Muscle responses of thoroughbreds to conventional race training and detraining.

The research examined the physiological responses of muscles in ten thoroughbred horses to nine weeks of conventional race training and a subsequent six weeks of detraining. Findings show significant increases in specific muscle enzyme activities, glycogen concentration, and fiber areas with training, but no changes with detraining.

Study Design and Methods

• The study was conducted with ten healthy Thoroughbreds, previously trained, but in a sedentary state at the beginning of the study.
• These horses underwent conventional race training for nine weeks, followed by six weeks of detraining, which was essentially pasture rest.
• Muscle biopsy samples were obtained at three stages: prior to training, post-training, and after the six weeks of detraining. The sampled muscles were the right deltoid, triceps, vastus lateralis, middle gluteal, biceps femoris, and semitendinosus.
• These samples were then deeply frozen and analyzed for activities relating to various enzymes such as succinate dehydrogenase (SDH), 3-hydroxy-acylcoenzyme A dehydrogenase (HAD), and phosphorylase (PHOS). They were further analyzed for their glycogen concentration.

Results and Findings

• The analysis of the biopsy samples showed increases in SDH activities in the deltoid and vastus muscles, and HAD activities in the gluteal muscle in response to training. Deltoid muscle glycogen concentration also increased due to the training.
• No notable changes were observed in PHOS activity.
• Type-IIA1, -IIA2, and -IIA3 fiber areas in the triceps muscle increased in response to training. However, no changes were observed in the distribution of fiber types as a result of the training.
• No significant changes were observed in muscle enzyme activities, glycogen concentration, fiber types, and fiber areas from post-training to detraining.
• Further increases in SDH activity across multiple muscles, and in the glycogen concentration of the gluteal muscle, were observed when detraining values were compared with pretraining values.

Conclusion

• The study concluded that conventional race training led to noticeable physiological changes in horses’ muscle tissues, including increased activities of certain enzymes and glycogen concentrations.
• These changes may correlate with improved racing performance, making conventional race training a practical exercise regimen for Thoroughbreds.
• Interestingly, detraining seemed to not reverse these changes, as no significant differences were observed between post-training and detraining muscles. Even more, some benefits of training appeared to be retained, or even further amplified, during detraining.