Effect of Exercise Intensity and Repetition on Heart Rate Variability During Training in Elite Trotting Horse

Abstract

RR intervals of ten elite trotting horses were recorded during an interval training session performed on track. This study examined two hypotheses. Firstly, like in humans, the hyperpnea combined with a decrease in cardiac autonomic control on heart rate during heavy exercise could result in a prevalence of high frequency heart rate variability. Secondly, this prevalence could increase with the heavy exercise repetition. Two exercise intensities were compared: moderate (ME) and heavy (HE). Furthermore, heavy exercise repetitions were compared between the beginning and the end of the interval training session. When comparing ME and HE periods: heart rate was significantly lower (155 ± 12 vs. 210 ± 9 ms, p < 0.001), LF spectral energy (0.04 - 0.2 Hz) was significantly higher (ME: 6.94 ± 4.80 and HE: 0.24 ± 0.14 ms² · Hz^-1, p < 0.001) whereas HF (0.2 - 2 Hz) was significantly lower (ME: 7.09 ± 2.24 and HE: 10.60 ± 3.64 ms² · Hz^-1, p < 0.05). In relative terms, ME showed similar results in both LFn (LF/LF+HF) and HFn (HF/LF+HF) whereas HE showed a large prevalence of HFn energy compared to LFn (p < 0.001). The difference in LF/HF ratio between the two exercise conditions was significant (1.14 ± 0.92 vs. 0.09 ± 0.12, p < 0.001). Exercise repetition induced a significant increase in heart rate between the beginning and the end of the interval training session (207 ± 10 beats · min^-1 vs. 212 ± 9 beats · min^-1, p < 0.001) whereas LF energy decreases (1.54 ± 1.65 vs. 0.32 ± 0.24 ms² · Hz^-1, p < 0.01) and HF energy remained constant (10.79 ± 4.10 vs. 10.40 ± 3.35 ms² · Hz^-1, NS). This study confirmed the results observed in humans during heavy exercise conditions with a large prevalence of HF in contrast to LF, this prevalence increasing with exercise repetitions. The observed decrease in LF/HF ratio could provide an index of hyperpnea in horses during interval training.

Key words

Equine exercise response - interval training - cardio-respiratory interactions - Fast Fourier Transform - Smoothed Pseudo Wigner Ville Distribution

