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The Journal of experimental biology1993; 179; 159-180; doi: 10.1242/jeb.179.1.159

Respiratory and cardiovascular adjustments during exercise of increasing intensity and during recovery in thoroughbred racehorses.

Abstract: A new design of flowmeter is described and used in a comprehensive study of the respiratory and cardiovascular adjustments that occur during a standardised exercise test in Thoroughbred horses. The flowmeter system and associated lightweight, fibreglass mask (total mass, 0.7 kg) have a maximum dead space of 500 ml and negligible resistance to airflow. They have no systematic effect on blood gases and, together with a rapidly responding mass spectrometer, enable an accurate computation of gas exchange to be performed together with breath-by-breath determination of other respiratory variables. At the highest level of exercise (12 ms-1 on a 3 degrees incline), the rate of oxygen uptake (VO2) and carbon dioxide production (VCO2) increased to 29.4 times and 36.8 times their resting values, respectively. Respiratory minute volume (VE) increased to 27.0 times its resting value, with respiratory frequency (fR) making the major contribution at the walk and trot. However, with increasing cantering speeds, fR changed little as it was locked in a 1:1 fashion to stride frequency, and tidal volume (VT) then made the major contribution to the increase in VE. The ratio of ventilatory dead space (VD) to VT in resting horses was lower than that previously reported in the literature and this could be the result of the different respiratory recording systems that were used. There was a close relationship between VT and stride length at increasing cantering speeds. Despite the fact that alveolar ventilation (VA) was well matched to VO2, there was a significant reduction in arterial PO2 (PaO2) when the horses cantered at 8 ms-1 and this eventually fell to 34% below the resting value. The present data tend to support the idea that VA/Vb (where Vb is cardiac output) inequalities are important in causing this hypoxaemia. However, the reduction in PaO2 was more than compensated for by an increase in haemoglobin concentration, [Hb], so the concentration of oxygen in the arterial blood (CaO2) was significantly above the resting value at all levels of exercise. Both lactate concentration and PaCO2 increased during exercise, causing substantial reductions in pH of both arterial and mixed venous blood. This would have inevitably shifted the oxygen equilibrium curve of the Hb to the right, desaturating the arterial blood and thus exacerbating the effect of the hypoxaemia, as would the almost 4 degrees C rise in blood temperature. The tight respiratory/locomotor linkage might prevent the acidosis and hyperthermia having the stimulatory effects on VE that they have in humans at high work loads.(ABSTRACT TRUNCATED AT 400 WORDS)
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Publication Date: 1993-06-01 PubMed ID: 8340728DOI: 10.1242/jeb.179.1.159Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

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 introduces a new flowmeter design for studying respiratory and cardiovascular changes in Thoroughbred horses during exercise and recovery. The flowmeter, paired with a lightweight fiberglass mask, allows for precise computation of gas exchange and observation of other respiratory variables. The primary findings note significant increases in oxygen uptake and carbon dioxide production during intense exercise, and a major reduction in arterial oxygen pressure compensated by increased hemoglobin concentration.

Methodology and Equipment

  • The researchers designed a new type of flowmeter and combined it with a lightweight fiberglass mask to monitor respiratory variables in Thoroughbred horses during a standardized exercise test.
  • This apparatus has a low resistance to airflow and minimal dead space enabling an accurate measurement of gas exchange.
  • Alongside a rapidly responding mass spectrometer, the research equipment provided breath-by-breath determination of additional respiratory factors.

Main Findings

  • The highest level of exercise led to an increase in the rate of oxygen uptake (VO2) and carbon dioxide production (VCO2)by 29.4 times and 36.8 times of the resting values respectively.
  • Respiratory minute volume (VE) also increased, with respiratory frequency (fR) contributing significantly to this during walking and trotting. This fR essentially synchronized with stride frequency during faster cantering,
  • The ratio of ventilatory dead space (VD) to tidal volume (VT) was lower than previously documented indicating that the recording systems might influence results.
  • The study noticed a correlation between stride length and tidal volume at varied cantering speeds.

Cardiovascular Adjustments

  • Despite the good match of alveolar ventilation (VA) to oxygen uptake (VO2), there was a considerable drop in arterial oxygen pressure (PaO2) when the horse sustained a canter at 8 ms-1. The researchers had expected an opposite result based on the effective VA/VO2 relation and believe that inequalities in the VA/cardiac output ratio might cause this unnatural hypoxemia.
  • The reduced PaO2 was counteracted by an increase in hemoglobin concentration, maintaining the oxygen concentration in the arterial blood (CaO2) well above resting value during all exercise intensities.

Blood Chemistry Changes

  • The research observed an increase in lactate concentration and arterial carbon dioxide pressure during exercise. These changes resulted in significant reductions in arterial and mixed venous blood pH which would eventually shift the oxygen equilibrium curve to the right, desaturating the arterial blood.

