Resumen de Autonomic Recovery after Exercise in Trained Athletes: Intensity and Duration Effects

Stephen K. Seiler, Olav Haugen, Erin Kuffel

• Purpose: To investigate the effects of training intensity and duration, through a range representative of training in endurance athletes, on acute recovery of autonomic nervous system (ANS) balance after exercise.

  Methods: Nine highly trained (HT) male runners (V?O2max 72 ± 5 mL·kg·min-1, 14 ± 3 training hours per week) and eight trained (T) male subjects (V?O2max 60 ± 5 mL·kg·min-1, 7 ± 1 training hours per week) completed preliminary testing to determine ventilatory thresholds (VT1, VT2) and V?O2max. HT performed four intensity-controlled training sessions: 60 min and 120 min below VT1; 60 min with 30 min between VT1 and VT2 (threshold); and 60 min above VT2 (6 × 3 min at 96% V?O2max, 2 min of recovery). T also completed the interval session to compare ANS recovery between HT and T. Supine heart rate variability (HRV) was quantified at regular intervals through 4 h of recovery.

  Results: When HT ran 60 or 120 min below VT1, HRV returned to pretraining values within 5-10 min. However, training at threshold (2.7 ± 0.4 mM) or above VT2 (7.1 ± 0.7 mM) induced a significant, but essentially identical, delay of HRV recovery (return to baseline by approximately 30 min). In T, HRV recovery was significantly slower, with HRV returning to baseline by =90 min after the same interval session.

  Conclusions: In the highly trained endurance athlete, exercise for =120 min below the first ventilatory threshold causes minimal disturbance in ANS balance. ANS recovery is more rapid in highly trained than in trained subjects after high-intensity exercise. Further, the first ventilatory threshold may demarcate a "binary" threshold for ANS/HRV recovery in highly trained athletes, because further delays in HRV recovery with even higher training intensities were not observed.