated and mean resting heart rate (RHR) was also analyzed. Seven players from the same team and with normal performances during the season were used as a control group (age: 26.6 ± 3.1 years; weight: 73.2 ± 6 kg; height: 176.7 ± 10 cm; adiposity: 12.9 ± 1.6 %; VO2 Max 55.7 ± 1.8 ml/kg/min). The typical 95% confidence interval (CI) in every HRV parameter was calculated in this group. To be diagnosed as NFOR, the subject (case) had to reveal a 95% difference with respect to the lower or upper CI limit reported in the control group. Values are expressed as mean ± SD. RESULTS: LF/HF ratio decreased progressively throughout the competitive period in S and it was substantially different in comparison with control subjects in T during the NFOR state (0.26 ± 0.62 vs. 2.03 ± 1.25). Relevant differences of RMSSD in S (107.6 ± 20.2 vs. 74.6 ± 23.8 ms) and T (140.3 ± 15.3 vs. 61.6 ± 21.6 ms) were found in NFOR. According to this phenomenon, RHR was lower than the control group in S (45.3 ± 1.7 vs. 55.7 ± 6.5 bpm) and T (48.2 ± 2.4 vs. 59.8 ± 9.1 bpm) and returned to baseline after recovery. CONCLUSIONS: The results suggest a sympathovagal imbalance with extensive parasympathetic modulation in a player identified as overreached. Relevant increase of RMSSD and decrease of LF/HF ratio reflect alterations in autonomic function, which should be taken into account when complete recovery is essential to prevent overtraining syndrome.