References

• 1 Akselrod S, Eliash S, Oz O, Cohen S. Hemodynamic regulation in SHR: investigation by spectral analysis.  Am J Physiol. 1987;  253 176-183
• 2 Arai Y, Saul J P, Albrecht P, Hartley L H, Lilly L S, Cohen R J, Colucci W. Modulation of cardiac autonomic activity during and immediately after exercise.  Am J Physiol. 1989;  256 132-141
• 3 Art T, Desmecht D, Amory H, Lekeux P. Synchronization of locomotion and respiration in trotting ponies.  J Vet Med. 1990;  37 95-103
• 4 Aubert A E, Seps B, Beckers F. Heart rate variability in athletes.  Sports Med. 2003;  33 889-919
• 5 Barrey E. Modélisation de la dépense énergétique du trotteur à l'entraînement et en course.  EquAthlon. 1993;  5 16-19
• 6 Barrey E, Couroucé A, d'Orsetti H, Evans D, Roberts C, Rose J R. Couplage de la ventilation respiratoire avec la locomotion du cheval de course.  EquAthlon. 2000;  30 32-35
• 7 Berger R D, Saul J P, Cohen R J. Transfer function analysis of autonomic regulation. I. Canine atrial rate response.  Am J Physiol. 1989;  256 142-152
• 8 Bernardi L, Salvucci F, Suardi R, Solda P L, Calciati A, Perlini S, Falcone C, Ricciardi L. Evidence for an intrinsic mechanism regulating heart rate variability in transplanted and the intact heart during submaximal dynamic exercise.  Cardiovasc Res. 1990;  24 969-981
• 9 Bernardi L, Keller F, Sanders M, Reddy P S, Griffith B, Meno F, Pinsky M R. Respiratory sinus arrhythmia in the denervated heart.  J Appl Physiol. 1989;  67 1447-1455
• 10 Casadei B, Moon J, Johnston J, Caiazza A, Sleight P. Is respiratory sinus arrhythmia a good index of cardiac vagal tone in exercise?.  J Appl Physiol. 1996;  81 556-564
• 11 Casadei B, Cochrane S, Johnston J, Conway J, Sleight P. Pitfalls in the interpretation of spectral analysis of heart rate variability during exercise in humans.  Acta Physiol Scand. 1995;  153 125-131
• 12 Clément F, Barrey E. Heart rate fluctuations in the horse at rest: (1) Investigation of heart rate changes by spectral analysis.  C R Acad Sci III. 1995;  318 859-865
• 13 Cottin F, Médigue C, Leprêtre P M, Papelier Y, Koralsztein J P, Billat V L. Heart rate variability during exercise performed below and above ventilatory threshold.  Med Sci Sports Exerc. 2004;  36 594-600
• 14 Cottin F, Durbin F, Papelier Y. Heart rate variability during cycloergometric exercise or judo wrestling eliciting the same heart rate level.  Eur J Appl Physiol. 2004;  91 177-184
• 15 Cottin F, Papelier Y, Escourrou P. Effects of exercise load and breathing frequency on heart rate and blood pressure variability during dynamic exercise.  Int J Sports Med. 1999;  20 1-7
• 16 Eckberg D L. Sympatho-vagal balance: a critical appraisal.  Circulation. 1997;  96 3224-3232
• 17 Gottlieb M, Essén-Gustavsson B, Lindholm A, Persson G B. Circulatory and muscle metabolic responses to draught work compared to increasing trotting velocities.  Equine Vet J. 1988;  20 430-434
• 18 Harris F J. On the use of windows for harmonic analysis with the discrete Fourier Transform.  Proc IEEE. 1978;  66 51-83
• 19 Hirsch J A, Bishop B. Respiratory sinus arrythmia in humans: how breathing pattern modulates heart rate.  Am J Physiol. 1981;  241 620-629
• 20 Hörnicke H, Meisner R, Pollmam U. Respiration in exercising horses. Snow DH, Persson SGB, Rose RJ Equine Exercise Physiology. Cambridge; Granta Editions 1987: 7-12
• 21 Japundzic N, Grichois M L, Zitoun P, Laude D, Elghozi J L. Spectral analysis of blood pressure and heart rate in conscious rats: effects of autonomic blockers.  J Auton Nerv Sys. 1990;  30 91-100
• 22 Johnston C, Gottlieb-Vedi M, Drevemo S, Roepstorff L. The kinematics of loading and fatigue in the standardbred trotter.  Equine Vet J Suppl. 1999;  30 249-253
• 23 Kohl P, Hunter P, Noble D. Stretch-induced changes in heart rate and rhythm: clinical observations, experiments, and mathematical models.  Prog Biophys Mol Biol. 1999;  71 91-138
• 24 Kohl P, Kamkin A G, Kiseleva S, Streubel T. Mechanosensitive cells in the atrium of frog heart.  Exp Physiol. 1992;  77 213-216
