Decrease in heart rate variability with overtraining: assessment by the Poincaré plot analysis

Summary Numerous symptoms have been associated with the overtraining syndrome (OT), including changes in autonomic function. Heart rate variability (HRV) provides non‐invasive data about the autonomic regulation of heart rate in real‐life conditions. The aims of the study were to: (i) characterize the HRV profile of seven athletes (OA) diagnosed as suffering of OT, compared with eight healthy sedentary (C) and eight trained (T) subjects during supine rest and 60° upright, and (ii) compare the traditional time‐ and frequency‐domain analysis assessment of HRV with the non‐linear Poincaré plot analysis. In the latter each R‐R interval is plotted as a function of the previous one, and the standard deviations of the instantaneous (SD1) and long‐term R‐R interval variability are calculated. Total power was higher in T than in C and OA both in supine (1158 ± 1137, 6092 ± 3554 and 2970 ± 2947 ms2 for C, T and OA, respectively) and in upright (640 ± 499, 1814 ± 806 and 1092 ± 712 ms2 for C, T and OA, respectively; P