Effects of Exercise Training on Left Ventricular Hypertrophy and Cardiac Regulation in Elite Athletes: Insight from a Composite Index Proxy of Autonomic Control

The “athlete’s heart” represents a physiological condition consequent to long-term adaptation to sport-specific training loads. Cardiac imaging is a pivotal tool in the assessment of athletes. The study of the autonomic nervous system (ANS) using heart rate variability is becoming increasingly popular in sports fields, given its fundamental role in cardiovascular adaptation to exercise. Unfortunately, many barriers limit the clinical use of this methodology. In this observational study of 330 elite athletes, we used a composite index of ANS control (ANSI), designed to overcome pitfalls, following the hypothesis that studying the ANS could help address cardiac adaptation to high-volume training. In athletes subdivided into three groups considering the level (LOW/HIGH) of combined static/dynamic exercise and the presence [+]/absence [−] of left ventricular hypertrophy (LVH), we found that ANSI showed a progressive increase (LOW: 38.2 ± 27.6%; HIGH-LVH [−]: 52.1 ± 27.2%; HIGH-LVH [+]: 64.4 ± 24.9%, J-T test p < 0.001), with significant differences between all groups considered (p < 0.001). After adjustment and within the HIGH group, ANSI showed the strongest association with LVH and the highest explanatory power among autonomic variables. In conclusion, ANSI was able to differentiate elite athletes characterized by different cardiac remodeling and workloads (as suggested by different sport disciplines), corroborating the hypothesis for a wider use of ANS evaluation in the sports field.