Exercise training increases oxidative capacity and attenuates exercise-induced ultrastructural damage in skeletal muscle of aged horses.

The research article explores how intense aerobic exercise training can benefit aged horses by improving their endurance, aerobic capacity, and muscle oxidative capacity, along with reducing their vulnerability to exercise-induced muscle cell damage. Yet, it was noted that these adaptive responses might vary across different muscle groups.

Objective of the Study

• The study aimed to determine the impact of a 10-week treadmill exercise training program on the oxidative capacity of skeletal muscle and the degree of exercise-induced ultrastructural muscle damage in aged female Quarter horses.

Methodology

• They subjected six aged female Quarter horses to an incremental exercise test before and after the training program.
• They studied the ultrastructural muscle damage by performing an electron microscopic examination of triceps, semimembranosus, and masseter muscle samples.

Findings

• The researchers found that the horses’ maximum aerobic capacity increased by 22% after completing the exercise training program.
• There were changes in muscle composition observed: the proportion of type IIa myosin heavy chain increased in the semimembranosus muscle, and the proportion of type IIx myosin heavy chain decreased in the triceps muscle.
• The triceps muscle displayed significant increases in both citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase activities, which are critical enzymes for aerobic metabolism, indicating heightened muscle oxidative capacity.
• Upon post-training evaluation, there was a noticeable decrease in the severity of exercise-induced ultrastructural muscle damage in the semimembranosus muscle at both the same absolute and relative workloads.

Conclusion

• The study revealed that aged horses show a notable capacity to adapt to intense aerobic exercise training, exhibiting improvements in endurance, overall body aerobic capacity, and muscle oxidative capacity, and were less susceptible to exercise-induced muscle cell damage.
• However, the researchers noted that these adaptations might be muscle group-specific, indicating the need for further research to understand the extent and specificity of these adaptive responses across different muscles.