Effects of training on muscle composition in horses.

This research article investigates the impact of a commercial race-training program on the muscle composition of Thoroughbred horses, using various biochemical and histological analysis methods. The results indicate some significant changes in muscle fiber characteristics and enzymatic activities, while other aspects remained unchanged through the training period.

Methodology and Sample Collection

• The study involved ten Thoroughbred horses undergoing a racing training regimen for 12 weeks.
• Biopsy samples were taken from the middle gluteal muscle of each horse at three different stages: before the onset of the training program, and then after six and twelve weeks of the program.
• Muscle fibers were identified as types I, IIA, IIB, or IIC using histochemical examination of myosin adenosinetriphosphatase after acid or alkaline pre-incubations.
• The number of intermyofibrillar capillaries adjacent to each fiber was determined after staining the samples with the alpha-amylase-periodic acid-Schiff technique.
• The research team also investigated the oxidative capacity of individual fibers using the reduced nicotinamide dinucleotide tetrazolium-reductase stain.

Biochemical Analyses

• The study conducted a fluorometric assessment of three enzymes – citrate synthase, 3-hydroxy-acyl coenzyme A dehydrogenase, and lactate dehydrogenase – which serve as markers of end terminal oxidative, beta-oxidative, and glycolytic potentials, respectively.

Key Findings

• The investigation found that the percentages of different types of muscle fiber did not change significantly in response to the training regimen.
• However, by the end of the 12th week, there was a significant increase in the number of type IIB fibers with high nicotinamide dinucleotide-tetrazolium reductase staining.
• No significant changes were observed in the number of capillaries adjacent to each fiber type during the training period.
• The enzymatic activities of both citrate synthase and 3-hydroxy-acyl coenzyme A dehydrogenase increased significantly after six and twelve weeks of training.
• Conversely, no changes were detected in the levels of lactate dehydrogenase in response to training.