45 Campbell Drive, Walroonga, NSW 2075, Australia.
Effects of high-intensity exercise on plasma catecholamines in the Thoroughbred horse
Article first published online: 23 APR 2010
© 1992 EVJ Ltd
Equine Veterinary Journal
Volume 24, Issue 6, pages 462–467, November 1992
How to Cite
SNOW, D. H., HARRIS, R. C., MACDONALD, I. A., FORSTER, C. D. and MARLIN, D. J. (1992), Effects of high-intensity exercise on plasma catecholamines in the Thoroughbred horse. Equine Veterinary Journal, 24: 462–467. doi: 10.1111/j.2042-3306.1992.tb02877.x
- Issue published online: 23 APR 2010
- Article first published online: 23 APR 2010
- Received 13.1.92; accepted 31.5.92
- plasma catecholamines
In Study 1, a single speed test of 6 to 12 m/sec was performed for 2 mins at an incline of 5° on a high-speed treadmill (single-step test). Only one speed was performed per session and blood samples were taken before and after the test. In Study 2 horses cantered for 1 min at increasing speeds of 6 to 13 m/sec on an incline of 3° (multiple-step test). Blood samples were taken before exercise, throughout the test and during recovery.
In the single-step test plasma concentrations of adrenaline and noradrenaline both increased at speeds of 9 m/sec, as did blood lactate. Mean concentrations of adrenaline and noradrenaline at the end of the 12 m/sec test were 153 and 148 nmol/litre, respectively. Plasma concentrations were similar over all speeds although there was a tendency for the increase in noradrenaline to be greater than that of adrenaline at the lower speeds. The multiple-step test resulted in smaller increases in both adrenaline and noradrenaline. Although again closely correlated, increases in adrenaline were 20–30% greater than those for noradrenaline.
In both exercise models, changes in plasma adrenaline and noradrenaline values with exercise showed an exponential relationship to plasma lactate. A plasma half-life of less than 30 secs was indicated during recovery from the multiple-step test. Changes in adrenaline and noradrenaline were much greater than previously recorded in man and emphasise the importance of catecholamines in mediating the physiological response of the horse to exercise.