Conclusion

  • The researchers hypothesized that the physical linkage between respiration and locomotion might obstruct the acidosis and the increase in temperature from having the usual stimulating effects on VE, as observed in humans undertaking high-intensity tasks.

Cite This Article

APA
Butler PJ, Woakes AJ, Smale K, Roberts CA, Hillidge CJ, Snow DH, Marlin DJ. (1993). Respiratory and cardiovascular adjustments during exercise of increasing intensity and during recovery in thoroughbred racehorses. J Exp Biol, 179, 159-180. https://doi.org/10.1242/jeb.179.1.159

Publication

The Journal of experimental biology
ISSN: 0022-0949
NlmUniqueID: 0243705
Country: England
Language: English
Volume: 179
Pages: 159-180

Researcher Affiliations

Butler, P J
  • School of Biological Sciences, University of Birmingham, Edgbaston, UK.
Woakes, A J
    Smale, K
      Roberts, C A
        Hillidge, C J
          Snow, D H
            Marlin, D J

              MeSH Terms

              • Animals
              • Cardiac Output
              • Cardiovascular Physiological Phenomena
              • Female
              • Heart Rate
              • Horses / physiology
              • Hydrogen-Ion Concentration
              • Lactates / blood
              • Lactic Acid
              • Male
              • Oxygen / blood
              • Oxygen Consumption
              • Physical Exertion / physiology
              • Respiration / physiology
              • Rheology / instrumentation