• 25 Kuwahara M, Hiraga A, Kai M, Tsubone H, Sugano S. Influence of training on autonomic nervous function in horses: evaluation by power spectral analysis of heart rate variability.  Equine Vet J. 1999;  30 (Suppl) 178-180
• 26 Kuwahara M, Hashimoto S, Ishii K, Yagi Y, Hada T, Hiraga A, Kai M, Kubo K, Oki H, Tsubone H, Sugano S. Assessement of autonomic nervous function by power spectral analysis of heart rate variability in the horse.  J Auton Nerv Sys. 1996;  60 43-48
• 27 Leach D H, Cymbaluk N E. Relationship between stride length, stride frequency, velocity and morphometrics of foals.  Am J Vet Res. 1986;  47 2090-2097
• 28 Leach D H, Springings E J. Gait fatigue in the racing Thoroughbred.  J Equine Med Surg. 1979;  3 436-443
• 29 Lombardi F, Montano N, Finocchiaro M L, Ruscone T G, Baselli G, Cerutti S, Malliani A. Spectral analysis of sympathetic discharge in decerebrate cats.  J Auton Nerv Sys. 1990;  30 97-100
• 30 Mc Donough P, Kindig C A, Erickson H H, Poole D C. Mechanistic basis for the gas exchange threshold in thoroughbred horses.  J Appl Physiol. 2001;  92 1499-1505
• 31 Macor F, Fagard R, Amery A. Power spectral analysis of RR interval and blood pressure short-term variability at rest and during dynamic exercise: comparison between cyclists and controls.  Int J Sports Med. 1996;  17 175-181
• 32 Monti A, Médigue C, Mangin L. Instantaneous parameter estimation in cardiovascular time series by harmonic and time-frequency analysis.  IEEE Trans Biomed Eng. 2002;  49 1547-1556
• 33 Padilla D J, McDonough P, Kindig C A, Erickson H H, Poole D C. Ventilatory dynamics and control of blood gases following maximal exercise in the thoroughbred horse.  J Appl Physiol. 2004;  96 2187-2193
• 34 Pagani M, Lombardi F, Guzzetti S, Rimoldi O, Furlan R, Pizzinelli P, Sandrone G, Malfatto G, Dell'orto S, Piccaluga E, Turiel M, Baselli G, Cerutti S, Malliani A. Power spectral analysis of heart rate and arterial pressure variabilities as a marker of sympatho-vagal interaction in man and conscious dog.  Circ Res. 1986;  59 178-193
• 35 Pelletier N, Leith D E. Ventilation and carbon dioxide exchange in exercising horses: effect of inspired oxygen fraction.  J Appl Physiol. 1995;  78 654-662
• 36 Persson S GB. Evaluation of exercise tolerance and fitness in the performance horse. Snow DH, Persson SGB, Rose RJ Equine Exercise Physiology. Cambridge; Granta Publications 1983: 441-457
• 37 Physick-Sheard P W, Marlin D J, Thornill R, Schroter R C. Frequency domain analysis of heart rate variability in horses at rest and during exercise.  Equine vet J. 2000;  32 253-262
• 38 Pola S, Macerata A, Emdin M, Marchesi C. Estimation of the power spectral density in non-stationary cardiovascular time series: assessing the role of the time-frequency representations (TFR).  IEEE Trans Biomed Eng. 1996;  43 46-57
• 39 Rowell L B. Human Cardiovascular Control. New York; Oxford University Press 1993: 42-43
• 40 Task force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology . Heart rate variability. Standards of measurement, physiological interpretation, and clinical use.  Circulation. 1996;  93 1043-1065
• 41 Thayer J F, Hahn A W, Pearson M A, Sollers 3rd J J. Heart rate variability during exercise in the horse.  Biomed Sci Instrum. 1997;  34 246-251
• 42 Toska K, Eriksen M. Respiration-synchronous fluctuations in stroke volume, heart rate and arterial pressure in humans.  J Physiol. 1993;  472 501-512
• 43 Valette J P, Barrey E, Garbasi C, Wolter R. Estimation du seuil anaérobie chez le poney.  Ann Zootech. 1989;  38 229-236
• 44 Visser E K, van Reenen C G, van der Werf J T, Schilder M B, Knaap J H, Barneveld A, Blokhuis H J. Heart rate and heart rate variability during a novel object test and a handling test in young horses.  Physiol Behav. 2002;  76 289-296
• 45 Voss B, Mohr E, Krzywanek H. Effects of aqua-treadmill exercise on selected blood parameters and on heart-rate variability of horses.  J Vet Med A Physiol Pathol Clin Med. 2002;  49 137-143