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 Poincareplot 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 ms 2 for C, T and OA, respectively) and in upright (640 ± 499, 1814 ± 806 and 1092 ± 712 ms 2 for C, T and OA, respectively; P<0AE05) positions. In supine position, indicators of parasympathetic activity to the sinus node were higher in T compared with C and OA (high-frequency power: 419AE1 ± 381AE2, 1105AE3 ± 781AE4 and 463AE7 ± 715AE 8m s 2 for C, T and OA, respectively; P<0AE05; SD1: 29AE 5±1 8AE5, 75AE 2±1 7AE2 and 37AE 6±2 7AE5 for C, T and OA, respectively; P<0AE05). OA had a marked predominance of sympathetic activity regardless of the position (LF/HF were 0AE47 ± 0AE35, 0AE47 ± 0AE50 and 3AE96 ± 5AE71 in supine position for C, T and OA, respectively, and 2AE09 ± 2AE17, 7AE22 ± 6AE82 and 12AE04 ± 10AE36 in upright position for C, T and OA, respectively). The changes in HRV indexes induced by the upright posture were greater in T than in OA. The shape of the Poincareplots allowed the distinction between the three groups, with wide and narrow shapes in T and OA, respectively, compared with C. As Poincareplot parameters are easy to compute and associated with the 'width' of the scatter gram, they corroborate the traditional time- and frequency-domain analysis. We suggest that they could be used to indicate fatigue and/or prevent OT.