The aim of the present study was to assess the influence of body posture on post-submaximal exercise parasympathetic reactivation and to examine whether this influence was preserved under a heightened sympathetic background. On four occasions, eleven moderately trained subjects (22.1 +/- 3.0 years old) performed, in random order, two consecutive submaximal running bouts (CTs), each followed by 5 min passive recovery in an upright (Up), sitting (Sit), supine (Sup) or supine with legs up position (SupLu). Between both CTs, participants performed 150 s of supramaximal intermittent running (SI). Parasympathetic reactivation was assessed from heart rate recovery (HRR) and variability (HRV; e.g. rMSSD(30 s)) indices calculated during the 5 min recovery periods [i.e. before (N) and after SI (post-SI)]. In the N condition, Sup position was associated with a faster and greater increase in rMSSD(30 s) than Sit and SupLu (both P < 0.01), which were all higher compared with Up (P < 0.001). A 'time' effect was shown in Sit, Sup and SupLu (all P < 0.05), but not in Up (P = 0.99). All N values were higher than post-SI values (P < 0.001), except for Up, where a trend was apparent (P = 0.06). In the post-SI condition, a position effect was preserved for HRR (P < 0.001), but not for HRV indices (P = 0.99 for rMSSD(30 s)). In conclusion, the supine position accelerated and increased parasympathetic reactivation more than the other three positions, but the posture effect was less evident following supramaximal exercise. In the context of an accentuated sympathetic background (i.e. post-SI), postexercise HRV indices are less gravity dependent than HRR, reflecting more the exercise-related changes in parasympathetic activity.
