Skeletal muscle transcriptome profiles related to different training intensities and detraining in Standardbred horses: a search for overtraining biomarkers.

The researchers investigated how different training intensities and periods of rest (detraining) impact the gene expression patterns in the skeletal muscle of Standardbred horses. They were looking for potential biomarkers to identify overtraining in horses. They found that training intensity greatly impacted muscle-specific protein metabolism and certain cellular mechanisms, with some of these changes persisting even after detraining.

Skeletal Muscle Adaptations and Exercise Intensity

• The research was primarily focused on understanding the changes in gene expression in the skeletal muscles of horses in response to different training intensities. Specifically, the team studied endurance training, sprint training, and a period of detraining.
• The results showed that the intensity of training had a major impact on the skeletal muscle-specific protein metabolism of the horses, leading to increased CO2 export from the tissues.
• Intensive training, in particular, showed an increase in the energy metabolism of the horses and had an effect on the heart and adipose tissues. However, this type of training also exhibited signs of inducing stress, negatively affecting apoptosis (a process of programmed cell death), and compromising immune capacity.

Cell-Cell Contact Mechanisms and Detraining

• Further results pointed towards the relation between training intensity and a decrease in the expression of extracellular matrix (ECM) proteins, cell-cell contacts, and intracellular signalling pathways. Basically, with an increase in training intensity, the gene expression related to cell adhesion and intercellular communication was seen to reduce.
• The study also explored the effects of detraining or resting periods following exercise. It was observed that while most exercise-induced changes were reversed through detraining, some changes persisted. These include modifications related to the heart tissue and increased expression of muscle-specific proteins.
• It was also of particular interest that the changes to the ECM expression and cell-cell contact mechanisms induced by exercise seemed to be long-lasting. These changes were linked to various aspects of both training and detraining periods.

Implications for Overtraining Identification

• The investigation suggested that the prolonged changes to ECM expression and cell-cell contact mechanisms may be potential biomarkers for identifying overtraining. Essentially, these might serve as early signs of muscle overload or overtraining in the horses.
• Such biomarkers could be invaluable in athletic training and in enhancing our understanding of exercise physiology, ultimately assisting in the creation of balanced training programs that enhance performance while ensuring welfare.