Increases in Skeletal Muscle Size Following Moderate Vascular Occlusion in Standardbred Horses

Abstract

2343 Moderate vascular occlusion increases muscular activity and can be used in populations that cannot tolerate high intensity exercise to promote muscular growth. PURPOSE: To demonstrate whether moderate vascular occlusion would result in changes to limb muscle size in horses. Methods: Six healthy, unfit Standardbred mares (age 14 ± 4, body mass 529 ± 49 kg, mean ± SD) were used. Horses (standing at rest) wore an occlusion cuff at the most proximal position of the left foreleg. The right foreleg was used as control. An occlusion pressure of 200 mmHg was set for 5 min followed by 10 min recovery. Three sets of occlusions were given to each horse. Ulnaris lateralis/flexor digitorum profundus and extensor digitorum communis muscle thickness were measured using B-mode ultrasound. Foreleg and 1st phalanx circumference was st measured using a flexible-tape measure. Pulse wave Doppler was performed on the radialis artery with a 5–10 mHz mechanical transducer three times at baseline and twice during each occlusion. A final measurement was also obtained 2 to 3 min after removal of the cuff. Peak flow velocity (PFV), and the flow integral (FVI) were measured each time. Results: Mid-foreleg but not 1st phalanx girth was increased (p<0.05) in st the occluded but not the control leg following occlusionFlextensor and flexor MTH was increased (p<0.05) in the occluded but not the control leg. There were no changes (p>0.05) in PFV or FVI at any measured time-point. Conclusion: Moderate vascular occlusion may be a suitable and safe model to study muscle hypertrophy in horses.