Cardiac autonomic disturbance following sprint-interval exercise in untrained young males: Does exercise volume matter?

Abstract

Objectives: This study examined the influences of the volume of all-out sprint-interval exercise (SIE) on acute post-exercise heart rate variability (HRV) recovery.

Methods: HRV recovery following a session of (i) 2 × 30-s SIE (SIE₂), (ii) 4 × 30-s SIE (SIE₄), and (iii) non-exercising control (CON) were compared in 15 untrained young males. Time domain [standard deviation of normal-to-normal intervals, root mean square of successive R-R differences] and frequency domain [low frequency (0.04-0.14 Hz), high frequency (0.15-0.40 Hz)] measures of HRV were assessed every 20 min for 140 min after the exercise, and every hour during the first 4 h of actual sleep time at immediate night. All trials were scheduled at 19:00.

Results: In comparison to CON, both SIE₂ and SIE₄ attenuated the HRV markedly (p < 0.05), while the declined HRV restored progressively during recovery. Although the sprint repetitions of SIE₄ was twice as that of SIE₂, the declined HRV indices at corresponding time points during recovery were not different between the two trials (p > 0.05). Nevertheless, the post-exercise HRV restoration in SIE₂ appeared to be faster than that in SIE₄. Regardless, nocturnal HRV measured within 10 h following the exercise was not different among the SIE and CON trials (p > 0.05).

Conclusion: Such findings suggest that the exercise volume of the SIE protocol may be a factor affecting the rate of removal of the cardiac autonomic disturbance following the exercise. In addition, rest for ∼10 h following either session of the SIE protocol appears to be appropriate for the cardiovascular system to recover.

Keywords: Cardiac health; Cardiac parasympathetic activity; Cardiovascular system; Heart rate variability; Sprint-interval training.

Fig. 1

The time courses of (a) heart rate, (b) log standard deviation of normal to normal intervals (LnSDNN), and (c) log root mean square of successive R-R differences (LnRMSSD) before (Pre) and after the exercise, and during the first 4 h of actual sleep time in CON, SIE₂, and SIE₄ trials. Trial abbreviations refer to the text. ∗ significant different from corresponding CON value; ^a significant different from corresponding pre-exercise value.

Fig. 2

The time courses of (a) log low frequency (LnLF), (b) log high frequency (LnHF), and (c) LF/HF ratio before (Pre) and after the exercise, and during the first 4 h of actual sleep time in CON, SIE₂, and SIE₄ trials. Trial abbreviations refer to the text. The expressions of symbols for statistical significance refer to Fig. 1.

Fig. 3

The time courses of systolic and diastolic blood pressure before (Pre) and after the exercise, and during the first 4 h of actual sleep time in CON, SIE₂, and SIE₄ trials. Trial abbreviations refer to the text. The expressions of symbols for statistical significance refer to Fig. 1.