Effect of different blood-guided conditioning programmes on skeletal muscle ultrastructure and histochemistry of sport horses.

The research explores the impact of three different exercise programmes on the muscular structure of young sport horses. The results suggest that low to moderate intensity exercises for longer durations are most effective in improving muscle characteristics related to stamina and power.

Methods

• The researchers used six non-trained 2-year-old Haflinger horses for the study.
• The horses were subjected to three different lactate-guided exercise intensity levels: velocities inducing blood lactate concentrations of 1.5 (v1.5), 2.5 (v2.5), and 4 (v4) mm respectively.
• For each intensity level, the exercise duration was either 25 or 45 minutes.
• Each exercise programme lasted for 6 weeks and was followed by a 5-week rest period.
• Before, after, and during the rest period, muscle biopsies from the horse’s gluteus medius muscle were collected and analysed.

Findings

• The analysis showed that all training and detraining adaptations were similar in nature, but showed variation in magnitude according to the different exercise programmes.
• The adaptations observed in the horses’ muscle tissue included significant increases in the size of their mitochondria and myofibrils (both responsible for energy production) and hypertrophy (enlargement) of myofibrillar ATPase type IIA muscle fibers (associated with speed).
• There was also a noticeable reduction in the number of type IIx low-oxidative fibers, which are less efficient at utilizing oxygen.
• Overall, these changes suggest an improvement in both muscle aerobic capacity and muscle strength.
• The effects were more significant when using v1.5 and v2.5 as the exercise intensities for 45 minutes, whereas conditioning horses at v4 for 25 minutes resulted in minimal changes.
• Most of these muscular modifications returned towards their pre-conditioning status after 5 weeks without conditioning.

Conclusion

• The findings suggest that low to moderate intensity exercises (falling between v1.5 and v2.5) of longer duration (45 minutes) are more effective at enhancing muscle structures associated with stamina and power in sport horses than high intensity (equivalent to v4) and shorter duration (25 minutes) exercises.