Changes in heart rate variability in horses during immersion in warm springwater

Tomohiro Kato DVM1, Hajime Ohmura DVM, PhD2, Atsushi Hiraga DVM, PhD3, Shinya Wada DVM4, Masayoshi Kuwahara PhD5, and Hirokazu Tsubone DVM, PhD6
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  • 1 Joban Branch, Equine Research Institute, Japan Racing Association, 71 Uenohara, Joban shiratori-machi, Iwaki-shi, Fukushima 972-8325 Japan.
  • | 2 Equine Science Division, Hidaka Training and Research Center, Japan Racing Association, 535-13 Aza-Nishicha, Urakawa-cho, Urakawa-gun, Hokkaido 057-0171 Japan.
  • | 3 Equine Science Division, Hidaka Training and Research Center, Japan Racing Association, 535-13 Aza-Nishicha, Urakawa-cho, Urakawa-gun, Hokkaido 057-0171 Japan.
  • | 4 Joban Branch, Equine Research Institute, Japan Racing Association, 71 Uenohara, Joban shiratori-machi, Iwaki-shi, Fukushima 972-8325 Japan.
  • | 5 Department of Comparative Pathophysiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyoku, Tokyo 113-8657 Japan.
  • | 6 Department of Comparative Pathophysiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyoku, Tokyo 113-8657 Japan.

Abstract

Objective—To determine the effects of immersion in warm springwater (38° to 40°C) on autonomic nervous activity in horses.

Animals—10 male Thoroughbreds.

Procedure—Electrocardiograms were recorded from horses for 15 minutes during a warm springwater bath after being recorded for 15 minutes during stall rest. Variations in heart rate (HR) were evaluated from the power spectrum in terms of 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.

Results—Mean (±SE) HR during stall rest and immersion in warm springwater was 31.1 ± 1.7 and 30.3 ± 1.0 beat/min, respectively. No significant difference was found between the HR recorded during stall rest and that recorded during immersion in warm springwater. The HF power significantly increased from 1,361 ± 466 milliseconds2 during stall rest to 2,344 ± 720 milliseconds2 during immersion in warm springwater. The LF power during stall rest and immersion in warm springwater was 3,847 ± 663 and 5,120 ± 1,094 milliseconds2, respectively, and were not significantly different from each other. Similarly, the LF:HF ratio did not change during immersion in warm springwater. The frequency of second-degree atrioventricular block, which was observed in 2 horses, increased during immersion in warm springwater, compared with during stall rest.

Conclusions and Clinical Relevance—Increases in HF power indicates that the parasympathetic nervous activity in horses increases during immersion in warm springwater. Thus, immersion in warm springwater may provide a means of relaxation for horses. ( Am J Vet Res 2003;64:1482–1485)

Abstract

Objective—To determine the effects of immersion in warm springwater (38° to 40°C) on autonomic nervous activity in horses.

Animals—10 male Thoroughbreds.

Procedure—Electrocardiograms were recorded from horses for 15 minutes during a warm springwater bath after being recorded for 15 minutes during stall rest. Variations in heart rate (HR) were evaluated from the power spectrum in terms of 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.

Results—Mean (±SE) HR during stall rest and immersion in warm springwater was 31.1 ± 1.7 and 30.3 ± 1.0 beat/min, respectively. No significant difference was found between the HR recorded during stall rest and that recorded during immersion in warm springwater. The HF power significantly increased from 1,361 ± 466 milliseconds2 during stall rest to 2,344 ± 720 milliseconds2 during immersion in warm springwater. The LF power during stall rest and immersion in warm springwater was 3,847 ± 663 and 5,120 ± 1,094 milliseconds2, respectively, and were not significantly different from each other. Similarly, the LF:HF ratio did not change during immersion in warm springwater. The frequency of second-degree atrioventricular block, which was observed in 2 horses, increased during immersion in warm springwater, compared with during stall rest.

Conclusions and Clinical Relevance—Increases in HF power indicates that the parasympathetic nervous activity in horses increases during immersion in warm springwater. Thus, immersion in warm springwater may provide a means of relaxation for horses. ( Am J Vet Res 2003;64:1482–1485)