• horse;
  • maximum oxygen uptake;
  • echocardiography;
  • heart size


  1. Top of page
  2. Summary
  3. References

Maximum oxygen uptake also appears to correlate to athletic performance in horses. In the Thoroughbred industry, there has long been an empirical theory that heart size is related to athletic performance, despite a lack of scientific evidence supporting this assertion. To investigate the relationship between peak oxygen consumption (V̇O2max) and cardiac size measured by echocardiography, guided M-mode and 2-dimensional echocardiography were performed in 17 conditioned Thoroughbreds with a range of V̇O2max from 126 to 217 ml/min/kg STPD (mean ± s.d. 158 ± 28 ml/min/kg). Horses were age 2–10 years and weighed 430–510 kg. Echocardiography was performed using a Vingmed System V echocardiograph with a 2.25 MHz phased array ultrasound transducer. All images were obtained from the right hemithorax using a short axis view of the left ventricle (LV) at the level of the chordae tendinae. All horses were free from significant regurgitation at the aortic or mitral valves. Maximal oxygen uptake was measured during a standardised incremental treadmill exercise test to fatigue. Maximal oxygen uptake was correlated significantly with LVIDd (r = 0.71; P = 0.001), MWT (r = 0.72; P = 0.001), LV mass (r = 0.78; P = 0.0002) and LV short-axis area (r = 0.69; P = 0.003). When indices of heart size were indexed to bodyweight, the correlation between V̇O2max and indices of heart size were LVIDd (r = 0.57; P = 0.01), MWT (r = 0.44; P = 0.07), LV mass (r = 0.78; P = 0.0002) and LV short-axis area (r = 0.69; P = 0.003). The current study suggests there is a strong relationship between V̇O2max and measurements of left ventricular size in Thoroughbred horses when individuals with a range of V̇O2max are compared.




