Can the use of a single integrated unitary autonomic index provide early clues for eventual eligibility for olympic games?

PURPOSE: Optimal autonomic regulation and stress resilience might be considered critical elements of athletic performance. We hypothesize that a novel unitary autonomic index for sports (ANSIs), together with a somatic stress related symptom score (4SQ) might help characterize athletes who were eventually selected for the Rio 2016 Olympic Games Italian team (Rio +). METHODS: In this retrospective study we examined 778 athletes (age 24.4 ± 6.7 yrs) who underwent a planned yearly pre-participation screening. All athletes underwent clinical, autonomic and exercise ECG evaluation. The combination of vagal and sympathetic indices from RR variability into ANSIs was performed by radar plot and percent ranking of index variables. We assessed (Rio +) versus (Rio -) athletes also after subdivision into three sport intensity groups (low, mid and high intensity). RESULTS: Overall there were no significant differences between (Rio +) and (Rio -) athletes when considering individual spectral derived variables. Conversely, the unitary Index ANSIs was significantly higher in (Rio +) compared to (Rio -) athletes (respectively 54.5 ± 29.5 and 47.9 ± 28.4 p = 0.014). This difference was particularly evident (p = 0.017) in the group of athletes characterized by both high static and dynamic components. 4SQ was smaller in the (Rio +) group, particularly in the groups of athletes characterized by both low-medium static and dynamic components. CONCLUSIONS: ANSIs, a proxy of integrated cardiac autonomic regulation and simple assessment of resilience to stress, may differentiate Italian athletes who were eventually selected for participation in the 2016 Rio Olympic Games from those who were not, suggesting the possibility of a "winning functional phenotype".

Heart rate variability to monitor performance in elite athletes: Criticalities and avoidable pitfalls.

BACKGROUND: Spectral analysis of Heart Rate Variability (HRV) is a simple, non-invasive technique that is widely used in sport to assess sympatho-vagal regulation of the heart. Its employment is increasing partly due to the rising usage of wearable devices. However data acquisition using these devices may be suboptimal because they cannot discriminate between sinus and non-sinus beats and do not record any data regarding respiratory frequency. This information is mandatory for a correct clinical interpretation. METHODS: This study involved 974 elite athletes, all of them underwent a complete autonomic assessment, by way of Autoregressive HRV analysis. RESULTS: In 91 subjects (9% of the total population) we observed criticalities of either cardiac rhythm or respiration. Through perusal of one-lead ECG analysis we observed that 77 subjects had atrial or ventricular ectopy, i.e. conditions which impair stationarity and sinus rhythm. Running anyway autonomic nervous system analysis in this population, we observed that RR variance and raw values of LF and HF regions are significantly higher in arrhythmic subjects. In addition 14 subjects had slow (about 6 breath/min, 0.1Hz) respiration. This condition clouds the separation between LF from HF spectral regions of RR interval variability, respectively markers of the prevalent sympathetic and vagal modulation of SA node and of their synergistic interaction. CONCLUSIONS: Caution must be payed when assessing HRV with non-ECG wearable devices. Recording ECG signal and ensuring that respiratory rate is higher than 10 breath/min are both prerequisites for a more reliable analysis of HRV particularly in athletes.

May a unitary autonomic index help assess autonomic cardiac regulation in elite athletes? Preliminary observations on the national Italian Olympic committee team.

BACKGROUND: Long term endurance training, as occurring in elite athletes, is associated to cardiac neural remodeling in favor of cardioprotective vagal mechanisms, resulting in resting bradycardia and augmented contribution of cardiac parasympathetic nerve activity. Autonomic assessment can be performed by way of heart rate variability. This technique however provides multiple indices, and there is not yet complete agreement on their specific significance. Purpose of the study was to assess whether a rank transformation and radar plot could provide a unitary autonomic index, capable to show a correlation between intensity of individual work and quality of autonomic regulation. METHODS: We studied 711 (23.6±6.2 years) elite athletes that took part in the selection procedure for the 2016 Rio Olympic Games for the National Italian Olympic Committee (CONI). Indices from Heart Rate Variability HRV obtained at rest, during standing up and during recovery from an exercise test were used to compute a percent ranked unitary autonomic index for sport (ANSIs), taken as proxy of quality of autonomic regulation. RESULTS: Within the observed wide range of energy expenditure, the unitary autonomic index ANSIs appears significantly correlated to individual and discipline specific training workloads (r=0.25, P<0.001 and r=0.78, P<0.001, respectively), correcting for possible age and gender bias. ANSIs also positively correlates to lipid profile. CONCLUSIONS: Estimated intensity of physical activity correlates with quality of cardiac autonomic regulation, as expressed by a novel unitary index of cardiac autonomic regulation. ANSIs could provide a novel and convenient approach to individual autonomic evaluation in athletes.

Discriminating between two autonomic profiles related to posture in Olympic athletes.

PURPOSE: Autonomic assessment might be useful in training management. We planned to assess whether oscillatory metrics of RR variability (such as LFnu) would be more efficient than static indices from low order statistics (RR variance) at discriminating laying rest from stand posture, as an analog of a shift to sympathetic dominance. METHODS: We studied a large population of elite Olympic athletes: a total of 406 athletes (162 females and 244 males, of similar age 21.7 and 24.4 years) participating to the selection for the upcoming 2016 Olympic games. We employed various methods to extract autonomic indices from RR variability and employed a stepwise statistical approach combining factor and discriminant analysis. RESULTS: We observed that that relative power of oscillatory components from spectral analysis of RR variability (such as LF or HF in nu) and indices from symbolic analysis (particularly 0V) clearly outperform RR variance in discriminating between two physiological conditions (laying rest and stand) related to posture and autonomic activation. CONCLUSIONS: In world class Olympic athletes we have shown that a small subset of RR variability indices, related to sympathovagal balance, may be more appropriate than RR variance to assess excitatory sympathetic autonomic responsiveness of the SA node. These findings may have practical implications for the use of RR variability in guiding training and predicting success in competitions.