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Equine veterinary journal2000; 32(3); 253-262; doi: 10.2746/042516400776563572

Frequency domain analysis of heart rate variability in horses at rest and during exercise.

Abstract: The pattern of variation in heart rate on a beat-to-beat basis contains information concerning sympathetic (SNS) and parasympathetic (PNS) contributions to autonomic nervous system (ANS) modulation of heart rate (HR). In the present study, heart period (RR interval) time series data were collected at rest and during 3 different treadmill exercise protocols from 6 Thoroughbred horses. Frequency and spectral power were determined in 3 frequency bands: very low (VLF) 0-0.01-0.07-< or = 0.5 cycles/beat. Indicators of sympathetic (SNSI = LO/HI) and parasympathetic (PNSI = HI/TOTAL) activity were calculated. Power in all bands fell progressively with increasing exercise intensity from rest to trot. At the gallop VLF and LO power continued to fall but HI power rose. SNSI rose from rest to walk, then fell with increasing effort and was lowest at the gallop. PNSI fell from rest to walk, then rose and was highest at the gallop. Normalised HI power exceeded combined VLF and LO power at all gaits, with the ratio HI to LO power being lowest at the walk and highest at the gallop. ANS indicators showed considerable inter-horse variation, and varied less consistently than raw power with increasing physical effort. In the horses studied, the relationship between power and HR changed at exercise intensities associated with heart rates above approximately 120-130 beats/min. At this level, humoral and other non-neural mechanisms may become more important than autonomic modulation in influencing heart rate and heart rate variability (HRV). HRV at intense effort may be influenced by respiratory-gait entrainment, energetics of locomotion and work of breathing. HRV analysis in the frequency domain would appear to be of potential value as a noninvasive means of assessing autonomic modulation of heart rate at low exercise intensities, only. The technique may be a sensitive method for assessing exercise response to experimental manipulations and disease states.
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Publication Date: 2000-06-03 PubMed ID: 10836482DOI: 10.2746/042516400776563572Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This study investigated the variability in heart rate in horses both at rest and during various levels of exercise. The researchers gathered data about the frequency and spectral power of heartbeats within various frequency ranges, and analyzed how these changed in relation to exercise intensity. The findings indicate that heart rate variability may be influenced by factors other than autonomic nervous system activity during intense exercise.

Methodology

  • Data for this study were gathered by monitoring the heart rates of six Thoroughbred horses at rest and during three different treadmill exercise protocols.
  • The researchers tracked the timings of individual heartbeats (RR intervals) to create time series data for analysis.
  • The frequencies of the heartbeats were categorized into three bands: very low (VLF), low (LO), and high (HI). These bands represent different levels of physical stress on the heart.
  • The study also calculated indicators of both sympathetic (SNSI) and parasympathetic (PNSI) nerve activity. These provide an understanding of how the autonomic nervous system (ANS) regulates heart rate.

Results

  • The power in all frequency bands fell progressively with an increase in exercise intensity. This trend continued up to a trotting pace, but at a galloping pace, the power in the high frequency (HI) band increased.
  • The sympathetic activity indicator (SNSI) increased from rest to walking pace, but fell with further increases in physical exertion, reaching its lowest at a galloping pace.
  • The parasympathetic activity indicator (PNSI), meanwhile, fell from rest to a walking pace, then rose with increased physical exertion, peaking at a galloping pace.
  • Results showed significant variation between individual horses, suggesting inter-horse variability in heart rate responses.

Conclusion

  • You could conclude from the study that heart rate and heartbeat variability in horses changed in response to increasing levels of physical effort in ways that indicate both neural and non-neural influences acting on heart rate.
  • There is a change in autonomic modulation once heart rate reaches high exercise intensities above 120-130 beats per minute.
  • Variables such as respiratory-gait entrainment, energetics of locomotion and work of breathing could also have influenced heart rate variability during intense exercise.
  • The study suggests that frequency domain analysis of heart rate variability could be a non-invasive means of assessing autonomic modulation of heart rate at low exercise intensities.

Cite This Article

APA
Physick-Sheard PW, Marlin DJ, Thornhill R, Schroter RC. (2000). Frequency domain analysis of heart rate variability in horses at rest and during exercise. Equine Vet J, 32(3), 253-262. https://doi.org/10.2746/042516400776563572

Publication

Equine veterinary journal
ISSN: 0425-1644
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 32
Issue: 3
Pages: 253-262

Researcher Affiliations

Physick-Sheard, P W
  • Department of Population Medicine and Clinical Studies, Ontario Veterinary College, University of Guelph, Canada.
Marlin, D J
    Thornhill, R
      Schroter, R C

        MeSH Terms

        • Algorithms
        • Animals
        • Autonomic Nervous System / physiology
        • Blood Gas Analysis / veterinary
        • Blood Pressure
        • Electrocardiography / veterinary
        • Fourier Analysis
        • Gait / physiology
        • Heart Rate / physiology
        • Horses / physiology
        • Mass Spectrometry / veterinary
        • Physical Conditioning, Animal / physiology
        • Random Allocation
        • Rest / physiology
        • Time Factors

        Citations

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