              Citations

              This article has been cited 23 times.
              1. Brownlow M, Mizzi JX. An Overview of Exertional Heat Illness in Thoroughbred Racehorses: Pathophysiology, Diagnosis, and Treatment Rationale. Animals (Basel) 2023 Feb 9;13(4).
                doi: 10.3390/ani13040610pubmed: 36830397google scholar: lookup
              2. Kozłowska N, Wierzbicka M, Jasiński T, Domino M. Advances in the Diagnosis of Equine Respiratory Diseases: A Review of Novel Imaging and Functional Techniques. Animals (Basel) 2022 Feb 4;12(3).
                doi: 10.3390/ani12030381pubmed: 35158704google scholar: lookup
              3. Bukhari SSUH, McElligott AG, Parkes RSV. Quantifying the Impact of Mounted Load Carrying on Equids: A Review. Animals (Basel) 2021 May 7;11(5).
                doi: 10.3390/ani11051333pubmed: 34067208google scholar: lookup
              4. Léguillette R, Bond SL, Lawlor K, Haan T, Weber LM. Comparison of physiological demands in Warmblood show jumping horses over a standardized 1.10 m jumping course versus a standardized exercise test on a track. BMC Vet Res 2020 Jun 8;16(1):182.
                doi: 10.1186/s12917-020-02400-9pubmed: 32513241google scholar: lookup
              5. Katz LM, Stallard J, Holtby A, Hill EW, Allen K, Sweeney J. Inspiratory muscle training in young, race-fit Thoroughbred racehorses during a period of detraining. PLoS One 2020;15(4):e0225559.
                doi: 10.1371/journal.pone.0225559pubmed: 32275657google scholar: lookup
              6. Meir JU, York JM, Chua BA, Jardine W, Hawkes LA, Milsom WK. Reduced metabolism supports hypoxic flight in the high-flying bar-headed goose (Anser indicus). Elife 2019 Sep 3;8.
                doi: 10.7554/eLife.44986pubmed: 31478481google scholar: lookup
              7. Curtin NA, Bartlam-Brooks HLA, Hubel TY, Lowe JC, Gardner-Medwin AR, Bennitt E, Amos SJ, Lorenc M, West TG, Wilson AM. Remarkable muscles, remarkable locomotion in desert-dwelling wildebeest. Nature 2018 Nov;563(7731):393-396.
                doi: 10.1038/s41586-018-0602-4pubmed: 30356212google scholar: lookup
              8. Brkljača Bottegaro N, Gotić J, Šuran J, Brozić D, Klobučar K, Bojanić K, Vrbanac Z. Effect of prolonged submaximal exercise on serum oxidative stress biomarkers (d-ROMs, MDA, BAP) and oxidative stress index in endurance horses. BMC Vet Res 2018 Jul 6;14(1):216.
                doi: 10.1186/s12917-018-1540-ypubmed: 29980209google scholar: lookup
              9. Mellor DJ, Beausoleil NJ. Equine Welfare during Exercise: An Evaluation of Breathing, Breathlessness and Bridles. Animals (Basel) 2017 May 26;7(6).
                doi: 10.3390/ani7060041pubmed: 28587125google scholar: lookup
              10. Stefánsdóttir GJ, Gunnarsson V, Roepstorff L, Ragnarsson S, Jansson A. The effect of rider weight and additional weight in Icelandic horses in tölt: part I. Physiological responses. Animal 2017 Sep;11(9):1558-1566.
                doi: 10.1017/S1751731117000556pubmed: 28320488google scholar: lookup
              11. Minami Y, Kawai M, Migita TC, Hiraga A, Miyata H. Free radical formation after intensive exercise in thoroughbred skeletal muscles. J Equine Sci 2011;22(2):21-8.
                doi: 10.1294/jes.22.21pubmed: 24833984google scholar: lookup
              12. Hawkes LA, Butler PJ, Frappell PB, Meir JU, Milsom WK, Scott GR, Bishop CM. Maximum running speed of captive bar-headed geese is unaffected by severe hypoxia. PLoS One 2014;9(4):e94015.
                doi: 10.1371/journal.pone.0094015pubmed: 24710001google scholar: lookup
              13. Brown BN, Siebenlist NJ, Cheetham J, Ducharme NG, Rawlinson JJ, Bonassar LJ. Computed tomography-guided tissue engineering of upper airway cartilage. Tissue Eng Part C Methods 2014 Jun;20(6):506-13.
                doi: 10.1089/ten.TEC.2013.0216pubmed: 24164398google scholar: lookup
              14. Grevemeyer B, Bogdanovic L, Canton S, St Jean G, Cercone M, Ducharme NG, Brown BN. Regenerative medicine approach to reconstruction of the equine upper airway. Tissue Eng Part A 2014 Apr;20(7-8):1213-21.
                doi: 10.1089/ten.TEA.2013.0217pubmed: 24160675google scholar: lookup
              15. Cheetham J, Regner A, Jarvis JC, Priest D, Sanders I, Soderholm LV, Mitchell LM, Ducharme NG. Functional electrical stimulation of intrinsic laryngeal muscles under varying loads in exercising horses. PLoS One 2011;6(8):e24258.
                doi: 10.1371/journal.pone.0024258pubmed: 21904620google scholar: lookup
              16. Choi EY, Jang JY, Cho YO. Coffee intake can promote activity of antioxidant enzymes with increasing MDA level and decreasing HDL-cholesterol in physically trained rats. Nutr Res Pract 2010 Aug;4(4):283-9.
                doi: 10.4162/nrp.2010.4.4.283pubmed: 20827343google scholar: lookup
              17. Yamamoto M, Kato A, Ropert-Coudert Y, Kuwahara M, Hayama S, Naito Y. Evidence of dominant parasympathetic nervous activity of great cormorants (Phalacrocorax carbo). J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2009 Apr;195(4):365-73.
                doi: 10.1007/s00359-009-0414-ypubmed: 19198851google scholar: lookup
              18. Lafortuna CL, Saibene F, Albertini M, Clement MG. The regulation of respiratory resistance in exercising horses. Eur J Appl Physiol 2003 Oct;90(3-4):396-404.
                doi: 10.1007/s00421-003-0925-0pubmed: 12920523google scholar: lookup
              19. Lafortuna CL, Reinach E, Saibene F. The effects of locomotor-respiratory coupling on the pattern of breathing in horses. J Physiol 1996 Apr 15;492 ( Pt 2)(Pt 2):587-96.
                doi: 10.1113/jphysiol.1996.sp021331pubmed: 9019552google scholar: lookup
              20. Mills PC, Smith NC, Casas I, Harris P, Harris RC, Marlin DJ. Effects of exercise intensity and environmental stress on indices of oxidative stress and iron homeostasis during exercise in the horse. Eur J Appl Physiol Occup Physiol 1996;74(1-2):60-6.
                doi: 10.1007/BF00376495pubmed: 8891501google scholar: lookup
              21. Mills PC, Marlin DJ, Demoncheaux E, Scott C, Casas I, Smith NC, Higenbottam T. Nitric oxide and exercise in the horse. J Physiol 1996 Sep 15;495 ( Pt 3)(Pt 3):863-74.
                doi: 10.1113/jphysiol.1996.sp021638pubmed: 8887788google scholar: lookup
              22. Boesch JM, Gleed RD, Buss PE, Tordiffe ASW, Zeiler GE, Miller MA, Viljoen F, Harvey BH, Parry SA, Meyer LCR. Etorphine induces pathophysiology in immobilized white rhinoceros through sympathomimesis that is attenuated by butorphanol. Conserv Physiol 2025;13(1):coaf009.
                doi: 10.1093/conphys/coaf009pubmed: 40196708google scholar: lookup
              23. Fahlman A. Cardiorespiratory adaptations in small cetaceans and marine mammals. Exp Physiol 2024 Mar;109(3):324-334.
                doi: 10.1113/EP091095pubmed: 37968859google scholar: lookup
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