Motion mode


Left ventricular internal diameter at end-diastole


Left ventricular internal diameter in systole


Interventricular septal thickness at end-diastole


Interventricular septal thickness in systole


Left ventricular free wall thickness at end-diastole


Mean left ventricular free wall thickness at end-diastole


Maximum oxygen uptake

LV mass

Calculated left ventricular muscle mass


Standard temperature and pressure, dry


  1. Top of page
  2. Summary
  3. References
  • Al-Hazzaa, H.M. and Chukwuemeka, A.C. (2001) Echocardiographic dimensions and maximal oxygen uptake in elite soccer players. Saudi med. J. 22, 320325.
  • Blimkie, C.J., Cunningham, D.A. and Nichol, P.M. (1980) Gas transport capacity and echocardiographically determined cardiac size in children. J. appl. Physiol. 49, 994999.
  • Bonagura, J.D. (1994) Equine echocardiography. Br. vet. J. 150, 503506.
  • Butler, P.J., Woakes, A.J., Smale, K., Roberts, C.A., Hillidge, C.J., Snow, D.H. and Marlin, D.J. (1993) Respiratory and cardiovascular adjustments during exercise of increasing intensity and during recovery in the thoroughbred racehorse. J. expt. Biol. 179, 159180.
  • Devereux, R.B. and Reichek, N. (1977) Echocardiographic estimation of ventricular mass in man: anatomic validation of the method. Circulation 55, 613618.
  • Fagard, R.H. (1996) Athlete's heart: a meta-analysis of the echocardiographic experience. Int. J. sports Med. 17, Suppl. 3, S140S144.
  • Fagard, R.H. (1997) Impact of different sports and training on cardiac structure and function. Cardiol. Clin. 15, 397412.
  • Gauvreau, G.M., Staempfli, H., McCutcheon, L.J., Young, S.S. and McDonell, W.N. (1995) Comparison of aerobic capacity between racing standardised horses. J. appl. Physiol. 78, 14471451.
  • Gilbert, C.A., Nutter, D.O., Felner, J.M., Perkins, J.V., Heymsfield, S.B. and Schlant, R.C. (1977) Echocardiographic study of cardiac dimensions and function in the endurance-trained athlete. Am. J. Cardiol. 40, 528533.
  • Harkins, J.D., Beadle, R.E. and Kamerling, S.G. (1993) The correlation of running ability and physiological variables in Thoroughbred racehorses. Equine vet. J. 25, 5360.
  • Leadon, D., McAllister, H., Mullins, E. and Osborne, M. (1991) Electrocardiographic and echocardiographic measurements and their relationships in Thoroughbred yearlings to subsequent performance In: Equine Exercise Physiology 3, Eds: S.G.B.Persson, A.Lindholm and L.B.Jeffcott. ICEEP Publications, Davis, California. pp 188195.
  • Long, K.J. (1992) Two-dimensional and M-mode echocardiography. Equine vet. Educ. 4, 303310.
  • Long, K.J., Bonagura, J.D. and Darke, P.G.G. (1992) Standardised imaging technique for guided M-mode and Doppler echocardiography in the horse. Equine vet. J. 24, 226235.
  • Marr, C.M. (1994) Equine echocardiography-sound advice at the heart of the matter. Br. vet. J. 150, 527545.
  • Moodie, E.W. and Sheard, R.P. (1980) The use of electrocardiography to estimate heart weight and predict performance in the racehorse. Aust. vet. J. 56, 557558.
  • O'Callaghan, M.W. (1985) Comparison of echocardiographic and autopsy measurements of cardiac dimensions in the horse. Equine vet. J. 17, 361368.
  • Osborne, G., Wolfe, L.A., Burggraf, G.W. and Norman, R. (1992) Relationships between cardiac dimensions, anthropometric characteristics and maximal aerobic power (Vo2max) in young men. Int. J. sports Med. 13, 219224.
  • Patteson, M.W., Gibbs, C., Wotton, P.R. and Cripps, P.J. (1995) Echocardiographic measurements of cardiac dimensions and indices of cardiac function in normal adult Thoroughbred horses. Equine vet. J., Suppl. 19, 1827.
  • Pluim, B.M., Zwinderman, A.H., Van der Laarse, A. and Van der Wall, E.E. (2000) The athlete's heart. A meta-analysis of cardiac structure and function. Circulation 101, 336344.
  • Reef, V.B. (1995) Heart murmurs in horses: determining their significance with echocardiography. Equine vet. J., Suppl. 19, 7180.
  • Sampson, S.N., Tucker, R.L. and Bayly, W.M. (1999) Relationship between Vo2max, heart score and echocardiographic measurements obtained at rest and immediately following maximal exercise in Thoroughbred horses. Equine vet. J., Suppl. 30, 190194.
  • Weyman, A.E. (1994) Cross-sectional scanning: technical principles and instrumentation. In: Principles and Practice of Echocardiography, 2nd edn., Ed: A.E.Weyman, Lea and Febiger, Philadelphia. pp 2956.
  • Wieling, W., Borghols, E.A., Hollander, A. P., Danner, S.A. and Dunning, A.J. (1981) Echocardiographic dimensions and maximal oxygen uptake in oarsmen during training. Br. heart J. 46, 190195.
  • Wilmore, J.H. and Costill, D.L. (1994) Cardiorespiratory adaptations to training. In: Physiology of Sport and Exercise, Eds: J.H.Wilmore and D.L.Costill. Human Kinetics, Illinois, USA. pp 214238.
  • Woakes, A.J., Butler, P.J. and Snow, D.H. (1987) The measurement of respiratory airflow in exercising horses. In: Equine Exercise Physiology 2, Eds: J.R.Gillespie and N.E.Robinson. ICEEP Publications, Davis, California, pp 194205.
  • Young, L.E. (1999) Cardiac responses to training in 2-year-old Thoroughbreds: an echocardiographic study. Equine vet. J. 30, 195198.
  • Young, L.E. and Scott, G.R. (1998) Measurement of cardiac function by transthoracic echocardiography: day to day variability and repeatability in Thoroughbred horses. Equine vet. J. 30, 117122.
  • Young, L.E. and Wood, J.L.N. (2000) The effects of age and training on murmurs of atrioventricular valvular regurgitation in young Thoroughbreds. Equine vet. J. 32, 195199.
  • Young, L. E. and Wood, J. L. N. (2001) Effect of age and training on Thoroughbred valvular competence. Proc. Am. Coll. vet. med. Forum 19, 9395.