Incremental physical exercise led to a significant decrease in the parasympathetic indicator at >50% VO2peak and an increase in the sympathetic indicator at >50-60% VO2peak (P<0.05).
Observational (n=10)
Incremental physical exercise induces a shift in autonomic balance characterized by decreased parasympathetic and increased sympathetic activity, which correlates with changes in heart rate variability.
p-value: p=< 0.05
The objectives of the present study were to investigate autonomic nervous system influence on heart rate during physical exercise and to examine the relationship between the fractal component in heart rate variability (HRV) and the system's response. Ten subjects performed incremental exercise on a cycle ergometer, consisting of a 5-min warm-up period followed by a ramp protocol, with work rate increasing at a rate of 2.0 W/min until exhaustion. During exercise, alveolar gas exchange, plasma norepinephrine (NE) and epinephrine (E) responses, and beat-to-beat HRV were monitored. HRV data were analyzed by "coarse-graining spectral analysis" (Y. Yamamoto and R. L. Hughson. J. Appl. Physiol. 71: 1143-1150, 1991) to break down their total power (Pt) into harmonic and nonharmonic (fractal) components. The harmonic component was further divided into low-frequency (0.0-0.15 Hz) and high-frequency (0.15-0.8 Hz) components, from which low-frequency and high-frequency power (Pl and Ph, respectively) were calculated. Parasympathetic (PNS) and sympathetic (SNS) nervous system activity indicators were evaluated by Ph/Pt and Pl/Ph, respectively. From the fractal component, the fractal dimension (DF) and the spectral exponent (beta) were calculated. The PNS indicator decreased significantly (P 60% VO2peak when there were also more pronounced increases in NE and E.(ABSTRACT TRUNCATED AT 250 WORDS)
Nakamura et al. (Mon,) reported a observational. Incremental physical exercise was evaluated on Parasympathetic (PNS) and sympathetic (SNS) nervous system activity indicators (p=< 0.05). Incremental physical exercise led to a significant decrease in the parasympathetic indicator at >50% VO2peak and an increase in the sympathetic indicator at >50-60% VO2peak (P<0.05).