title: Influence of training on autonomic nervous function in horses: evaluation by power spectral analysis of heart rate variability.
abstract: We studied the influence of training on autonomic nervous function in the horse. For this purpose, Holter electrocardiogram (ECG) was recorded before and after training from 24 Thoroughbred horses (2-year-olds) and autonomic nervous function was evaluated by the power spectral analysis of heart rate (HR) variability. We obtained HR, low-frequency (LF) power, high-frequency (HF) power, and LF/HF ratio from recording. We set LF at 0.01-0.07 Hz and HF at 0.07-0.6 Hz. The HF power is thought to reflect primarily parasympathetic nervous function. Both the sympathetic and parasympathetic nervous systems have been shown to contribute to the LF power. The LF/HF ratio is considered as an index of the cardiac sympathovagal balance. Second degree atrioventricular blocks were found in the ECG of 3 and 5 horses before and after the training period, respectively. Ventricular premature depolarisations were detected in a horse after the training period. Heart rate decreased at night. The lowest HR values had a tendency to appear in the early morning. Both the LF and HF power tended to be higher at night. However, the LF/HF ratio was almost the same throughout the day. The HR was significantly decreased by training. Although the LF power and LF/HF ratio were significantly increased, the HF power was not changed by training. These results suggest that parasympathetic nervous activity may be fully activated even before training in this species.
authors.affiliation: Department of Comparative Pathophysiology, Graduate School of Agriculture and Life Sciences, University of Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kuwahara
authors.forename: A
authors.initials: A
authors.lastname: Hiraga
authors.forename: M
authors.initials: M
authors.lastname: Kai
authors.forename: H
authors.initials: H
authors.lastname: Tsubone
authors.forename: S
authors.initials: S
authors.lastname: Sugano
mesh_terms: D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D002940:Circadian Rhythm; D004562:Electrocardiography / Q000379:methods / Q000662:veterinary*; D006339:Heart Rate / Q000502:physiology*; D006736:Horses / Q000502:physiology*; D010805:Physical Conditioning, Animal / Q000502:physiology*