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Effects of initial handling and training on autonomic nervous function in young Thoroughbreds

Hajime OhmuraEquine Science Division, Hidaka Training and Research Center, Japan Racing Association, 535-13 Aza-Nishicha, Urakawacho, Urakawa-gun, Hokkaido 057-0171 Japan.

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Atsushi HiragaEquine Science Division, Hidaka Training and Research Center, Japan Racing Association, 535-13 Aza-Nishicha, Urakawacho, Urakawa-gun, Hokkaido 057-0171 Japan.

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Hiroko AidaEquine Science Division, Hidaka Training and Research Center, Japan Racing Association, 535-13 Aza-Nishicha, Urakawacho, Urakawa-gun, Hokkaido 057-0171 Japan.

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Masayoshi KuwaharaDepartment of Comparative Pathophysiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657 Japan.

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Hirokazu TsuboneDepartment of Comparative Pathophysiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657 Japan.

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Abstract

Objective—To determine the effects of initial handling and training on autonomic nervous functions in young Thoroughbreds.

Animals—63 healthy Thoroughbreds.

Procedure—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 and Clinical Relevance—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. (Am J Vet Res 2002;63:1488–1491)

Abstract

Objective—To determine the effects of initial handling and training on autonomic nervous functions in young Thoroughbreds.

Animals—63 healthy Thoroughbreds.

Procedure—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 and Clinical Relevance—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. (Am J Vet Res 2002;63:1488–1491)