Heart Rate Variability and psychophysiological evaluation of competitive athletes engaged in dynamic pistol shooting tournaments

Action shooting competitions (ACS) of the International Pistol Shooting Confederation are a worldwide sports activity consisting in stages needing awareness, quick decision-making and tactics to manage simultaneous bursts of psychological and physical stress. Cardiovascular load can be unexpectedly higher and cardiac autonomic response (CAR) different if compared to academic shooting. High anxiety and low management of emotions can reduce the performance and the ability to be accurate in such complex shooting task. Aim: To evaluate CAR during shooting simulator training (SST) and during ASC. To correlate individual performance score with the level of anxiety and with Heart Rate Variability (HRV) parameters. Methods: 3-lead ECG of 30 athletes was continuously monitored before, during and after training at SST with programmable degrees of skill requirements and during ASC. Anxiety was assessed with the State-Trait Anxiety Inventory-Trait (STAI), before and after shooting tasks. HRV parameters were computed from short-term (120-seconds) intervals, in the time-domain (TD), frequency-domain (FD) and with non-linear (NL) methods [Poincarè plot (PP), Recurrence plot (RP), Detrended fluctuation analysis (DF), Approximate entropy (AE), Sample entropy (SE), Correlation dimension (CD)]. Time-varying spectral analysis was used to visualize transient fluctuations (Figure 1A) of FD components. LF/HF ratio was accepted as an index of different CAR induce by SST and ASC (Figure 1B). Discriminant Analysis (DA) was applied to HRV parameters to differentiate SST- and ASC- induced stress (Figure 1C). Results: All athletes were in good psychological balance, with no evidence of individual tendency to respond with abnormal levels of state anxiety to the test challenges. Sympatho-vagal modulation was different during SST and ASC (Figure 1B). At univariate analysis, most NL parameters, SDNN/RMSSD and LF/HF ratio were significantly different (p<0.05) between SST and ASC. By combining short-term TD HRVtri, and NL PPsd1/sd2, RPrec and DFalfa1 in the formulas: [F1= 9.68 x sd1/sd2 - 0.2 x HRVtri + 0.12 x RPrec – 1.6 x DFalfa1 - 4.82] and [F2= 10.7 x sd1/sd2 + 0.48 x HRVtri + 0.04 x RPrec + 1.56 x DFalfa1 – 10.1], DA differentiated rest from stress induced by SST and by ASC with 91.8% predictive accuracy (PA). The two stress conditions were separated with 97% PA, with F1= 8.9 x sd1/sd2 - 0.2 x HRVtri + 0.1 x RPrec – 1.03 x DFalfa1 – 5.8 (ASC if F1 > 1). Higher task-related anxiety was correlated with lower shooting accuracy during both TTS and ASC. Conclusions: DA of HRV parameters is efficient in differentiating stress induced by SST and ASC. ASC is unrivalled to test individual capability to manage strong emotional reactions in competition. SST, although less demanding, provides objective correlation between tasks difficulty and performance, allows precise storage of scores and is helpful to design individualized training methods for the competitive shooter.