The physiological and biochemical response of standardbred horses to exercise of varying speed and duration
Lindholm, A.; Saltin, B.
Acta Veterinaria Scandinavica 15(3): 310-324
1974
ISSN/ISBN: 0044-605X PMID: 4416409 Document Number: 72676
The effects of trotting for 3.3-12.5 m per sec for 400-2000 m, continuous trotting for 1-2 hours, and racing were studied in clinically healthy standardbred horses aged 4-8 years in good training condition. Temperature and heart rate were measured, and blood and muscle biopsy samples were taken in the 5-min rest intervals between work bouts and at the end of each exercise. Mean muscle temperature, which was 37 deg C at rest, increased to 41 deg C after the highest trotting speed and racing, and heart rate increased from 40 to 140 beats/min in most of the tests, but rose to 240 beats in racing and at close to maximal trotting speed maintained for at least 700 m. Muscle and blood lactate values increased and glycogen levels decreased rapidly near maximal speed, although critically low levels were never reached. Further evidence of increased glycolysis during racing was the 8-10 fold increase in glucose-6-phosphate levels found in muscle immediately after a race. It is concluded that a number of short training bouts would be preferable to a single long exercise period, and that six 1000 m trots at close to maximal speeds produced stresses similar to those of racing.