Differences in the metabolic properties of gluteus medius and superficial digital flexor muscles and the effect of water treadmill training in the horse.

The research article explored the impact of water treadmill training on the metabolic properties of two horse muscles, gluteus medius and superficial digital flexor (SDF), and its consequences on their fatigue and risk of injury. It found no measurable change in multiple biochemical parameters in these muscles after water treadmill training, suggesting that a more strenuous training protocol may be required.

Introduction and Methodology

• The study was driven by a hypothesis that fitness training on a water treadmill might reduce the risk of tendon injuries in horses, which can occur as a result of fatigue in the flexor muscles.
• Five unfit but healthy horses were subjected to a water treadmill training regime, 5 days per week for 4 weeks. The daily workout started from 5 minutes and was gradually extended to 20 minutes a session.
• The horses’ gluteal and SDF muscles were biochemically analyzed before and after the 4-week training period. Specifically, resting muscle biopsies were used to measure glycogen, lactate, ATP, and glucose-6-phosphate (G6P) concentrations, as well as the activities of certain enzymes (citrate synthase (CS), 3-hydroxyacyl CoA dehydrogenase (HAD), and lactate dehydrogenase (LDH)).
• Additionally, the researchers conducted an incremental exercise test on a land treadmill to determine velocity at a heart rate of 200 beats per minute (V(200)), before and after the water treadmill regimen.

Results

• The water treadmill training did not result in any significant change in resting concentrations of muscle glycogen, lactamine, ATP, or G6P in either of the two muscles studied.
• Similarly, no measurable changes were noted in the enzymatic activities of CS, HAD, and LDH).
• The V(200) parameter was unchanged, which implies that the cardiocirculatory response to exercise was not significantly impacted by the training.
• The researchers found substantially lower concentrations (by 50%) of lactate, glycogen, G6P, and ATP in the SDF muscle compared to the gluteal muscle. This was coupled with a 30% higher percentage of type 1 muscle fibers in the SDF muscle.
• The activities of CS and HAD enzymes were found to be similar in the two muscles, but LDH activity was lower in the SDF muscle.

Conclusions

• The findings of this study suggest that the water treadmill training routine used was not strenuous enough to significantly impact the metabolic properties of the gluteal and SDF muscles in horses.
• The researchers argue that to achieve noticeable results, a more intense training protocol might be required.
• The low concentrations of certain substrates and the oxidative capacity of the SDF muscle may make this muscle more prone to catastrophic fatigue during high-intensity exercise, possibly leading to injuries. Providing these muscles with a form of resistance training could potentially mitigate this risk.