Muscle metabolic responses to maximal exercise in standardbred trotters and effects of creatine and bicarbonate administrationSchuback, Katarina
The principal aim of this investigation was to introduce a protocol for standardised maximal treadmill exercise for the horse that would induce an anaerobic metabolic response and to find reproducible markers in plasma for anaerobic metabolism, specifically for adenine nucleotide degradation. A further aim was to determine whether the muscle metabolic response during exercise influences the locomotion pattern of the horse. This test was also used to examine the effects of administration of creatine and sodium bicarbonate on muscle metabolism and/or performance. A study was also performed to find out whether plasma total carbon dioxide can be measured under post-race conditions as an indicator of pre-race bicarbonate administration.
Horses performed an incremental maximal treadmill exercise test in one-minute steps until they no longer could keep pace with the treadmill. Biopsy specimens were collected from the gluteus medius muscle at rest, immediately post-exercise and after 15 minutes of recovery. Blood samples were collected at rest, during exercise, immediately post-exercise and atfrequent intervals during recovery. The exercise test induced an anaerobic metabolic response, as ATP, creatine phosphate (CP) and glycogen decreased and ADP, AMP, inosine monophosphate (IMP) and lactate concentrations increased in muscle after termination of exercise. Plasma lactate concentrations increased during exercise and early recovery and plasma hypoxanthine, xanthine and uric acid concentrations increased during recovery. The test was found to give reproducible results. There was a negative correlation between the increase in muscle ADP post-exercise and the stride frequency close to fatigue. Plasma uric acid post-exercise was related to adenine nucleotide degradation in muscle during exercise. Duration of exercise was related to increase in muscle IMP, AMP and lactate and to change in peak plasma uric acid, indicating the importance of anaerobic metabolism and adenine nucleotide degradation for maximal performance. Neither administration of bicarbonate nor of creatine was found to influence muscle metabolism. Results from a simulated race showed that in all horses given bicarbonate pre-race the total carbon dioxide concentration was above 37 mmol/13 hours post-race.
In conclusion, the duration of exercise during a maximal test seems to be dependent on the anaerobic metabolic response, and the degradation of adenine nucleotides can be estimated by measuring plasma uric acid during recovery. Neither administration of bicarbonate nor of creatine affects the muscle metabolic response during the maximal exercise test. Post-race plasma carbon dioxide can be used as an indicator of bicarbonate administration pre-race.
Keywordshorse; exercise; anaerobic metabolism; creatine; bicarbonate
Published inActa Universitatis Agriculturae Sueciae. Veterinaria
2000, number: 83
Publisher: Swedish University of Agricultural Sciences