Heart rate variability before and after cycle exercise in relation to different body positions

Abstract

The purpose of this study was to assess the effect of three different body positions on HRV measures following short-term submaximal exercise. Thirty young healthy males performed submaximal cycling for five minutes on three different occasions. Measures of HRV were obtained from 5-min R to R wave intervals before the exercise (baseline) and during the last five minutes of a 15 min recovery (post-exercise) in three different body positions (seated, supine, supine with elevated legs). Measures of the mean RR normal-to-normal intervals (RRNN), the standard deviation of normal-to-normal intervals (SDNN), the root mean square of successive differences (RMSSD) and the low-frequency (LF) and the high-frequency (HF) spectral power were analyzed. Post-exercise RRNN, RMSSD were significantly higher in the two supine positions (p < 0. 01) compared with seated body position. Post-exercise ln LF was significantly lower in the supine position with elevated legs than in the seated body position (p < 0.05). No significant difference was found among the three different body positions for post-exercise ln HF (p > 0.05). Post-exercise time domain measures of HRV (RRNN, SDNN, RMSSD) were significantly lower compared with baseline values (p < 0.01) regardless body position. Post-exercise ln LF and ln HF in all three positions remained significantly reduced during recovery compared to baseline values (p < 0.01). The present study suggests that 15 minutes following short-term submaximal exercise most of the time and frequency domain HRV measures have not returned to pre-exercise values. Modifications in autonomic cardiac regulation induced by body posture present at rest remained after exercise, but the post-exercise differences among the three positions did not resemble the ones established at rest. Key pointsWhether different body positions may enhance post-exercise recovery of autonomic regulation remains unclear.The absence of restoration of HRV measures after 15 minutes of recovery favor the existence of modifying effects of exercise on mechanisms underlying heart regulation.On the basis of discrepancies in HRV measures in different body positions pre- and post-exercise we argue that the pace of recovery of cardiac autonomic regulation is dependent on body posture.

Keywords: Heart rate variability; exercise; recovery.

Figure 1.

Schematic desription of experimental design. After rest-phase participants underwent a submaximal cycling followed by recovery-phase. Heart rate variability was registered 5 minutes at rest (baseline) and during the last 5 minutes of a 15 minute recovery (post-exercise). Baseline and post-exercise measurements were carried out in different body positions (seated upright on cycle ergometer-protocol I, supine-protocol II, and supine with elevated legs-protocol III).

Figure 2.

Relative changes of time and frequency domain HRV parameters pre- and post-exercise. RRNN, mean RR normal-to-normal interval; SDNN, standard deviation of normal-to-normal intervals; RMSSD, root mean square of succes-sive differences; ln LF, natural logarithm of low-frequency spectral power; ln HF, natural logarithm of high-frequency spectral power.