Exercise training augments the dynamic heart rate response to vagal but not sympathetic stimulation in rats

Masaki Mizuno, Toru Kawada, Atsunori Kamiya, Tadayoshi Miyamoto, Shuji Shimizu, Toshiaki Shishido, Scott A. Smith, Masaru Sugimachi

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

We examined the transfer function of autonomic heart rate (HR) control in anesthetized sedentary and exercise-trained (16 wk, treadmill for 1 h, 5 times/wk at 15 m/min and 15-degree grade) rats for comparison to HR variability assessed in the conscious resting state. The transfer function from sympathetic stimulation to HR response was similar between groups (gain, 4.2 ± 1.5 vs. 4.5 ± 1.5 beats·min-1·Hz-1; natural frequency, 0.07 ± 0.01 vs. 0.08 ± 0.01 Hz; damping coefficient, 1.96 ± 0.55 vs. 1.69 ± 0.15; and lag time, 0.7 ± 0.1 vs. 0.6 ± 0.1 s; sedentary vs. exercise trained, respectively, means ± SD). The transfer gain from vagal stimulation to HR response was 6.1 ± 3.0 in the sedentary and 9.7 ± 5.1 beats·min-1·Hz-1 in the exercise-trained group (P = 0.06). The corner frequency (0.11 ± 0.05 vs. 0.17 ± 0.09 Hz) and lag time (0.1 ± 0.1 vs. 0.2 ± 0.1 s) did not differ between groups. When the sympathetic transfer gain was averaged for verylow- frequency and low-frequency bands, no significant group effect was observed. In contrast, when the vagal transfer gain was averaged for very-low-frequency, low-frequency, and high-frequency bands, exercise training produced a significant group effect (P < 0.05 by two-way, repeated-measures ANOVA). These findings suggest that, in the frequency domain, exercise training augments the dynamic HR response to vagal stimulation but not sympathetic stimulation, regardless of the frequency bands.

Original languageEnglish
Pages (from-to)R969-R977
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume300
Issue number4
DOIs
Publication statusPublished - Apr 1 2011
Externally publishedYes

Keywords

  • Heart rate variability
  • Systems analysis
  • Transfer function

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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