Changes in cardiac autonomic regulation after prolonged maximal exercise

Abstract

Harmful cardiac events occurs frequently after exercise. However, the cardiac autonomic regulation after vigorous exercise is not well known. This study was designed to assess heart rate (HR) variability before and after a 75 km cross-country skiing race. HR variability was assessed by using standard statistical measures along with spectral and quantitative Poincarè plot analysis of HR variability in 10 healthy male subjects (age 36 +/- 11 years). The average HR was at the same level 1 day after the race as before the race, but on the second day, HR was significantly lower (P<0.001) compared with the prerace and 1 day after values. The normalized high-frequency (HF) spectral component of HR variability (nuHF) was lower (P<0.01) on the first day after the maximal exercise compared with the pre-exercise values but returned to or even exceeded the prerace level on the second day (P<0.01). The changes in short-term R-R interval variability analysed from the Poincaré plot were similar to those observed in the HF spectral component. The normalized low-frequency (LF) spectral component of HR variability (nuLF) was higher (P<0.01) on the first day after the exercise compared with the prerace levels and it also returned to the pre-exercise level or even dropped below it on the second day after the race. The mean time it took the HF spectral component to return to the pre-exercise level was 4.2 +/- 4.2 h (ranging from 0 to 12 h). This recovery time correlated inversely with the maximal oxygen consumption (VO2max) measured during the bicycle exercise test before the skiing race (r=-0.712, P<0.016). The cardiac vagal outflow is blunted for several hours after prolonged vigorous exercise. The recovery time of reduced vagal outflow depends on individual cardiorespiratory fitness and there is an accentuated rebound of altered autonomic regulation on the second day after prolonged exercise.

Heart rate variability is related to training load variables in interval running exercises

“…Hynynen et al (2010) studied the effects of single moderate and heavy (marathon) endurance exercise sessions on nocturnal HRV, and found that both sessions affected nocturnal HR and HRV, HFP being only 77 % and 34 % of the nocturnal values of a resting day after moderate and heavy exercises, respectively. Hautala et al (2001) also reported decreased HRV during the night fol-lowing a 75 km cross-country ski-race, followed by a rebound phenomenon during the second night after the race. They also reported large interindividual variation in the recovery time of HFP to the pre-race level after the ski-race (0-14 h, mean 8.2 h).…”

“…It has been found in previous studies (Hautala et al 2001;Hynynen et al 2010;Mourot et al 2004) that the recovery of vagal modulation may be delayed even 24-48 h after a prolonged high-intensity exercise. In the present study, no differences were found in the nocturnal HR or HRV between the nights before and after the experimental exercises.…”

“…They studied the effects of high-intensity sprint exercises on immediate 10 min HRV recovery of trained athletes, and found highly impaired vagal reactivation during the first minutes of recovery. According to previous studies (Hautala et al 2001;Javorka et al 2002;Oida et al 1997;Seiler et al 2007;Takahashi et al 2000), HRV increases slowly towards resting values during recovery after single exercise session, but the effects of endurance exercise may last from minutes (Gladwell et al 2010;Seiler et al 2007) to even 48 hours (Mourot et al 2004), depending on physical TL, i.e. the combined effect of exercise intensity and duration, of the exercise as well as the training status of the subjects.…”

“…They also reported large interindividual variation in the recovery time of HFP to the pre-race level after the ski-race (0-14 h, mean 8.2 h). According to the results of Hautala et al (2001), subjects with better cardiorespiratory fitness had a more rapid recovery.…”

“…In previous studies, it has been shown that the effects of a high-intensity prolonged exercise on post-exercise HRV may be observed until the night following exercise or even longer (Hautala et al 2001;Hynynen et al 2010;Mourot et al 2004), either when compared to resting day (Hautala et al 2001) or some kind of control exercise Myllymäki et al 2012). In the study of Hynynen et al (2010), the intensity of the baseline exercise was increased, so the exact effects of the increased duration of exercise cannot be analyzed, but the results of the study indicated a long-lasting decrement of vagal activation after high-intensity endurance exercise.…”