Skeletal muscle characteristics and metabolic response to exercise in young standardbreds.

The researchers studied the relationship between muscle features and metabolic response to exercise in Standardbreds, a breed of horse. They found that the speed at which young trained Standardbreds can trot 1,600 meters is tied to how well their muscles can produce energy through a process called anaerobic glycolysis.

Methods of the Study

In conducting the research, the following methods were employed:

• The researchers used a whole group of 13 Standardbreds. These horses were two years old and in good health.
• After each horse had trotted a distance of 1,600 meters at high speed, the researchers collected venous blood and middle gluteal muscle biopsy samples within one to two minutes.

Study Results

The analysis of the data gathered in the study led to the finding of various correlations:

• A positive correlation was found between the plasma lactate and muscle glucose-6-phosphate (G-6-P) concentrations and the speed at which the horses trotted.
• A negative correlation was found between the concentration of muscle adenosine triphosphate and trotting speed, plasma lactate concentration, and muscle lactate and G-6-P concentrations.
• A positive correlation was found between the concentration of muscle G-6-P and muscle lactate and plasma lactate concentrations.
• No correlations were found between the trotting speed and the percentage of type-1, -2A, and -2B fibers in the skeletal muscle, as well as the muscle enzyme activities of hexokinase, 3-OH-acyl-CoA dehydrogenase, lactate dehydrogenase, and citrate synthase.

Conclusions of the Study

The researchers concluded that:

• The ability of a horse’s muscle to produce energy through a process known as anaerobic glycolysis determines the speed at which young Standardbreds can trot a distance of 1,600 meters.
• The study did not find any relationship between the horses’ trotting speed and the number of certain types of muscle fibers or the activities of specific muscle enzymes.