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Cardiac cycle length variability in ponies at rest and during exercise
K S Rugh1, B Jiang, D Hatfield
1John M. Dalton Research Center, University of Missouri-Columbia 65211.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|October 1, 1992
Summary
Cardiac cycle length variability in ponies significantly decreases with exercise. Atropine reduces resting variability, suggesting parasympathetic system dominance in regulating this variability during exercise.
Area of Science:
- Cardiovascular Physiology
- Equine Exercise Physiology
Background:
- Cardiac cycle length variability (CCLV) is a key indicator of autonomic nervous system function.
- Understanding CCLV in athletic animals like ponies is crucial for assessing physiological responses to exercise.
Purpose of the Study:
- To investigate the impact of strenuous exercise on CCLV in ponies.
- To determine the effect of atropine premedication on CCLV at rest and during exercise.
Main Methods:
- Measurements of cardiac cycle length, standard deviation (SDCL), and coefficient of variation (CVCL) were taken in ponies.
- Ponies were evaluated at rest and during strenuous exercise, both with and without atropine premedication.
Main Results:
- Exercise significantly reduced CCLV indexes (cardiac cycle length, SDCL, CVCL) in non-premedicated ponies.
- Atropine significantly decreased resting cardiac cycle length and variability indexes compared to non-premedicated values.
- Exercise after atropine reduced cardiac cycle length but did not significantly alter SDCL or CVCL.
Conclusions:
- Strenuous exercise nearly abolishes cardiac cycle length variability in ponies.
- Parasympathetic nervous system activity is the primary mediator of cardiac cycle length variability in ponies, particularly during exercise.