Skeletal muscle characteristics and metabolic response to exercise in young standardbreds.
OBJECTIVE
To determine whether performance capacity in a group of young trained Standardbreds is related to skeletal muscle characteristics and metabolic response to exercise.


METHODS
13 clinically normal 2-year-old Standardbreds.


METHODS
Venous blood and middle gluteal muscle biopsy samples were obtained from each horse within 1 to 2 minutes after trotting at high speed for 1,600 m.


RESULTS
There was a positive correlation between plasma lactate and muscle glucose-6-phosphate (G-6-P) concentrations and trotting speed. There was a negative correlation between muscle adenosine triphosphate concentration and trotting speed, plasma lactate concentration, and muscle lactate and G-6-P concentrations. Muscle concentration of G-6-P was positively correlated with muscle lactate and plasma lactate concentrations. Percentage of type-1, -2A, and -2B fibers in skeletal muscle and muscle enzyme activities of hexokinase, 3-OH-acyl-CoA dehydrogenase, lactate dehydrogenase, and citrate synthase were not correlated with trotting speed.


CONCLUSIONS
Speed of trotting at a distance of 1,600 m in young trained Standardbreds is related to the ability of muscle to produce energy by use of anaerobic glycolysis.
Ronéus
N
N
Department of Medicine and Surgery, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Essén-Gustavsson
B
B
D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002950:Citrate (si)-Synthase / Q000378:metabolism; D005260:Female; D019298:Glucose-6-Phosphate / Q000378:metabolism; D006593:Hexokinase / Q000378:metabolism; D006736:Horses / Q000502:physiology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D007773:Lactates / Q000097:blood; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D010805:Physical Conditioning, Animal; D005082:Physical Exertion
D007773:Lactates; D019298:Glucose-6-Phosphate; D000255:Adenosine Triphosphate; D015094:3-Hydroxyacyl CoA Dehydrogenases; D007770:L-Lactate Dehydrogenase; D002950:Citrate (si)-Synthase; D006593:Hexokinase