EFFECTS OF SUBJECT VELOCITY ON GROUND REACTION FORCE MEASUREMENTS ANDSTANCE TIMES IN CLINICALLY NORMAL HORSES AT THE WALK AND TROT

Objective-The objective of the study reported here was to evaluate the effects of changing velocity on stance time and ground reaction force (GRF) measurements in horses at the walk and trot. Design-Force plate gait analysis was used to evaluate clinically normal horses at variab le velocities. Ground reaction force measurements and stance times wer e recorded and compared. Animals-12 adult horses. Procedure-Data were obtained from 192 valid trials at the walk and 162 valid trials at the trot. Vertical, braking, and propulsive peak forces and impulses were measured. Pearson's correlation coefficients were determined for velo city and stance time and all measured forces and impulses in the forel imbs and hind limbs. Trials were divided into distinct velocity ranges . Trials obtained at velocities within the established ranges were ana lyzed to evaluate changes in vertical, braking, and propulsive peak fo rces and impulses at differing speeds within the walk and trot gaits. Results-At the walk and trot, a significant negative correlation was f ound between velocity and forelimb and hind limb stance times. Velocit y and stance time were significantly correlated with many of the GRF a nd impulse measurements. Velocity was significantly correlated with ve rtical and braking forces in the hind limbs at the walk, with vertical force in the forelimbs at the trot, and with braking force in the for elimbs and hind limbs at the trot. Velocity and stance time correlated significantly with forelimb and hind limb vertical impulses. Forelimb and hind limb stance times decreased significantly as velocity increa sed. Hind limb braking force increased and forelimb and hind limb vert ical impulses decreased significantly as walk velocity increased. Fore limb braking force increased significantly between velocity ranges at the trot. Conclusions-Results of this study confirm that a significant ly negative linear correlation exists between subject velocity and sta nce times in clinically normal horses at the walk and trot. Significan t correlations were also identified between velocity and many GRF meas urements, indicating that subject velocity does influence the generati on of GRF measurements in horses. Variation in subject velocity should be minimized when performing forceplate analysis in horses.