The effect of weekly training and a game on heart rate variability in elite youth Rugby League players

Introduction: To date, the majority of research related to rugby league has investigated movement patterns, injury mechanisms and the effects of training workload and a game on player fatigue. Interest in monitoring player workloads and recovery has increased recently, with heart rate variability (HRV) proposed as an important monitoring tool in both individual and team sports [1, 2]. Due to the high physical demands associated with rugby league, monitoring alterations in cardiac autonomic control via HRV may lead to improved player management and enhanced performance. The aim of this study was to investigate the influence of weekly training and a competitive game on HRV in elite youth rugby league players, and to identify the importance of HRV as a monitoring tool for Rugby League player preparation.\ud \ud Methods: Youth rugby league players (n=9) were monitored during supine rest (10 min) at 2 days prior to a game (Pre-2), day of the game (Game Day), and 1 (Post-1), 2 (Post-2) and 4 (Post-4) days following a game. Heart rate (HR) recordings were recorded via a chest strap transmitter with beat-by-beat intervals during the last 5 min of supine rest analysed for time domain, frequency domain (low frequency [LF], high frequency [HF]) and non-linear measures of HRV. Player daily training load was calculated from players’ rating of perceived exertion and session duration as previously described (Foster, 1998). Significant (p<0.05) differences in HRV over the monitoring days were identified via 1-way ANOVA and post-hoc pairwise comparisons with a Bonferroni correction or a Friedman’s test with a Conover post-hoc comparison, where appropriate. Relationships between HRV variables and training loads were identified using Spearman’s rank rho (ρ) correlation coefficients.\ud \ud Results: All time domain and nonlinear measures of HRV were similar over the 5 monitoring days except for mean HR, which was significantly greater on Game Day and Post-1 compared to Pre-2 (73.0 ± 5.7 and 80.1 ± 8.1 vs. 64.9 ± 8.7 beats per minute). On Game Day, LF and the ratio between LF and HF were significantly increased and remained elevated until Post-2 (Figure 1). In contrast, HF was significantly reduced on Game day and remained low until Post-2 (Figure 1). A strong negative correlation was identified between mean HR and training load on Pre-2 (ρ = -0.783, p < 0.05) with a strong positive correlation identified between HF and training load on Pre-2 (ρ = 0.700, p < 0.05).\ud \ud Conclusion/Discussion: Prior to a competitive game, elite youth, Rugby League players exhibited a significant reduction in HRV that was sustained for at least 24 hours post-game. This withdrawal of parasympathetic and/or increased sympathetic control of HR possibly may result from pre-match anxiety as well as the physical demands of the game. Strong relationships between HRV and training load at Pre-2 indicate that early monitoring may assist in identifying training workloads for the upcoming week. The current results support HRV as an important monitoring tool for managing training workload