The validity of the BioForce Heart Rate Variability System and the use of heart rate variability and recovery to determine the fitness levels of a cohort of university–level rugby players

Abstract

The potential to track changes in training status and fitness levels of especially team sport participants by making use of more time efficient and accessible methods such as heart rate variability (HRV) and heart rate recovery (HRR) cannot be overlooked and needs to be considered. However, studies that have investigated this aspect in team sport participants are scarce. It is against this background that the main objectives of this study were firstly, to determine the relationships between HRV and HRR as well as the fitness levels of a cohort of university-level rugby players. The second objective was to determine the validity of the BioForce Heart Rate Variability System to determine the HRV of a cohort of university-level rugby players. Twenty-four university-level rugby players (age: 20.1 ± 0.41 years; body stature: 182.7 ± 6.2 cm; body mass: 89.7 ± 12.7 kg) of a South African university’s Rugby Institute participated in the first part of the study. During the test day players’ fasting baseline HRV (baseline HRV) values were taken. This was followed by the measurement of the post-breakfast HRV (Pre-Yo-Yo IR1 HRV). Players were then required to perform the Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1) while they were fitted with a portable Cosmed K4b2 gas analyser apparatus and a Fix Polar Heart Rate Transmitter Belt. After completion of the test, HRR was taken on 1 and 3 minutes and followed by the measurement of HRV (Post-Yo-Yo IR1 HRV). For the second part of the study a group of twenty u/21 university-level rugby players (age: 20.06 ± 0.40 years; body stature: 181.8 ± 5.5 cm; body mass: 91.1 ± 10.7 kg) of a South African university’s Rugby Institute were recruited to participate in this study. HRV was measured simultaneously by the Actiheart monitor system as well as the BioForce Heart Rate Variability System over three times periods: during the morning in a fasting state just after players had woken up (baseline); in the morning just after the players ate breakfast (pre-anaerobic); after completion of a high-intensity anaerobic training session (post-anaerobic) and after completion of a 20 min recovery session (post-recovery). Significant correlations (p ≤ 0.05) were found between Pre-Yo-Yo IR1 HRV and heart rate (HR) at the respiratory compensation point (RCP-HR (bpm)) (r = -0.468) as well as oxygen uptake at the RCP (RCP- 2max VO (% of 2max VO )) (r = 0.476), respectively. A forward stepwise regression analysis showed that HR at ventilatory threshold 1 (VT1-HR (bpm)) contributed significantly (p ≤ 0.05) to the post-Yo-Yo IR1 HRV with a variance of 39.8%. Final Yo-Yo IR1 level also contributed significantly (p ≤ 0.05) to 3 minute post-Yo-Yo IR1 HRR with a variance of 16.5%. For the second part of the study the majority of significant relationships (p < 0.05) between the Actiheart and Bioforce obtained HRV results were observed for the post-recovery period (Mean RR, SDNN, RMSSD and Peak LF power), followed by the pre-anaerobic period (Mean R-R and SDNN) and the baseline period (LF:HF ratio). No significant relationships were observed between the HRV results of the two apparatuses during the post-anaerobic period. In conclusion, HRV and HRR may have the potential to act as affordable and easy measurement tools of team sport participants’ fitness levels. However, the study results suggested that the BioForce Heart Rate Variability System that is used to obtain team sport participants’ HRV is especially valid to determine HRV after recovery periods that follow hard training sessions. The results do however cast a shadow of doubt over the accuracy of this apparatus when used directly after hard training sessions.