Effects of initial handling and training on autonomic nervous function in young Thoroughbreds.
OBJECTIVE
To determine the effects of initial handling and training on autonomic nervous functions in young Thoroughbreds.


METHODS
63 healthy Thoroughbreds.


METHODS
All horses were trained to be handled and initially ridden in September of the yearling year and then trained until the following April by conventional training regimens. To obtain the heart rate (HR), electrocardiograms were recorded in the stable before initial handling and training and following 7 months of training; variations in HR were then evaluated from the power spectrum in terms of the low frequency (LF; 0.01 to 0.07 Hz) power and high frequency (HF; 0.07 to 0.6 Hz) power as indices of autonomic nervous activity. To evaluate the fitness, the V200 (velocity at HR of 200 beat/min), which is reflective of the aerobic capacity of the horse, was measured.


RESULTS
Mean (+/- SE) resting HR decreased significantly from 41.5 +/- 0.8 to 38.7 +/- 0.4 beat/min following 7 months of training. The LF power of horses increased significantly from 1,037 +/- 128 milliseconds2 in September of the yearling year to 2,944 +/- 223 milliseconds2 in the following April. Similarly, the HF power increased significantly from 326 +/- 30 milliseconds2 to 576 +/- 39 milliseconds2 at the corresponding time points. The V200 increased significantly following training.


CONCLUSIONS
Increases in LF and HF powers indicate that parasympathetic nervous activity increases in horses by 7 months of training. The decrease in resting HR may be dependent on the training-induced increase of parasympathetic nervous activity in Thoroughbreds.
Ohmura
Hajime
H
Equine Science Division, Hidaka Training and Research Center, Japan Racing Association, Hokkaido.
Hiraga
Atsushi
A
Aida
Hiroko
H
Kuwahara
Masayoshi
M
Tsubone
Hirokazu
H
D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D015716:Electrocardiography, Ambulatory / Q000662:veterinary; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006736:Horses / Q000502:physiology*; D008297:Male; D010805:Physical Conditioning, Animal / Q000502:physiology*