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

The research explores the effects of horses being immersed in warm spring water on their autonomic nervous activity. It found that warm spring water baths might increase parasympathetic nervous activity in horses, potentially providing a means of relaxation.

Research Methodology

The researchers used 10 male Thoroughbreds for their study. Their autonomic nervous activity was monitored in two different settings:

• During 15 minutes of stall rest – this served as the baseline or control reading.
• Subsequently during 15 minutes of immersion in warm springwater which was maintained between 38 to 40 degree Celsius.

The tool used to measure autonomic nervous activity was an electrocardiogram (ECG), which records the heart’s rhythm and electrical activity. From these ECGs, the researchers evaluated variations in heart rate based on the power spectrum in terms of low frequency and high-frequency power. These frequencies act as indices of the autonomic nervous activity.

Results

While the study did not find any significant difference in the heart rates recorded during stall rest and warm springwater immersion, it did observe other noteworthy changes:

• The high-frequency (HF) power significantly increased from 1,361 milliseconds squared during stall rest to 2,344 milliseconds squared during immersion in warm springwater. The increase in HF power implies increased parasympathetic nervous activity.
• The low-frequency (LF) power and the LF:HF ratio were not significantly different in both situations.
• There was an increase in the frequency of second-degree atrioventricular block in 2 horses during immersion compared to stall rest. This condition is a type of heart block in which the electrical signals between the chambers of the heart are partially blocked.

Conclusions

This research provides evidence that immersion in warm springwater could potentially increase the parasympathetic nervous activity in horses. This increase signifies a state of relaxation, suggesting that warm springwater baths could be a method of relaxing horses, though further research may be necessary to confirm these findings and understand the extent of implications, particularly regarding the instances of the second-degree atrioventricular block.